Research ArticleMesoscale Assessment of CO2 Storage Potential and GeologicalSuitability for Target Area Selection in the Sichuan Basin

Yujie Diao12 Guowei Zhu1 Hong Cao2 Chao Zhang2 Xufeng Li2 and Xiaolin Jin2

1State Key Laboratory of Coal Resource and Mine Safety China University of Mining amp Technology Beijing 100083 China2Key Laboratory of Carbon Dioxide Geological Storage Center for Hydrogeology and Environmental Geology SurveyChina Geological Survey Baoding City Hebei Province 071051 China

Correspondence should be addressed to Yujie Diao diaoyujie1983163com

Received 11 January 2017 Revised 14 March 2017 Accepted 26 April 2017 Published 2 July 2017

Academic Editor Meng Lu

Copyright copy 2017 Yujie Diao et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

In China south of the Yangtze River there are a large number of carbon sources while the Sichuan Basin is the largest sedimentarybasin it makes sense to select the targets for CO2 geological storage (CGUS) early demonstration For CO2 enhanced oil and gascoal bedmethane recovery (CO2-EOR EGR and ECBM) or storage in these depleted fields the existing oil gas fields or coal seamscould be the target areas in the mesoscale This paper proposed a methodology of GIS superimposed multisource informationassessment of geological suitability for CO2 enhanced water recovery (CO2-EWR) or only storage in deep saline aquifers Thepotential per unit area of deep saline aquifers CO2 storage in Central Sichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group being the main reservoir CO2 storage potential of depleted gas fields is 5373 times 108 t while itis 3385 times 108 t by using CO2-EGR technology This paper recommended that early implementation of CGUS could be carried outin the deep saline aquifers and depleted gas fields in the Sichuan Basin especially that of the latter because of excellent traps richgeological data and well-run infrastructures

1 Introduction

The Intergovernmental Panel on Climate Change (IPCC)noted in its fifth assessment report that climate change ismore serious than the original understanding and perhapsmore than 95 of it is caused by human behavior [1]In China south of the Yangtze River there are a largenumber of carbon sources among that about 10458MtCO2 are discharged in Sichuan Province and ChongqingCity mainly from cement and thermal power plants [2]Therefore as the largest sedimentary basins in SouthernChina the Sichuan Basin covers about 20 times 104 km2 withits craton basic structure thick marine carbonate andclastic sedimentary strata and has great significance inanalyzing mesoscale potential and geological suitability forCO2 geological utilization and storage technologies (CGUS)including CO2 enhanced oil gas coal bed methane shalegas and water recovery (CO2-EOR EGR ECBM ESGR

and EWR) CO2 enhanced geothermal systems and ura-nium leaching (CO2-EGS and EUL) Furthermore CO2geological storage technologies include depleted oil or gasfields unmineable coal seams and deep saline aquifers CO2storage [3]

Evaluation of CO2 storage potential is required to assessthe contribution towards the reduction of CO2 emissionsThe Carbon Sequestration Leadership Forum (CSLF) andUS Department of Energy (USDOE) both proposed thestandards and methodologies for CO2 storage capacity esti-mation and site selection and also the atlas [4ndash9] whichprovided the basic methodologies Some researchers devel-oped the methodologies or key parameters to evaluate theCO2 storage potential or site selection [10 11] and Goodmanet al [12] provided a detailed description of the USDOErsquosmethodology for CO2 storage potential evaluation In ChinaZhang et al [13] first carried out a preliminary assessmentof the national scale potential of CO2 geological storage

HindawiGeofluidsVolume 2017 Article ID 9587872 17 pageshttpsdoiorg10115520179587872

2 Geofluids

in depleted oil and gas fields unmineable coal seams anddeep saline aquifers Subsequently Liu et al [14] and Liet al [15] carried out evaluation of the potential of CO2geological storage in depleted natural gas fields and deepsaline aquifers respectively Guo et al [16] evaluated thenational scale potential of CO2 geological storage in depletedoil and gas fields unmineable coal seams and deep salineaquifers in 417 onshore and offshore sedimentary basinssupported by China Geological Survey (CGS) and evaluatedthe suitability for prospective selection in the macroscale Asthe CGUS methodologies are paid more and more attentionLi et al [17] preliminary evaluated CO2 geological storagepotential of CO2-EOR EGR and ECBM ACCA21 [3] firstevaluated the national scale potential of CGUS andWei et al[18] developed the methodology of potential assessment ofCO2 geological utilization and storage in the macroscale inChina

From the view of spatial scale and time scale themesoscale corresponds to target between basin and site whichneeds more geological survey for CCUS demonstration orindustrialization in the short term generally before 2030according to carbon reduction target of China Thereforebecause of the large area and complicated geology differentfrom abroad the methodologies and parameters of potentialevaluation of CGUS should be more suitable for geology inthe Sichuan Basin

2 Methodology

In the mesoscale oil and gas fields and CBM fields underproduction could be the target areas for CO2 geologicalutilization or storage However for deep saline aquifer CO2geological storage or CO2-EWR the assessment of potentialand geological suitability for target area selection shouldfollow the order of candidate prospective area to target areabecause of fast changing lithology and strong heterogeneityin terrestrial sedimentary formations and also the differentdistribution of aquifers in lateral and vertical directionBased on the detailed studies of reservoirs and caprocks insedimentary basins and the basic requirements for geologicalsafety the candidate prospective areas in the Sichuan Basinshould be selected first and then potential and geologicalsuitability assessment could be carried out for target areaselection next

21 Method of Assessment of CO2 GeologicalUtilization and Storage Potential

211 Depleted Oil Fields CO2 Storage and CO2-EOR

(1) DepletedOil Fields CO2 StorageThemethod of assessmentof CO2 storage potential of CO2-EOR is as follows [12]

119866CO2

= OOIP120588oil sdot 119861 sdot 120588CO2

sdot 119864oil (1)

where 119866CO2

is CO2 geological storage potential OOIP isthe proven original oil reserves in place of existed oil andgas fields presented by Ministry of Land and Resources

Table 1 The value of EXTRA with different API gravity

EXTRA () API53 lt3113 (APImdash31) + 53 31 le API le 41183 gt41

Table 2 Four EOR cases with different depthpressure and APIgravity

Depth API 119875LCO2() 119875HCO2

()

lt2000 gt35 100 0le35 66 33

gt2000 gt35 33 66le35 0 100

of China (MLR) in accordance with the research scalein this paper 120588oil is oil density at standard atmosphericpressure 119861 is oil volume factor 120588CO

2

is CO2 density atreservoir temperature and pressure conditions (according toBerndt Wischnewski formula) 119864oil is storage efficiency (oreffective coefficient) recommend as 75 by Li et al [17]based on the largest oil production rate of most depleted oilfields in China and the possible amount of CO2 could beinjected

(2) CO2-EOR The method of CO2 geological storage poten-tial assessment of CO2-EOR is as follows [19]

119866CO2-EOR = OOIP

120588oil sdot 119861 sdot 119864oil sdot EXTRAsdot (119875LCO

2

sdot 119877LCO2

+ 119875HCO2

sdot 119877HCO2

) (2)

API = (1415119878119892 ) minus 1315 (3)

where 119866CO2-EOR is storage potential of CO2 by using CO2-

EOR technology EXTRA is the proportion of extra recoveryto OOIP (Table 1) 119875LCO

2

is the lowest probability of oilrecovery (Table 2) 119875HCO

2

is the highest probability of oilrecovery (Table 2) 119877LCO

2

= 2113 tm3 119877HCO2

= 3522 tm3 119878119892is specific gravity other parameters are the same as formula(1)

212 Depleted Gas Fields CO2 Storage and CO2-EGR

(1) Depleted Gas Fields CO2 Storage USDOE [12] and CSLF[5] have the same assumptions for assessments of bothCO2-EGR storage potential and CO2-EOR storage potentialTherefore the calculation formulas are basically the same

119866CO2

= OGIP120588gasstd sdot 119861 sdot 120588CO2

sdot 119864gas (4)

Geofluids 3

Table 3 The values of 119877CO2CH4and 119862 of different types of coal

(USDOE 2003)

Types of coal 119877CO2CH4119862

Lignite 10 100Noncaking coal 10 067Weakly caking coal 10 100Long flame coal 6 100Gas coal 3 061Fat coal 1 055Coking coal 1 050Lean coal 1 050Meager coal 1 050Anthracite 1 050

Table 4 Storage efficiency of unmineable coal seams [12]

11987510 11987550 1198759021 37 48

where OGIP is the proven original natural gas reserves inplace similar to OOIP 120588gasstd is gas density under standardatmospheric pressure 119861 is natural gas volume factor 119864gasis storage efficiency (effective coefficient) 75 [17] otherparameters are the same as formula (1)

(2) CO2-EGR Whether the feasibility of CO2-EGR techniqueis possible or not we could evaluate the storage potential ofCO2 using the following formula

119866CO2-EGR = OGIP120588gasstd sdot 119861 sdot 120588CO2

sdot 119864gas sdot 119862 (5)

where 119866CO2-EGR is CO2 geological storage potential by using

CO2-EGR technology 119862 is reduction coefficient comparedwith depleted gas storage Li et al recommend it as 63 [17]other parameters are the same as formula (4)

213 Unmineable Coal Seams CO2 Storage and CO2-ECBM

(1) Unmineable Coal Seams CO2 Storage The formula tocalculate the storage potential is as follows

119866CO2

= 119866CBM sdot 119877CO2CH

4

sdot 120588CO2std sdot 119864coal (6)

where 119866CBM is coal bed methane reserves (there is onlyprospective reserves proposed byMLR less credible than theoil and gas reserves)119877CO

2CH

4

is the absorption capacity ratioof CO2 and CH4 in coal seams 119864coal is storage efficiency(effective coefficient) other parameters are the same asformula (4)

The values of 119877CO2CH

4

and 119864coal were proposed byUSDOE (2003) and Goodman et al [12] as shown in Tables 3and 4

Table 5 CO2 storage efficiency coefficients 119864saline at regional scales[12]

Lithology 11987510 11987550 11987590Clastics 12 24 41Dolomite 20 27 36Limestone 13 20 28

(2) CO2-ECBMThe formula to calculate the storage potentialof CO2-ECBM is as follows

119866CO2-ECBM = 119866CBM sdot 119877CO

2CH

4

sdot 120588CO2std sdot 119864coal sdot 119862 (7)

where119866CO2-ECBM is CO2 geological storage potential by using

CO2-ECBM technology 119862 is recovery coefficient of differenttypes of coal other parameters are the same as formula(6)

214 Deep Saline Aquifers CO2 Storage and CO2-EWR Thecalculation formulas of CO2-EWR and the only geologicalstorage in saline aquifers technology are the same as follows

119866CO2

= 119860 sdot ℎ sdot 120593119890 sdot 120588CO2

sdot 119864saline (8)

where119860 is reservoir distribution area ℎ is reservoir thickness120593119890 is saline aquifer average effective porosity 119864saline is storageefficiency (effective coefficient) shown in Table 5 otherparameters are defined above

22 Method of Suitability Assessment forSaline Aquifers Storage Target Selection

221 Mathematical Model

(1) GIS Superimposed Multisource Information AssessmentTechnology Superimposed multisource information assess-ment technology is an integrated method of processingmultisource geological data Based on the two-dimensionalspace determined by geographical coordinates the unity ofthe geographical coordinates within the same region but withdifferent information that is the so-called spatial registra-tion is achieved which is performed by using geographicinformation software (ArcGIS or MapGIS)

(2) Mathematical Model The selected candidate prospectiveareas undergo the GIS spatial analysis into grids of 1000mtimes 1000m The thematic information map prepared for eachfactor is screened by key veto factors Thus the single factorunfit to carry out CO2 geological storage is identified toabandon the unsuitable grid for deep saline aquifer CO2storage

4 Geofluids

Table6Indexsyste

mforg

eologicalsuitabilityassessmenttoselectsuitabletargetsford

eepsalin

eaqu

iferC

O2sto

rage

Levelone

index

Weight

Leveltwoindex

Weight

Levelthree

index

Weight

Goo

dGeneral

Poor

Keyveto

factor

Reservoir

cond

ition

sand

storage

potential

050

Characteris

ticof

theb

estreservoir

060

Litholog

y007

Clastic

Mixof

clasticand

carbon

ate

Carbo

nate

Sing

lelayer

thickn

essh

m011

ge8030lehlt8

010lehlt3

0lt10

Sedimentary

facies

036

Riverdelta

Turbidityallu

vial

fan

Beachbarreef

Averagep

orosity

120593020

ge1510le120593lt15

5le120593lt10

lt5Av

erage

perm

eability119896m

D027

ge5010leklt5

01le

klt10

lt1Storagep

otentia

l040

Storagep

otentia

lperu

nitareaG

(104

tkm2)

100

ge100

10leGlt10

0lt10

Geologicalsafety

050

Characteris

ticof

them

aincaprock

062

Litholog

y030

Evaporites

Argillite

Shalea

nddense

limestone

Thickn

essh

m053

ge100

50lehlt10

010lehlt5

0lt10

Depth

Dm

011

1000leDle2

700

lt1000

gt2700

Bufferc

aprock

abovethe

main

caprock

006

Multip

lesets

Sing

leset

Non

e

Hydrodynamic

cond

ition

s024

Hydrodynamic

cond

ition

s10

0Groun

dwater

high

-con

tainment

area

Groun

dwater

containm

entarea

Groun

dwater

semicon

tainment

area

Groun

dwater

open

area

Seism

icactiv

ity014

Peak

grou

ndacceleratio

n050

lt005

g005

g010g

015g020

g030

gge0

40g

Develo

pment

degree

offractures

050

Simple

Mod

erate

Com

plex

With

in25

kmof

activ

efaults

Geofluids 5

Then GIS spatial analysis and evaluation are carried outusing formula (9)

119875 = 119899sum119894=1

119875119894119860 119894 (119894 = 1 2 3 119899) (9)

Here P is suitability scores of unit for CO2 geological storage119899 is the total number of evaluation factors 119875119894 is given point ofthe factor 119894 119860 119894 is index weight of the factor 119894

Single metric suitability rating is as follows ldquogoodrdquo 9points ldquogeneralrdquo 5 points and ldquopoorrdquo 1 pointThe evaluationresult suitability rating is as follows ldquohighly suitablerdquo valuerange 7 le P le 9 ldquosuitablerdquo 5 le P lt 7 ldquoless suitablerdquo 3 le P lt 5and ldquounsuitablerdquo 1 le P lt 3222 Index System for Geological Suitability Assessment Asshown in Table 6 the index system for geological suitabilityhas three hierarchies The index weights at all levels aredetermined using the Analytic Hierarchy Process (AHP) [2021]

The assessment indexes are described detailed in thefollowing

(1) Characteristic of the Best Reservoir

Depth Only if the theoretical storage depth is more than 800meters can CO2 enter the supercritical state normally lowthan 3500 meters

Lithology According to the existing commercial-scale CO2geological storage projects (eg [22ndash24]) reservoir charac-teristics of oil and gas fields inChina [25] and the engineeringverification by the Shenhua CCS demonstration project inthe Ordos Basin in China [26] clastic reservoirs are generallybetter than carbonate reservoirs

Single Layer Thickness Because of terrestrial sedimentaryfacies in most formations in onshore basins of China it isdifficult to find the large thick aquifers forCO2 storage similaras Sleipner project in Norway The minimum single layerthickness of reservoirs recommended in this paper is 10m

Sedimentary Facies Most Cenozoic sedimentary basins inChina are terrestrial sedimentary formations The main partof the reservoir is the deltaic sand body followed by theturbidite sand and alluvial fan glutinite body and finally thesand beach dams and a small amount of reef

Porosity and Permeability Low porosity and permeability is aspecial feature in terrestrial sedimentary oil and gas reservoirsand saline aquifers in China Generally for both the clasticand carbonate rock reservoirs the porosity should be greaterthan or equal to 5 and permeability should be greater thanor equal to 1mD (eg [27ndash30])

(2) Characteristic of the Main Caprock

Lithology The most common caprocks of oil and gas fieldsin China are argillite (mudstone and shale) and evapor-ites (gypsum and rock salt) followed by carbonate rocks

(marl argillaceous dolomite compact limestone and densedolomite) and frozen genesis caps Sometimes there are localchert layers seams dense volcanic rocks and intrusive rockcaps

ThicknessThere are certain relationships between cap thick-ness and the size and height of the reservoir With thecombination of existing cap thickness grading standards [30]and considerations of the differences between CO2 and oiland gas the reference criteria for grading the classificationof CO2 geological storage cap thickness can be specifiedThe minimum thickness of CO2 geological storage caprocksrecommended in this paper is 10m

Burial Depth The cap type is argillaceous rocks The diage-nesis has different effects on the performance of the caprockat different stage [31] When the burial depth of argillaceousrocks is less than 1000m the diagenetic degree is poor and thesealing mainly relies on the capillary pressure The porosityand permeability are good but with poor plasticity At theburial depth of 1000ndash2700m the diagenesis is enhancedmineral particles inside the argillaceous rock become morecompacted the porosity and permeability deteriorate theplasticity increases the capillary flow capacity declines seal-ing ability improves and there is abnormal sealing pressureWhen the burial depth is greater than 2700m it is equiv-alent to the tightly compacted stage of the Argillite Thediagenesis is boosted further the plasticity decreases andfragility increases with the increase in the abnormal pressuremicrocracks appear on the argillaceous rocks and capillarysealing ability deteriorates

The ldquoBuffer Caprdquo above the Main Caprock When the CO2breaks through the main cap the ldquobuffer caprdquo above the maincap has to provide a certain sealing capability to reduce orprevent the escape of CO2

(3) Geological Safety

Hydrodynamic Conditions Ye et al [32] divided the effectof hydrogeological conditions controlling coalbed methaneinto three categories hydraulic transport dissipation effecthydraulic seal effect and hydraulic block effect The moreclosed the hydrogeological conditions are themore favorablethey are for CO2 geological storage Basin lots with complexgeological structure and powerful water alternating are notsuitable CO2 geological storage candidate prospective areasdue to the high degree of hydrogeology and strong ground-water activities

Peak Ground Acceleration The GB 18306-2001 ldquoThe PeakGround Acceleration Zoning in Chinardquo shows the Chineseseismic zonation map its technical elements and user provi-sions It also applies to the CO2 geological storage construc-tion project The greater the peak ground acceleration is themore unfavorable it is for CO2 geological storage In generalthe peak ground acceleration should be less than 040 gBesides active faults are not only CO2 leakage pathways butalso cause damage to the strata continuity resulting in CO2

6 Geofluids

01 50 100 150 200 250 300 350

100

200

300

400

500

Number of basins

Stor

age p

oten

tial (

km2)

Figure 1 The statistical profile of CO2 geological storage potential per square kilometer of 390 onshore basins in China

leakage through the caprock According to the GB 17741-2005ldquoProject site seismic safety evaluationrdquo [33] the identificationof the capable fault has to be made within a 5 km range of thefirst class venues and epitaxy For seismic safety evaluationthe near-field region should be extended to a radius of 25 kmrange Therefore areas within 25 km of the active faults areinappropriate as the candidate prospective areas

Development Degree of Fractures CO2 could leak by tectonicpathways including faults fractures and ground fissures (eg[28 34ndash36]) Due to the complexity of geological structureand faults development in the Sichuan Basin the qualitativeassessment is based on the faults development and theexisting seismic data The more complex the fault systemis the more unfavorable it is for CO2 geological storage Inaddition there have been more frequent seismic activities inthe Sichuan Basin in recent years

(4) Storage Potential per Unit Area Guo (2014) evaluated thenational scale potential of CO2 geological storage in deepsaline aquifers of 390 onshore basins in China supported byChina Geological Survey As shown in Figure 1 the potentialof CO2 geological storage in deep saline aquifers in most ofthe sedimentary basins is 50 times 104ndash100 times 104 t generally anda small part of the basins are less than 10 times 104 t or more than100 times 104 t3 Candidate Prospective Areas for CO2Geological Utilization and Storage

The fine forming conditions of the reservoir mediums foroil gas and CBM make them possible that the existing oiland gas fields under production are the mesoscale candidateprospective areas or target areas in the short future Becauseof no official basin-scale data available the CO2 storagepotential of other CO2 geological utilization technologies isnot discussed further in this paper

31 Geology

311 Geostructure As shown in Figure 2 [37] the currentgeostructure of the Sichuan Basin consists of the Southeast

Table 7 Proven OGIP of 27 natural gas fields in the Sichuan Basin

Gas fields OGIP108m3

Puguang 405079Guangrsquoan 135558Hecuan 118706Datianchi 106755Xinchang 84302Luojiazhai 79736Moxi 70231Wolonghe 40886Weiyuan 40861Tieshanpo 37397Dukouhe 359Bajiaochang 35107Luodai 32383Qiongxi 32325Qilibei 28221Baimamiao 26872Dachigan 25871Gaofengchang 22726Qilixia 22548Hebaochang 22212Tieshan 18782Zhongba 1863Majing 17558Xindu 17532Chongxi 13635Fuchengzhai 1033Jiannan 10025

Sichuan fold belt Central Sichuan low uplift and NorthwestSichuan depression

312 Stratigraphy The Sichuan Basin sedimentary strata arecomplete with a total thickness of 6000ndash12000m Only thePermian and the younger strata are considered in this paperas follows from old to new

Geofluids 7

III1

III1

III2

Southeast Sichuan fold belt

Central Sichuan low uplift

Northwest Sichuan depression

Longmen Mountai

n fault z

one

Long

quan

Mou

ntain

faul

t zon

e

Huayin Mountain

fault z

one

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Tectonic units

First-order tectonic units

Second-order tectonic units

0 50 100 (km)

Gas fields

Oil fields

Faults

II1

II2

I2

I1

AZhongbaGas Field

Huaying MountainZhangjiachang

Gas FieldDachiganjing

Gas Field

FangdoushanMountain

B

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

WolongheGas Field

300∘ang

Figure 2 Sichuan Basin geological structure unit zoning map There are three first-order tectonic units in the Sichuan Basin that is theSoutheast Sichuan fold belt the Central Sichuan low uplift and the Northwest Sichuan depression The Southeast Sichuan fold belt consistsof the high steep fold belt in Eastern Sichuan (I1) and the low steep bottom fold belt in Southern Sichuan (I2) the Central Sichuan low upliftis composed of the flat fold belt in Central Sichuan (II1) and the low steep fold belt in Southwestern Sichuan (II2) the Northwest Sichuandepression consists of the low-lying fold belt in Northern Sichuan (III1) and the low steep fold belt in Western Sichuan (III2)

(1) The Permian Liangshan group (P1l) Qixia group(P2q) Maokou group (P2m) Longtan group (P3l)and Changxing group (P3c)

(2) The Triassic Feixianguan group (T1f ) Jialing Group(T1j) Leikoupo group (T2l) Tianjingshan group(T2t) Marsquoantang group (T3m) Xiaotangzi group(T3t) and Xujiahe group

(3) The Jurassic Ziliujing group (J1z) Qianfoya group(J2q) Shaximiao group (J2s) Suining group (J3s) andPenglaizhen group (J3p)

(4) The Cretaceous (K) and the Quaternary (Q)

313 Hydrodynamic Condition The Sichuan Basin is essen-tially an artesian basin dominated by Permian and Triassic

8 Geofluids

Chengdu

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Highly confined aquifers

Confined aquifers

Semiconfined aquifers

Open aquifers

Groundwater flow direction

First-order tectonic units

Second-order tectonic units

0 50 100(km)

I

I

II

II

II

II

II

II

III

III

III

IIIIII

III

IV

IV

IV

Leshan

Figure 3 Hydrodynamic conditions in the Sichuan Basin The groundwater activities are very strong in the peripheral target exposure areaIn contrast the groundwater activities inside the basin are relatively weak with better hydrogeological confinement On the edge of themountain around the Sichuan Basin and the eastern fold belt experiencing infiltration of fresh water due to the complex structure and strongwater alternating

strata The upper Jurassic and Cretaceous formations aremostly a large set of terrestrial clastic sedimentary rocks withred sandstones and mudstones throughout the basin Theyare extremely thick with poor permeability generally lowin moisture but exceedingly uneven which could be goodcaprocks for the reservoirs below them The lower upperTriassic Xujiahe consists of sandstones and shale and thesandstone may be good aquifers for CO2 geological storagedue to its huge thickness The lower and middle Triassicand Permian carbonate rocks are the main saline aquifersin which Triassic carbonate rocks often form alternate layerswith evaporites Therefore an aqueous rock series based onmany stacked white aquifers is formed in the Sichuan Basin(Figure 3)

314 Geological Safety There are many late Quaternaryactive faults on the boundary of the Sichuan Basin forexample the Longmenshan fault zone in NorthwesternSichuan has experienced more intense activity in recentyears It is the induced fracture of the ldquo512rdquo Wenchuan 80earthquake The Lushan 70 earthquake on April 20 2013 is

another devastating earthquake that followed the Wenchuan80 earthquake nearly five years later It is also closely linkedwith the Longmenshan fault belt

However the crust in the Central and Eastern SichuanBasin is more stable Historical earthquakes with magnitudeabove 6 mainly took place in Western Sichuan and South-western Sichuan Basin And the peak ground accelerationzoning according to the GB 18306-2001 ldquoThe Peak GroundAcceleration Zoning in Chinardquo is shown in Figure 4

32 Oil and Gas Fields The Sichuan Basin has abundantnatural gas resources mainly in Eastern Sichuan but arelatively small amount of oil resources The petroleumgeological reserves in the Sichuan Basin amount to 438 times108 t and only 075 times 108 t of proven OOIP in Central andNorthern Sichuan flat structure area [38]

By the end of 2008 theMinistry of Land and Resources ofChina (MLR) announced 125 gas fields in the Sichuan Basin(Figure 1) and the total amount of proven OGIP is 1722502times 108m3 Among them there are 27 medium to large-sizedconfirmed gas fields with OGIP exceeding 100 times 108m3 of

Geofluids 9

gt015 g

gt015

g

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Seismic peak ground acceleration First-order tectonic units

Second-order tectonic unitsHistorical earthquakes (M 6ndash69)

010 gndash015g

lt005 g

lt005 g

lt005 g

lt005 g

gndash010g005

0 50 100(km)

Figure 4 Seismic peak ground acceleration and large historical earthquakes in the Sichuan Basin The peak ground acceleration is less than010 g in most parts of the Sichuan Basin Only in the western margin of the Sichuan Basin the peak ground acceleration is larger than 015 g

which the total natural gas reserves are 1509268 times 108m3accounting for 876 of the total proven OGIP in the basin(Table 7)

33 Unmineable Coal Seams The CBM geological reservesin the Sichuan Basin amount to 347140 times 108m3 in Sichuanprovince and Chongqing city 508457 times 108m3 in SouthernSichuan province and Northern Guizhou province respec-tively from 1000 to 2000meters depth [39] Among these thecoalfields in Southern Sichuan province are the most abun-dant accounting for 82 of the provincersquos total resources

34 Deep Saline Aquifers Comparedwith oil fields gas fieldsand unmineable coal seams the analysis of geological condi-tions for saline aquifers CO2 geological storage is muchmorecomplex The CO2 geological storage candidate prospectivearea for deep saline aquifers CO2 storage was selected fromthe map projection on the ground of all potential under-ground CO2 reservoirs In addition the hydrodynamic andgeological safety conditions must be studied to delineate thecandidate prospective areas

341 Candidate Prospective Area Delineation Standards Asmentioned above this report presents the delineation stan-dards of the CO2 geological storage candidate prospective

Table 8 Veto over key factors of CO2 geological storage candidateprospective areas delineation

Key factors VetoReservoir conditions

Layer thickness lt10mPorosity lt5Permeability lt1mD

Hydrogeological conditionsFormation water salinity lt3 gLGroundwater hydrodynamic condition Groundwater zone

Geological safety conditionsActive faults lt25 kmPeak ground acceleration ge040 g

areas shown in Table 8 Further potential and suitabilityassessments can be carried out for target area selection

342 Vertical Reservoir Cap Combination and CandidateProspective Areas Distribution The reservoirs for deep salineaquifer CO2 storage consist of the Permian the lower Triassiccarbonates and upper Triassic and Jurassic clastic reservoirs(Figure 5)The reservoir space includes carbonate karst poresand cracks and clastic pores and cracks Overall all reservoirs

10 Geofluids

Geochronology

Series Formation

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Penglaizhen

Suining

Shaximiao

Qianfoya

Ziliujing

Six

Xiaotangzi

Marsquoantang

Tianjingshan

Leikoupo

Changxing

Longtan

Maokou

Qixia

LiangshanCarbon-iferous

Permian

Upper

Stata

Middle

Lower

Upper

Upper

Middle

Middle

Lower

Lower

Five

Four

Three

Two

One

Four

Three

Two

One

Five

Four

Three

Two

One

Litho-histogram

D

depr

essio

nrift

Sandstone

Mudstone

Mud sandstone

Limestone

Dolomite

Reservoir

Caprock

Thick-ness(m)

Poro-sity()

Perme-ability(mD)

Coverage

Local

Regional

Regional

Regional

1244

5Local

Average

5Local

AverageLocal

10 5Local

10 5Local

Porefracture

Reservoirspace

fracture

Porefracture

Porefracture

Dissolved porefracture

Fracture-cave

Fracture-cave

Porefracture

525Average

605AverageLocal

Average

Dissolved pore

Dissolved pore

Rese

rvoi

r

Capr

ock

Tect

onic

mov

emen

tBa

sinev

olut

ion

Mid

dle Y

ansh

an

Fore

land

Late

Indo

sinia

n

Intr

acra

toni

c

ongw

u

Pore

001ndash10

gt1

gt200

gt1

gt1gt6

gt7

gt1

gt1

gt8gt10

gt1

gt1

gt1725

4ndash10

6ndash80

25ndash70

25ndash30

100ndash200

100ndash200

0ndash300

Jialin

gjia

ngFe

ixia

ngua

nXu

jiahe

Figure 5 CO2 geological storage vertical reservoir cap combination in the Sichuan Basin There are nine sets of reservoirs in the SichuanBasin and the section four of Xujiahe group is the primary reservoir with large thickness and area which almost cover the whole basin

Geofluids 11

Table 9 Storage potential of CO2 geological storage in depleted oil fields

Tectonic unit OOIP108 t Oil density(kgm3) 119861 (mdash) Reservoir

pressureMpaOil

temperature∘C120588CO2

(kgm3)119864oil 119866CO2

108 t

Central Sichuan flatstructure area 058 850 118 2126 6442 71263 075 057

Northern Sichuan flatstructure area 017 850 118 2126 6442 71263 075 017

Table 10 CO2-EOR geological storage potential in the Sichuan Basin

Tectonic unit API EXTRA () 119875LCO2() 119875HCO2

() 119864oil 119866CO2-EOR108 t

Central Sichuan flatstructure area 3497 1046 33 66 075 016

Northern Sichuan flatstructure area 3497 1046 33 66 075 005

in the Sichuan Basin have poor physical properties withultra-low porosity and low permeability Comparing withthe natural gas fields in the Sichuan Basin these reservoirsfor CO2 storage have better caprock conditions too Forexample the extensive deposits of gypsum rocks in theLeikoupo phase and the widely developed dark mudstone inthe Lower Jurassic can provide good sealing conditions forthe underlying reservoirs

(1) The Permian The reef flat facies on the top of Qixiagroup form a good reservoir through dolomitization withfavorable reservoir conditions (P2q) [40] Part of them formthe natural gas reservoirs with a thickness of approximately10m Similar to the Qixia group the Maokou group (P2m)is a fracture-cave type of reservoir Changxing group (P3c)reservoirs are pore type and fracture-pore type The porosityis generally 203ndash1585 with an average value of 525 thepermeability is less than 1000mD with an average value of605mD The reservoir thickness is large with a monolayerthickness of 05ndash5m and a single well cumulative thicknessof 25ndash70m [41]

(2) The Triassic The Feixianguan group (T1f ) is similar tothe Changxing groupThe quality and distribution of the reefbeach reservoir are mainly controlled by sedimentary faciesand diagenesis The evaporative platform oolitic dolomitereservoir is mainly distributed in Northeast Sichuan witha monolayer thickness of 15ndash15m and total thickness of20ndash50m The porosity ranges from 2 to 268 on theaverage of 829 and the permeability is less than 1160mDwith an average value of 5973mD The porosity of the openplatform edge oolitic dolomite reservoir is 205ndash2262 onthe average of 842 and the permeability is less than 410mDwith an average value of 1725mD The reservoir monolayerthickness is generally 05ndash6m and the total thickness is10ndash45m typically

The favorable Jialingjiang reservoir facies are the platforminterior shoal and the platform margin shoal facies Forexample section five of Jialingjiang reservoirs consists oflimestone and dolomite with a thickness of 25ndash30m ofwhich approximately 60 is the porosity layer and the

average of the porosity is 5 with the highest value reaching18

The sandstone aquifers in section two section four andsection six of Xujiahe formation could be reservoirs for CO2geological storage composed of residual intergranular poreintergranular dissolved pore and fracture The sand ratioof the sandstones is greater than 70 in 80 generally Inaddition the porosity of section four is higher than sectiontwo and section six usually between 5ndash10 while theporosity of sandstones in section two and section is less than7 generally

Figure 6 shows the candidate prospective areas in theSichuan Basin in the Sichuan Basin for deep saline aquiferCO2 storage based on geology study

4 Results

41 Potential

411 Depleted Oil Fields CO2 Storage and CO2-EOR Theprimary CO2-EOR prospective areas in the Sichuan Basinare located in the flat tectonic area in Central and NorthernSichuan Basin As shown in Tables 9 and 10 the CO2geological storage potential of storage in depleted oil fieldsis only 074 times 108 t while the storage potential is about 021 times108 t by using CO2-EOR technology

412 Depleted Gas Fields CO2 Storage and CO2-EGR TheCO2 geological storage potential of depleted gas fields is 5373times 108 t By using CO2-EGR technology the Sichuan Basin gasfields could achieve CO2 geological storage of 3385 times 108 tAmong that 27 large and medium gas fields have the greatestpotential with the possibility of achieving a CO2 geologicalstorage capacity of 4239 times 108 t in depleted gas fields whilethe storage potential is about 2670 times 108 t by using CO2-EGRtechnology

413 Unmineable Coal Seams CO2 Storage and CO2-ECBMThe Sichuan Basin has abundant coal bedmethane resourcesAs shown in Table 11 the total CO2 geological storage

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

Geofluids 3

Table 3 The values of 119877CO2CH4and 119862 of different types of coal

(USDOE 2003)

Types of coal 119877CO2CH4119862

Lignite 10 100Noncaking coal 10 067Weakly caking coal 10 100Long flame coal 6 100Gas coal 3 061Fat coal 1 055Coking coal 1 050Lean coal 1 050Meager coal 1 050Anthracite 1 050

Table 4 Storage efficiency of unmineable coal seams [12]

11987510 11987550 1198759021 37 48

where OGIP is the proven original natural gas reserves inplace similar to OOIP 120588gasstd is gas density under standardatmospheric pressure 119861 is natural gas volume factor 119864gasis storage efficiency (effective coefficient) 75 [17] otherparameters are the same as formula (1)

(2) CO2-EGR Whether the feasibility of CO2-EGR techniqueis possible or not we could evaluate the storage potential ofCO2 using the following formula

119866CO2-EGR = OGIP120588gasstd sdot 119861 sdot 120588CO2

sdot 119864gas sdot 119862 (5)

where 119866CO2-EGR is CO2 geological storage potential by using

CO2-EGR technology 119862 is reduction coefficient comparedwith depleted gas storage Li et al recommend it as 63 [17]other parameters are the same as formula (4)

213 Unmineable Coal Seams CO2 Storage and CO2-ECBM

(1) Unmineable Coal Seams CO2 Storage The formula tocalculate the storage potential is as follows

119866CO2

= 119866CBM sdot 119877CO2CH

4

sdot 120588CO2std sdot 119864coal (6)

where 119866CBM is coal bed methane reserves (there is onlyprospective reserves proposed byMLR less credible than theoil and gas reserves)119877CO

2CH

4

is the absorption capacity ratioof CO2 and CH4 in coal seams 119864coal is storage efficiency(effective coefficient) other parameters are the same asformula (4)

The values of 119877CO2CH

4

and 119864coal were proposed byUSDOE (2003) and Goodman et al [12] as shown in Tables 3and 4

Table 5 CO2 storage efficiency coefficients 119864saline at regional scales[12]

Lithology 11987510 11987550 11987590Clastics 12 24 41Dolomite 20 27 36Limestone 13 20 28

(2) CO2-ECBMThe formula to calculate the storage potentialof CO2-ECBM is as follows

119866CO2-ECBM = 119866CBM sdot 119877CO

2CH

4

sdot 120588CO2std sdot 119864coal sdot 119862 (7)

where119866CO2-ECBM is CO2 geological storage potential by using

CO2-ECBM technology 119862 is recovery coefficient of differenttypes of coal other parameters are the same as formula(6)

214 Deep Saline Aquifers CO2 Storage and CO2-EWR Thecalculation formulas of CO2-EWR and the only geologicalstorage in saline aquifers technology are the same as follows

119866CO2

= 119860 sdot ℎ sdot 120593119890 sdot 120588CO2

sdot 119864saline (8)

where119860 is reservoir distribution area ℎ is reservoir thickness120593119890 is saline aquifer average effective porosity 119864saline is storageefficiency (effective coefficient) shown in Table 5 otherparameters are defined above

22 Method of Suitability Assessment forSaline Aquifers Storage Target Selection

221 Mathematical Model

(1) GIS Superimposed Multisource Information AssessmentTechnology Superimposed multisource information assess-ment technology is an integrated method of processingmultisource geological data Based on the two-dimensionalspace determined by geographical coordinates the unity ofthe geographical coordinates within the same region but withdifferent information that is the so-called spatial registra-tion is achieved which is performed by using geographicinformation software (ArcGIS or MapGIS)

(2) Mathematical Model The selected candidate prospectiveareas undergo the GIS spatial analysis into grids of 1000mtimes 1000m The thematic information map prepared for eachfactor is screened by key veto factors Thus the single factorunfit to carry out CO2 geological storage is identified toabandon the unsuitable grid for deep saline aquifer CO2storage

4 Geofluids

Table6Indexsyste

mforg

eologicalsuitabilityassessmenttoselectsuitabletargetsford

eepsalin

eaqu

iferC

O2sto

rage

Levelone

index

Weight

Leveltwoindex

Weight

Levelthree

index

Weight

Goo

dGeneral

Poor

Keyveto

factor

Reservoir

cond

ition

sand

storage

potential

050

Characteris

ticof

theb

estreservoir

060

Litholog

y007

Clastic

Mixof

clasticand

carbon

ate

Carbo

nate

Sing

lelayer

thickn

essh

m011

ge8030lehlt8

010lehlt3

0lt10

Sedimentary

facies

036

Riverdelta

Turbidityallu

vial

fan

Beachbarreef

Averagep

orosity

120593020

ge1510le120593lt15

5le120593lt10

lt5Av

erage

perm

eability119896m

D027

ge5010leklt5

01le

klt10

lt1Storagep

otentia

l040

Storagep

otentia

lperu

nitareaG

(104

tkm2)

100

ge100

10leGlt10

0lt10

Geologicalsafety

050

Characteris

ticof

them

aincaprock

062

Litholog

y030

Evaporites

Argillite

Shalea

nddense

limestone

Thickn

essh

m053

ge100

50lehlt10

010lehlt5

0lt10

Depth

Dm

011

1000leDle2

700

lt1000

gt2700

Bufferc

aprock

abovethe

main

caprock

006

Multip

lesets

Sing

leset

Non

e

Hydrodynamic

cond

ition

s024

Hydrodynamic

cond

ition

s10

0Groun

dwater

high

-con

tainment

area

Groun

dwater

containm

entarea

Groun

dwater

semicon

tainment

area

Groun

dwater

open

area

Seism

icactiv

ity014

Peak

grou

ndacceleratio

n050

lt005

g005

g010g

015g020

g030

gge0

40g

Develo

pment

degree

offractures

050

Simple

Mod

erate

Com

plex

With

in25

kmof

activ

efaults

Geofluids 5

Then GIS spatial analysis and evaluation are carried outusing formula (9)

119875 = 119899sum119894=1

119875119894119860 119894 (119894 = 1 2 3 119899) (9)

Here P is suitability scores of unit for CO2 geological storage119899 is the total number of evaluation factors 119875119894 is given point ofthe factor 119894 119860 119894 is index weight of the factor 119894

Single metric suitability rating is as follows ldquogoodrdquo 9points ldquogeneralrdquo 5 points and ldquopoorrdquo 1 pointThe evaluationresult suitability rating is as follows ldquohighly suitablerdquo valuerange 7 le P le 9 ldquosuitablerdquo 5 le P lt 7 ldquoless suitablerdquo 3 le P lt 5and ldquounsuitablerdquo 1 le P lt 3222 Index System for Geological Suitability Assessment Asshown in Table 6 the index system for geological suitabilityhas three hierarchies The index weights at all levels aredetermined using the Analytic Hierarchy Process (AHP) [2021]

The assessment indexes are described detailed in thefollowing

(1) Characteristic of the Best Reservoir

Depth Only if the theoretical storage depth is more than 800meters can CO2 enter the supercritical state normally lowthan 3500 meters

Lithology According to the existing commercial-scale CO2geological storage projects (eg [22ndash24]) reservoir charac-teristics of oil and gas fields inChina [25] and the engineeringverification by the Shenhua CCS demonstration project inthe Ordos Basin in China [26] clastic reservoirs are generallybetter than carbonate reservoirs

Single Layer Thickness Because of terrestrial sedimentaryfacies in most formations in onshore basins of China it isdifficult to find the large thick aquifers forCO2 storage similaras Sleipner project in Norway The minimum single layerthickness of reservoirs recommended in this paper is 10m

Sedimentary Facies Most Cenozoic sedimentary basins inChina are terrestrial sedimentary formations The main partof the reservoir is the deltaic sand body followed by theturbidite sand and alluvial fan glutinite body and finally thesand beach dams and a small amount of reef

Porosity and Permeability Low porosity and permeability is aspecial feature in terrestrial sedimentary oil and gas reservoirsand saline aquifers in China Generally for both the clasticand carbonate rock reservoirs the porosity should be greaterthan or equal to 5 and permeability should be greater thanor equal to 1mD (eg [27ndash30])

(2) Characteristic of the Main Caprock

Lithology The most common caprocks of oil and gas fieldsin China are argillite (mudstone and shale) and evapor-ites (gypsum and rock salt) followed by carbonate rocks

(marl argillaceous dolomite compact limestone and densedolomite) and frozen genesis caps Sometimes there are localchert layers seams dense volcanic rocks and intrusive rockcaps

ThicknessThere are certain relationships between cap thick-ness and the size and height of the reservoir With thecombination of existing cap thickness grading standards [30]and considerations of the differences between CO2 and oiland gas the reference criteria for grading the classificationof CO2 geological storage cap thickness can be specifiedThe minimum thickness of CO2 geological storage caprocksrecommended in this paper is 10m

Burial Depth The cap type is argillaceous rocks The diage-nesis has different effects on the performance of the caprockat different stage [31] When the burial depth of argillaceousrocks is less than 1000m the diagenetic degree is poor and thesealing mainly relies on the capillary pressure The porosityand permeability are good but with poor plasticity At theburial depth of 1000ndash2700m the diagenesis is enhancedmineral particles inside the argillaceous rock become morecompacted the porosity and permeability deteriorate theplasticity increases the capillary flow capacity declines seal-ing ability improves and there is abnormal sealing pressureWhen the burial depth is greater than 2700m it is equiv-alent to the tightly compacted stage of the Argillite Thediagenesis is boosted further the plasticity decreases andfragility increases with the increase in the abnormal pressuremicrocracks appear on the argillaceous rocks and capillarysealing ability deteriorates

The ldquoBuffer Caprdquo above the Main Caprock When the CO2breaks through the main cap the ldquobuffer caprdquo above the maincap has to provide a certain sealing capability to reduce orprevent the escape of CO2

(3) Geological Safety

Hydrodynamic Conditions Ye et al [32] divided the effectof hydrogeological conditions controlling coalbed methaneinto three categories hydraulic transport dissipation effecthydraulic seal effect and hydraulic block effect The moreclosed the hydrogeological conditions are themore favorablethey are for CO2 geological storage Basin lots with complexgeological structure and powerful water alternating are notsuitable CO2 geological storage candidate prospective areasdue to the high degree of hydrogeology and strong ground-water activities

Peak Ground Acceleration The GB 18306-2001 ldquoThe PeakGround Acceleration Zoning in Chinardquo shows the Chineseseismic zonation map its technical elements and user provi-sions It also applies to the CO2 geological storage construc-tion project The greater the peak ground acceleration is themore unfavorable it is for CO2 geological storage In generalthe peak ground acceleration should be less than 040 gBesides active faults are not only CO2 leakage pathways butalso cause damage to the strata continuity resulting in CO2

6 Geofluids

01 50 100 150 200 250 300 350

100

200

300

400

500

Number of basins

Stor

age p

oten

tial (

km2)

Figure 1 The statistical profile of CO2 geological storage potential per square kilometer of 390 onshore basins in China

leakage through the caprock According to the GB 17741-2005ldquoProject site seismic safety evaluationrdquo [33] the identificationof the capable fault has to be made within a 5 km range of thefirst class venues and epitaxy For seismic safety evaluationthe near-field region should be extended to a radius of 25 kmrange Therefore areas within 25 km of the active faults areinappropriate as the candidate prospective areas

Development Degree of Fractures CO2 could leak by tectonicpathways including faults fractures and ground fissures (eg[28 34ndash36]) Due to the complexity of geological structureand faults development in the Sichuan Basin the qualitativeassessment is based on the faults development and theexisting seismic data The more complex the fault systemis the more unfavorable it is for CO2 geological storage Inaddition there have been more frequent seismic activities inthe Sichuan Basin in recent years

(4) Storage Potential per Unit Area Guo (2014) evaluated thenational scale potential of CO2 geological storage in deepsaline aquifers of 390 onshore basins in China supported byChina Geological Survey As shown in Figure 1 the potentialof CO2 geological storage in deep saline aquifers in most ofthe sedimentary basins is 50 times 104ndash100 times 104 t generally anda small part of the basins are less than 10 times 104 t or more than100 times 104 t3 Candidate Prospective Areas for CO2Geological Utilization and Storage

The fine forming conditions of the reservoir mediums foroil gas and CBM make them possible that the existing oiland gas fields under production are the mesoscale candidateprospective areas or target areas in the short future Becauseof no official basin-scale data available the CO2 storagepotential of other CO2 geological utilization technologies isnot discussed further in this paper

31 Geology

311 Geostructure As shown in Figure 2 [37] the currentgeostructure of the Sichuan Basin consists of the Southeast

Table 7 Proven OGIP of 27 natural gas fields in the Sichuan Basin

Gas fields OGIP108m3

Puguang 405079Guangrsquoan 135558Hecuan 118706Datianchi 106755Xinchang 84302Luojiazhai 79736Moxi 70231Wolonghe 40886Weiyuan 40861Tieshanpo 37397Dukouhe 359Bajiaochang 35107Luodai 32383Qiongxi 32325Qilibei 28221Baimamiao 26872Dachigan 25871Gaofengchang 22726Qilixia 22548Hebaochang 22212Tieshan 18782Zhongba 1863Majing 17558Xindu 17532Chongxi 13635Fuchengzhai 1033Jiannan 10025

Sichuan fold belt Central Sichuan low uplift and NorthwestSichuan depression

312 Stratigraphy The Sichuan Basin sedimentary strata arecomplete with a total thickness of 6000ndash12000m Only thePermian and the younger strata are considered in this paperas follows from old to new

Geofluids 7

III1

III1

III2

Southeast Sichuan fold belt

Central Sichuan low uplift

Northwest Sichuan depression

Longmen Mountai

n fault z

one

Long

quan

Mou

ntain

faul

t zon

e

Huayin Mountain

fault z

one

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Tectonic units

First-order tectonic units

Second-order tectonic units

0 50 100 (km)

Gas fields

Oil fields

Faults

II1

II2

I2

I1

AZhongbaGas Field

Huaying MountainZhangjiachang

Gas FieldDachiganjing

Gas Field

FangdoushanMountain

B

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

WolongheGas Field

300∘ang

Figure 2 Sichuan Basin geological structure unit zoning map There are three first-order tectonic units in the Sichuan Basin that is theSoutheast Sichuan fold belt the Central Sichuan low uplift and the Northwest Sichuan depression The Southeast Sichuan fold belt consistsof the high steep fold belt in Eastern Sichuan (I1) and the low steep bottom fold belt in Southern Sichuan (I2) the Central Sichuan low upliftis composed of the flat fold belt in Central Sichuan (II1) and the low steep fold belt in Southwestern Sichuan (II2) the Northwest Sichuandepression consists of the low-lying fold belt in Northern Sichuan (III1) and the low steep fold belt in Western Sichuan (III2)

(1) The Permian Liangshan group (P1l) Qixia group(P2q) Maokou group (P2m) Longtan group (P3l)and Changxing group (P3c)

(2) The Triassic Feixianguan group (T1f ) Jialing Group(T1j) Leikoupo group (T2l) Tianjingshan group(T2t) Marsquoantang group (T3m) Xiaotangzi group(T3t) and Xujiahe group

(3) The Jurassic Ziliujing group (J1z) Qianfoya group(J2q) Shaximiao group (J2s) Suining group (J3s) andPenglaizhen group (J3p)

(4) The Cretaceous (K) and the Quaternary (Q)

313 Hydrodynamic Condition The Sichuan Basin is essen-tially an artesian basin dominated by Permian and Triassic

8 Geofluids

Chengdu

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Highly confined aquifers

Confined aquifers

Semiconfined aquifers

Open aquifers

Groundwater flow direction

First-order tectonic units

Second-order tectonic units

0 50 100(km)

I

I

II

II

II

II

II

II

III

III

III

IIIIII

III

IV

IV

IV

Leshan

Figure 3 Hydrodynamic conditions in the Sichuan Basin The groundwater activities are very strong in the peripheral target exposure areaIn contrast the groundwater activities inside the basin are relatively weak with better hydrogeological confinement On the edge of themountain around the Sichuan Basin and the eastern fold belt experiencing infiltration of fresh water due to the complex structure and strongwater alternating

strata The upper Jurassic and Cretaceous formations aremostly a large set of terrestrial clastic sedimentary rocks withred sandstones and mudstones throughout the basin Theyare extremely thick with poor permeability generally lowin moisture but exceedingly uneven which could be goodcaprocks for the reservoirs below them The lower upperTriassic Xujiahe consists of sandstones and shale and thesandstone may be good aquifers for CO2 geological storagedue to its huge thickness The lower and middle Triassicand Permian carbonate rocks are the main saline aquifersin which Triassic carbonate rocks often form alternate layerswith evaporites Therefore an aqueous rock series based onmany stacked white aquifers is formed in the Sichuan Basin(Figure 3)

314 Geological Safety There are many late Quaternaryactive faults on the boundary of the Sichuan Basin forexample the Longmenshan fault zone in NorthwesternSichuan has experienced more intense activity in recentyears It is the induced fracture of the ldquo512rdquo Wenchuan 80earthquake The Lushan 70 earthquake on April 20 2013 is

another devastating earthquake that followed the Wenchuan80 earthquake nearly five years later It is also closely linkedwith the Longmenshan fault belt

However the crust in the Central and Eastern SichuanBasin is more stable Historical earthquakes with magnitudeabove 6 mainly took place in Western Sichuan and South-western Sichuan Basin And the peak ground accelerationzoning according to the GB 18306-2001 ldquoThe Peak GroundAcceleration Zoning in Chinardquo is shown in Figure 4

32 Oil and Gas Fields The Sichuan Basin has abundantnatural gas resources mainly in Eastern Sichuan but arelatively small amount of oil resources The petroleumgeological reserves in the Sichuan Basin amount to 438 times108 t and only 075 times 108 t of proven OOIP in Central andNorthern Sichuan flat structure area [38]

By the end of 2008 theMinistry of Land and Resources ofChina (MLR) announced 125 gas fields in the Sichuan Basin(Figure 1) and the total amount of proven OGIP is 1722502times 108m3 Among them there are 27 medium to large-sizedconfirmed gas fields with OGIP exceeding 100 times 108m3 of

Geofluids 9

gt015 g

gt015

g

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Seismic peak ground acceleration First-order tectonic units

Second-order tectonic unitsHistorical earthquakes (M 6ndash69)

010 gndash015g

lt005 g

lt005 g

lt005 g

lt005 g

gndash010g005

0 50 100(km)

Figure 4 Seismic peak ground acceleration and large historical earthquakes in the Sichuan Basin The peak ground acceleration is less than010 g in most parts of the Sichuan Basin Only in the western margin of the Sichuan Basin the peak ground acceleration is larger than 015 g

which the total natural gas reserves are 1509268 times 108m3accounting for 876 of the total proven OGIP in the basin(Table 7)

33 Unmineable Coal Seams The CBM geological reservesin the Sichuan Basin amount to 347140 times 108m3 in Sichuanprovince and Chongqing city 508457 times 108m3 in SouthernSichuan province and Northern Guizhou province respec-tively from 1000 to 2000meters depth [39] Among these thecoalfields in Southern Sichuan province are the most abun-dant accounting for 82 of the provincersquos total resources

34 Deep Saline Aquifers Comparedwith oil fields gas fieldsand unmineable coal seams the analysis of geological condi-tions for saline aquifers CO2 geological storage is muchmorecomplex The CO2 geological storage candidate prospectivearea for deep saline aquifers CO2 storage was selected fromthe map projection on the ground of all potential under-ground CO2 reservoirs In addition the hydrodynamic andgeological safety conditions must be studied to delineate thecandidate prospective areas

341 Candidate Prospective Area Delineation Standards Asmentioned above this report presents the delineation stan-dards of the CO2 geological storage candidate prospective

Table 8 Veto over key factors of CO2 geological storage candidateprospective areas delineation

Key factors VetoReservoir conditions

Layer thickness lt10mPorosity lt5Permeability lt1mD

Hydrogeological conditionsFormation water salinity lt3 gLGroundwater hydrodynamic condition Groundwater zone

Geological safety conditionsActive faults lt25 kmPeak ground acceleration ge040 g

areas shown in Table 8 Further potential and suitabilityassessments can be carried out for target area selection

342 Vertical Reservoir Cap Combination and CandidateProspective Areas Distribution The reservoirs for deep salineaquifer CO2 storage consist of the Permian the lower Triassiccarbonates and upper Triassic and Jurassic clastic reservoirs(Figure 5)The reservoir space includes carbonate karst poresand cracks and clastic pores and cracks Overall all reservoirs

10 Geofluids

Geochronology

Series Formation

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Penglaizhen

Suining

Shaximiao

Qianfoya

Ziliujing

Six

Xiaotangzi

Marsquoantang

Tianjingshan

Leikoupo

Changxing

Longtan

Maokou

Qixia

LiangshanCarbon-iferous

Permian

Upper

Stata

Middle

Lower

Upper

Upper

Middle

Middle

Lower

Lower

Five

Four

Three

Two

One

Four

Three

Two

One

Five

Four

Three

Two

One

Litho-histogram

D

depr

essio

nrift

Sandstone

Mudstone

Mud sandstone

Limestone

Dolomite

Reservoir

Caprock

Thick-ness(m)

Poro-sity()

Perme-ability(mD)

Coverage

Local

Regional

Regional

Regional

1244

5Local

Average

5Local

AverageLocal

10 5Local

10 5Local

Porefracture

Reservoirspace

fracture

Porefracture

Porefracture

Dissolved porefracture

Fracture-cave

Fracture-cave

Porefracture

525Average

605AverageLocal

Average

Dissolved pore

Dissolved pore

Rese

rvoi

r

Capr

ock

Tect

onic

mov

emen

tBa

sinev

olut

ion

Mid

dle Y

ansh

an

Fore

land

Late

Indo

sinia

n

Intr

acra

toni

c

ongw

u

Pore

001ndash10

gt1

gt200

gt1

gt1gt6

gt7

gt1

gt1

gt8gt10

gt1

gt1

gt1725

4ndash10

6ndash80

25ndash70

25ndash30

100ndash200

100ndash200

0ndash300

Jialin

gjia

ngFe

ixia

ngua

nXu

jiahe

Figure 5 CO2 geological storage vertical reservoir cap combination in the Sichuan Basin There are nine sets of reservoirs in the SichuanBasin and the section four of Xujiahe group is the primary reservoir with large thickness and area which almost cover the whole basin

Geofluids 11

Table 9 Storage potential of CO2 geological storage in depleted oil fields

Tectonic unit OOIP108 t Oil density(kgm3) 119861 (mdash) Reservoir

pressureMpaOil

temperature∘C120588CO2

(kgm3)119864oil 119866CO2

108 t

Central Sichuan flatstructure area 058 850 118 2126 6442 71263 075 057

Northern Sichuan flatstructure area 017 850 118 2126 6442 71263 075 017

Table 10 CO2-EOR geological storage potential in the Sichuan Basin

Tectonic unit API EXTRA () 119875LCO2() 119875HCO2

() 119864oil 119866CO2-EOR108 t

Central Sichuan flatstructure area 3497 1046 33 66 075 016

Northern Sichuan flatstructure area 3497 1046 33 66 075 005

in the Sichuan Basin have poor physical properties withultra-low porosity and low permeability Comparing withthe natural gas fields in the Sichuan Basin these reservoirsfor CO2 storage have better caprock conditions too Forexample the extensive deposits of gypsum rocks in theLeikoupo phase and the widely developed dark mudstone inthe Lower Jurassic can provide good sealing conditions forthe underlying reservoirs

(1) The Permian The reef flat facies on the top of Qixiagroup form a good reservoir through dolomitization withfavorable reservoir conditions (P2q) [40] Part of them formthe natural gas reservoirs with a thickness of approximately10m Similar to the Qixia group the Maokou group (P2m)is a fracture-cave type of reservoir Changxing group (P3c)reservoirs are pore type and fracture-pore type The porosityis generally 203ndash1585 with an average value of 525 thepermeability is less than 1000mD with an average value of605mD The reservoir thickness is large with a monolayerthickness of 05ndash5m and a single well cumulative thicknessof 25ndash70m [41]

(2) The Triassic The Feixianguan group (T1f ) is similar tothe Changxing groupThe quality and distribution of the reefbeach reservoir are mainly controlled by sedimentary faciesand diagenesis The evaporative platform oolitic dolomitereservoir is mainly distributed in Northeast Sichuan witha monolayer thickness of 15ndash15m and total thickness of20ndash50m The porosity ranges from 2 to 268 on theaverage of 829 and the permeability is less than 1160mDwith an average value of 5973mD The porosity of the openplatform edge oolitic dolomite reservoir is 205ndash2262 onthe average of 842 and the permeability is less than 410mDwith an average value of 1725mD The reservoir monolayerthickness is generally 05ndash6m and the total thickness is10ndash45m typically

The favorable Jialingjiang reservoir facies are the platforminterior shoal and the platform margin shoal facies Forexample section five of Jialingjiang reservoirs consists oflimestone and dolomite with a thickness of 25ndash30m ofwhich approximately 60 is the porosity layer and the

average of the porosity is 5 with the highest value reaching18

The sandstone aquifers in section two section four andsection six of Xujiahe formation could be reservoirs for CO2geological storage composed of residual intergranular poreintergranular dissolved pore and fracture The sand ratioof the sandstones is greater than 70 in 80 generally Inaddition the porosity of section four is higher than sectiontwo and section six usually between 5ndash10 while theporosity of sandstones in section two and section is less than7 generally

Figure 6 shows the candidate prospective areas in theSichuan Basin in the Sichuan Basin for deep saline aquiferCO2 storage based on geology study

4 Results

41 Potential

411 Depleted Oil Fields CO2 Storage and CO2-EOR Theprimary CO2-EOR prospective areas in the Sichuan Basinare located in the flat tectonic area in Central and NorthernSichuan Basin As shown in Tables 9 and 10 the CO2geological storage potential of storage in depleted oil fieldsis only 074 times 108 t while the storage potential is about 021 times108 t by using CO2-EOR technology

412 Depleted Gas Fields CO2 Storage and CO2-EGR TheCO2 geological storage potential of depleted gas fields is 5373times 108 t By using CO2-EGR technology the Sichuan Basin gasfields could achieve CO2 geological storage of 3385 times 108 tAmong that 27 large and medium gas fields have the greatestpotential with the possibility of achieving a CO2 geologicalstorage capacity of 4239 times 108 t in depleted gas fields whilethe storage potential is about 2670 times 108 t by using CO2-EGRtechnology

413 Unmineable Coal Seams CO2 Storage and CO2-ECBMThe Sichuan Basin has abundant coal bedmethane resourcesAs shown in Table 11 the total CO2 geological storage

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

4 Geofluids

Table6Indexsyste

mforg

eologicalsuitabilityassessmenttoselectsuitabletargetsford

eepsalin

eaqu

iferC

O2sto

rage

Levelone

index

Weight

Leveltwoindex

Weight

Levelthree

index

Weight

Goo

dGeneral

Poor

Keyveto

factor

Reservoir

cond

ition

sand

storage

potential

050

Characteris

ticof

theb

estreservoir

060

Litholog

y007

Clastic

Mixof

clasticand

carbon

ate

Carbo

nate

Sing

lelayer

thickn

essh

m011

ge8030lehlt8

010lehlt3

0lt10

Sedimentary

facies

036

Riverdelta

Turbidityallu

vial

fan

Beachbarreef

Averagep

orosity

120593020

ge1510le120593lt15

5le120593lt10

lt5Av

erage

perm

eability119896m

D027

ge5010leklt5

01le

klt10

lt1Storagep

otentia

l040

Storagep

otentia

lperu

nitareaG

(104

tkm2)

100

ge100

10leGlt10

0lt10

Geologicalsafety

050

Characteris

ticof

them

aincaprock

062

Litholog

y030

Evaporites

Argillite

Shalea

nddense

limestone

Thickn

essh

m053

ge100

50lehlt10

010lehlt5

0lt10

Depth

Dm

011

1000leDle2

700

lt1000

gt2700

Bufferc

aprock

abovethe

main

caprock

006

Multip

lesets

Sing

leset

Non

e

Hydrodynamic

cond

ition

s024

Hydrodynamic

cond

ition

s10

0Groun

dwater

high

-con

tainment

area

Groun

dwater

containm

entarea

Groun

dwater

semicon

tainment

area

Groun

dwater

open

area

Seism

icactiv

ity014

Peak

grou

ndacceleratio

n050

lt005

g005

g010g

015g020

g030

gge0

40g

Develo

pment

degree

offractures

050

Simple

Mod

erate

Com

plex

With

in25

kmof

activ

efaults

Geofluids 5

Then GIS spatial analysis and evaluation are carried outusing formula (9)

119875 = 119899sum119894=1

119875119894119860 119894 (119894 = 1 2 3 119899) (9)

Here P is suitability scores of unit for CO2 geological storage119899 is the total number of evaluation factors 119875119894 is given point ofthe factor 119894 119860 119894 is index weight of the factor 119894

Single metric suitability rating is as follows ldquogoodrdquo 9points ldquogeneralrdquo 5 points and ldquopoorrdquo 1 pointThe evaluationresult suitability rating is as follows ldquohighly suitablerdquo valuerange 7 le P le 9 ldquosuitablerdquo 5 le P lt 7 ldquoless suitablerdquo 3 le P lt 5and ldquounsuitablerdquo 1 le P lt 3222 Index System for Geological Suitability Assessment Asshown in Table 6 the index system for geological suitabilityhas three hierarchies The index weights at all levels aredetermined using the Analytic Hierarchy Process (AHP) [2021]

The assessment indexes are described detailed in thefollowing

(1) Characteristic of the Best Reservoir

Depth Only if the theoretical storage depth is more than 800meters can CO2 enter the supercritical state normally lowthan 3500 meters

Lithology According to the existing commercial-scale CO2geological storage projects (eg [22ndash24]) reservoir charac-teristics of oil and gas fields inChina [25] and the engineeringverification by the Shenhua CCS demonstration project inthe Ordos Basin in China [26] clastic reservoirs are generallybetter than carbonate reservoirs

Single Layer Thickness Because of terrestrial sedimentaryfacies in most formations in onshore basins of China it isdifficult to find the large thick aquifers forCO2 storage similaras Sleipner project in Norway The minimum single layerthickness of reservoirs recommended in this paper is 10m

Sedimentary Facies Most Cenozoic sedimentary basins inChina are terrestrial sedimentary formations The main partof the reservoir is the deltaic sand body followed by theturbidite sand and alluvial fan glutinite body and finally thesand beach dams and a small amount of reef

Porosity and Permeability Low porosity and permeability is aspecial feature in terrestrial sedimentary oil and gas reservoirsand saline aquifers in China Generally for both the clasticand carbonate rock reservoirs the porosity should be greaterthan or equal to 5 and permeability should be greater thanor equal to 1mD (eg [27ndash30])

(2) Characteristic of the Main Caprock

Lithology The most common caprocks of oil and gas fieldsin China are argillite (mudstone and shale) and evapor-ites (gypsum and rock salt) followed by carbonate rocks

(marl argillaceous dolomite compact limestone and densedolomite) and frozen genesis caps Sometimes there are localchert layers seams dense volcanic rocks and intrusive rockcaps

ThicknessThere are certain relationships between cap thick-ness and the size and height of the reservoir With thecombination of existing cap thickness grading standards [30]and considerations of the differences between CO2 and oiland gas the reference criteria for grading the classificationof CO2 geological storage cap thickness can be specifiedThe minimum thickness of CO2 geological storage caprocksrecommended in this paper is 10m

Burial Depth The cap type is argillaceous rocks The diage-nesis has different effects on the performance of the caprockat different stage [31] When the burial depth of argillaceousrocks is less than 1000m the diagenetic degree is poor and thesealing mainly relies on the capillary pressure The porosityand permeability are good but with poor plasticity At theburial depth of 1000ndash2700m the diagenesis is enhancedmineral particles inside the argillaceous rock become morecompacted the porosity and permeability deteriorate theplasticity increases the capillary flow capacity declines seal-ing ability improves and there is abnormal sealing pressureWhen the burial depth is greater than 2700m it is equiv-alent to the tightly compacted stage of the Argillite Thediagenesis is boosted further the plasticity decreases andfragility increases with the increase in the abnormal pressuremicrocracks appear on the argillaceous rocks and capillarysealing ability deteriorates

The ldquoBuffer Caprdquo above the Main Caprock When the CO2breaks through the main cap the ldquobuffer caprdquo above the maincap has to provide a certain sealing capability to reduce orprevent the escape of CO2

(3) Geological Safety

Hydrodynamic Conditions Ye et al [32] divided the effectof hydrogeological conditions controlling coalbed methaneinto three categories hydraulic transport dissipation effecthydraulic seal effect and hydraulic block effect The moreclosed the hydrogeological conditions are themore favorablethey are for CO2 geological storage Basin lots with complexgeological structure and powerful water alternating are notsuitable CO2 geological storage candidate prospective areasdue to the high degree of hydrogeology and strong ground-water activities

Peak Ground Acceleration The GB 18306-2001 ldquoThe PeakGround Acceleration Zoning in Chinardquo shows the Chineseseismic zonation map its technical elements and user provi-sions It also applies to the CO2 geological storage construc-tion project The greater the peak ground acceleration is themore unfavorable it is for CO2 geological storage In generalthe peak ground acceleration should be less than 040 gBesides active faults are not only CO2 leakage pathways butalso cause damage to the strata continuity resulting in CO2

6 Geofluids

01 50 100 150 200 250 300 350

100

200

300

400

500

Number of basins

Stor

age p

oten

tial (

km2)

Figure 1 The statistical profile of CO2 geological storage potential per square kilometer of 390 onshore basins in China

leakage through the caprock According to the GB 17741-2005ldquoProject site seismic safety evaluationrdquo [33] the identificationof the capable fault has to be made within a 5 km range of thefirst class venues and epitaxy For seismic safety evaluationthe near-field region should be extended to a radius of 25 kmrange Therefore areas within 25 km of the active faults areinappropriate as the candidate prospective areas

Development Degree of Fractures CO2 could leak by tectonicpathways including faults fractures and ground fissures (eg[28 34ndash36]) Due to the complexity of geological structureand faults development in the Sichuan Basin the qualitativeassessment is based on the faults development and theexisting seismic data The more complex the fault systemis the more unfavorable it is for CO2 geological storage Inaddition there have been more frequent seismic activities inthe Sichuan Basin in recent years

(4) Storage Potential per Unit Area Guo (2014) evaluated thenational scale potential of CO2 geological storage in deepsaline aquifers of 390 onshore basins in China supported byChina Geological Survey As shown in Figure 1 the potentialof CO2 geological storage in deep saline aquifers in most ofthe sedimentary basins is 50 times 104ndash100 times 104 t generally anda small part of the basins are less than 10 times 104 t or more than100 times 104 t3 Candidate Prospective Areas for CO2Geological Utilization and Storage

The fine forming conditions of the reservoir mediums foroil gas and CBM make them possible that the existing oiland gas fields under production are the mesoscale candidateprospective areas or target areas in the short future Becauseof no official basin-scale data available the CO2 storagepotential of other CO2 geological utilization technologies isnot discussed further in this paper

31 Geology

311 Geostructure As shown in Figure 2 [37] the currentgeostructure of the Sichuan Basin consists of the Southeast

Table 7 Proven OGIP of 27 natural gas fields in the Sichuan Basin

Gas fields OGIP108m3

Puguang 405079Guangrsquoan 135558Hecuan 118706Datianchi 106755Xinchang 84302Luojiazhai 79736Moxi 70231Wolonghe 40886Weiyuan 40861Tieshanpo 37397Dukouhe 359Bajiaochang 35107Luodai 32383Qiongxi 32325Qilibei 28221Baimamiao 26872Dachigan 25871Gaofengchang 22726Qilixia 22548Hebaochang 22212Tieshan 18782Zhongba 1863Majing 17558Xindu 17532Chongxi 13635Fuchengzhai 1033Jiannan 10025

Sichuan fold belt Central Sichuan low uplift and NorthwestSichuan depression

312 Stratigraphy The Sichuan Basin sedimentary strata arecomplete with a total thickness of 6000ndash12000m Only thePermian and the younger strata are considered in this paperas follows from old to new

Geofluids 7

III1

III1

III2

Southeast Sichuan fold belt

Central Sichuan low uplift

Northwest Sichuan depression

Longmen Mountai

n fault z

one

Long

quan

Mou

ntain

faul

t zon

e

Huayin Mountain

fault z

one

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Tectonic units

First-order tectonic units

Second-order tectonic units

0 50 100 (km)

Gas fields

Oil fields

Faults

II1

II2

I2

I1

AZhongbaGas Field

Huaying MountainZhangjiachang

Gas FieldDachiganjing

Gas Field

FangdoushanMountain

B

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

WolongheGas Field

300∘ang

Figure 2 Sichuan Basin geological structure unit zoning map There are three first-order tectonic units in the Sichuan Basin that is theSoutheast Sichuan fold belt the Central Sichuan low uplift and the Northwest Sichuan depression The Southeast Sichuan fold belt consistsof the high steep fold belt in Eastern Sichuan (I1) and the low steep bottom fold belt in Southern Sichuan (I2) the Central Sichuan low upliftis composed of the flat fold belt in Central Sichuan (II1) and the low steep fold belt in Southwestern Sichuan (II2) the Northwest Sichuandepression consists of the low-lying fold belt in Northern Sichuan (III1) and the low steep fold belt in Western Sichuan (III2)

(1) The Permian Liangshan group (P1l) Qixia group(P2q) Maokou group (P2m) Longtan group (P3l)and Changxing group (P3c)

(2) The Triassic Feixianguan group (T1f ) Jialing Group(T1j) Leikoupo group (T2l) Tianjingshan group(T2t) Marsquoantang group (T3m) Xiaotangzi group(T3t) and Xujiahe group

(3) The Jurassic Ziliujing group (J1z) Qianfoya group(J2q) Shaximiao group (J2s) Suining group (J3s) andPenglaizhen group (J3p)

(4) The Cretaceous (K) and the Quaternary (Q)

313 Hydrodynamic Condition The Sichuan Basin is essen-tially an artesian basin dominated by Permian and Triassic

8 Geofluids

Chengdu

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Highly confined aquifers

Confined aquifers

Semiconfined aquifers

Open aquifers

Groundwater flow direction

First-order tectonic units

Second-order tectonic units

0 50 100(km)

I

I

II

II

II

II

II

II

III

III

III

IIIIII

III

IV

IV

IV

Leshan

Figure 3 Hydrodynamic conditions in the Sichuan Basin The groundwater activities are very strong in the peripheral target exposure areaIn contrast the groundwater activities inside the basin are relatively weak with better hydrogeological confinement On the edge of themountain around the Sichuan Basin and the eastern fold belt experiencing infiltration of fresh water due to the complex structure and strongwater alternating

strata The upper Jurassic and Cretaceous formations aremostly a large set of terrestrial clastic sedimentary rocks withred sandstones and mudstones throughout the basin Theyare extremely thick with poor permeability generally lowin moisture but exceedingly uneven which could be goodcaprocks for the reservoirs below them The lower upperTriassic Xujiahe consists of sandstones and shale and thesandstone may be good aquifers for CO2 geological storagedue to its huge thickness The lower and middle Triassicand Permian carbonate rocks are the main saline aquifersin which Triassic carbonate rocks often form alternate layerswith evaporites Therefore an aqueous rock series based onmany stacked white aquifers is formed in the Sichuan Basin(Figure 3)

314 Geological Safety There are many late Quaternaryactive faults on the boundary of the Sichuan Basin forexample the Longmenshan fault zone in NorthwesternSichuan has experienced more intense activity in recentyears It is the induced fracture of the ldquo512rdquo Wenchuan 80earthquake The Lushan 70 earthquake on April 20 2013 is

another devastating earthquake that followed the Wenchuan80 earthquake nearly five years later It is also closely linkedwith the Longmenshan fault belt

However the crust in the Central and Eastern SichuanBasin is more stable Historical earthquakes with magnitudeabove 6 mainly took place in Western Sichuan and South-western Sichuan Basin And the peak ground accelerationzoning according to the GB 18306-2001 ldquoThe Peak GroundAcceleration Zoning in Chinardquo is shown in Figure 4

32 Oil and Gas Fields The Sichuan Basin has abundantnatural gas resources mainly in Eastern Sichuan but arelatively small amount of oil resources The petroleumgeological reserves in the Sichuan Basin amount to 438 times108 t and only 075 times 108 t of proven OOIP in Central andNorthern Sichuan flat structure area [38]

By the end of 2008 theMinistry of Land and Resources ofChina (MLR) announced 125 gas fields in the Sichuan Basin(Figure 1) and the total amount of proven OGIP is 1722502times 108m3 Among them there are 27 medium to large-sizedconfirmed gas fields with OGIP exceeding 100 times 108m3 of

Geofluids 9

gt015 g

gt015

g

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Seismic peak ground acceleration First-order tectonic units

Second-order tectonic unitsHistorical earthquakes (M 6ndash69)

010 gndash015g

lt005 g

lt005 g

lt005 g

lt005 g

gndash010g005

0 50 100(km)

Figure 4 Seismic peak ground acceleration and large historical earthquakes in the Sichuan Basin The peak ground acceleration is less than010 g in most parts of the Sichuan Basin Only in the western margin of the Sichuan Basin the peak ground acceleration is larger than 015 g

which the total natural gas reserves are 1509268 times 108m3accounting for 876 of the total proven OGIP in the basin(Table 7)

33 Unmineable Coal Seams The CBM geological reservesin the Sichuan Basin amount to 347140 times 108m3 in Sichuanprovince and Chongqing city 508457 times 108m3 in SouthernSichuan province and Northern Guizhou province respec-tively from 1000 to 2000meters depth [39] Among these thecoalfields in Southern Sichuan province are the most abun-dant accounting for 82 of the provincersquos total resources

34 Deep Saline Aquifers Comparedwith oil fields gas fieldsand unmineable coal seams the analysis of geological condi-tions for saline aquifers CO2 geological storage is muchmorecomplex The CO2 geological storage candidate prospectivearea for deep saline aquifers CO2 storage was selected fromthe map projection on the ground of all potential under-ground CO2 reservoirs In addition the hydrodynamic andgeological safety conditions must be studied to delineate thecandidate prospective areas

341 Candidate Prospective Area Delineation Standards Asmentioned above this report presents the delineation stan-dards of the CO2 geological storage candidate prospective

Table 8 Veto over key factors of CO2 geological storage candidateprospective areas delineation

Key factors VetoReservoir conditions

Layer thickness lt10mPorosity lt5Permeability lt1mD

Hydrogeological conditionsFormation water salinity lt3 gLGroundwater hydrodynamic condition Groundwater zone

Geological safety conditionsActive faults lt25 kmPeak ground acceleration ge040 g

areas shown in Table 8 Further potential and suitabilityassessments can be carried out for target area selection

342 Vertical Reservoir Cap Combination and CandidateProspective Areas Distribution The reservoirs for deep salineaquifer CO2 storage consist of the Permian the lower Triassiccarbonates and upper Triassic and Jurassic clastic reservoirs(Figure 5)The reservoir space includes carbonate karst poresand cracks and clastic pores and cracks Overall all reservoirs

10 Geofluids

Geochronology

Series Formation

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Penglaizhen

Suining

Shaximiao

Qianfoya

Ziliujing

Six

Xiaotangzi

Marsquoantang

Tianjingshan

Leikoupo

Changxing

Longtan

Maokou

Qixia

LiangshanCarbon-iferous

Permian

Upper

Stata

Middle

Lower

Upper

Upper

Middle

Middle

Lower

Lower

Five

Four

Three

Two

One

Four

Three

Two

One

Five

Four

Three

Two

One

Litho-histogram

D

depr

essio

nrift

Sandstone

Mudstone

Mud sandstone

Limestone

Dolomite

Reservoir

Caprock

Thick-ness(m)

Poro-sity()

Perme-ability(mD)

Coverage

Local

Regional

Regional

Regional

1244

5Local

Average

5Local

AverageLocal

10 5Local

10 5Local

Porefracture

Reservoirspace

fracture

Porefracture

Porefracture

Dissolved porefracture

Fracture-cave

Fracture-cave

Porefracture

525Average

605AverageLocal

Average

Dissolved pore

Dissolved pore

Rese

rvoi

r

Capr

ock

Tect

onic

mov

emen

tBa

sinev

olut

ion

Mid

dle Y

ansh

an

Fore

land

Late

Indo

sinia

n

Intr

acra

toni

c

ongw

u

Pore

001ndash10

gt1

gt200

gt1

gt1gt6

gt7

gt1

gt1

gt8gt10

gt1

gt1

gt1725

4ndash10

6ndash80

25ndash70

25ndash30

100ndash200

100ndash200

0ndash300

Jialin

gjia

ngFe

ixia

ngua

nXu

jiahe

Figure 5 CO2 geological storage vertical reservoir cap combination in the Sichuan Basin There are nine sets of reservoirs in the SichuanBasin and the section four of Xujiahe group is the primary reservoir with large thickness and area which almost cover the whole basin

Geofluids 11

Table 9 Storage potential of CO2 geological storage in depleted oil fields

Tectonic unit OOIP108 t Oil density(kgm3) 119861 (mdash) Reservoir

pressureMpaOil

temperature∘C120588CO2

(kgm3)119864oil 119866CO2

108 t

Central Sichuan flatstructure area 058 850 118 2126 6442 71263 075 057

Northern Sichuan flatstructure area 017 850 118 2126 6442 71263 075 017

Table 10 CO2-EOR geological storage potential in the Sichuan Basin

Tectonic unit API EXTRA () 119875LCO2() 119875HCO2

() 119864oil 119866CO2-EOR108 t

Central Sichuan flatstructure area 3497 1046 33 66 075 016

Northern Sichuan flatstructure area 3497 1046 33 66 075 005

in the Sichuan Basin have poor physical properties withultra-low porosity and low permeability Comparing withthe natural gas fields in the Sichuan Basin these reservoirsfor CO2 storage have better caprock conditions too Forexample the extensive deposits of gypsum rocks in theLeikoupo phase and the widely developed dark mudstone inthe Lower Jurassic can provide good sealing conditions forthe underlying reservoirs

(1) The Permian The reef flat facies on the top of Qixiagroup form a good reservoir through dolomitization withfavorable reservoir conditions (P2q) [40] Part of them formthe natural gas reservoirs with a thickness of approximately10m Similar to the Qixia group the Maokou group (P2m)is a fracture-cave type of reservoir Changxing group (P3c)reservoirs are pore type and fracture-pore type The porosityis generally 203ndash1585 with an average value of 525 thepermeability is less than 1000mD with an average value of605mD The reservoir thickness is large with a monolayerthickness of 05ndash5m and a single well cumulative thicknessof 25ndash70m [41]

(2) The Triassic The Feixianguan group (T1f ) is similar tothe Changxing groupThe quality and distribution of the reefbeach reservoir are mainly controlled by sedimentary faciesand diagenesis The evaporative platform oolitic dolomitereservoir is mainly distributed in Northeast Sichuan witha monolayer thickness of 15ndash15m and total thickness of20ndash50m The porosity ranges from 2 to 268 on theaverage of 829 and the permeability is less than 1160mDwith an average value of 5973mD The porosity of the openplatform edge oolitic dolomite reservoir is 205ndash2262 onthe average of 842 and the permeability is less than 410mDwith an average value of 1725mD The reservoir monolayerthickness is generally 05ndash6m and the total thickness is10ndash45m typically

The favorable Jialingjiang reservoir facies are the platforminterior shoal and the platform margin shoal facies Forexample section five of Jialingjiang reservoirs consists oflimestone and dolomite with a thickness of 25ndash30m ofwhich approximately 60 is the porosity layer and the

average of the porosity is 5 with the highest value reaching18

The sandstone aquifers in section two section four andsection six of Xujiahe formation could be reservoirs for CO2geological storage composed of residual intergranular poreintergranular dissolved pore and fracture The sand ratioof the sandstones is greater than 70 in 80 generally Inaddition the porosity of section four is higher than sectiontwo and section six usually between 5ndash10 while theporosity of sandstones in section two and section is less than7 generally

Figure 6 shows the candidate prospective areas in theSichuan Basin in the Sichuan Basin for deep saline aquiferCO2 storage based on geology study

4 Results

41 Potential

411 Depleted Oil Fields CO2 Storage and CO2-EOR Theprimary CO2-EOR prospective areas in the Sichuan Basinare located in the flat tectonic area in Central and NorthernSichuan Basin As shown in Tables 9 and 10 the CO2geological storage potential of storage in depleted oil fieldsis only 074 times 108 t while the storage potential is about 021 times108 t by using CO2-EOR technology

412 Depleted Gas Fields CO2 Storage and CO2-EGR TheCO2 geological storage potential of depleted gas fields is 5373times 108 t By using CO2-EGR technology the Sichuan Basin gasfields could achieve CO2 geological storage of 3385 times 108 tAmong that 27 large and medium gas fields have the greatestpotential with the possibility of achieving a CO2 geologicalstorage capacity of 4239 times 108 t in depleted gas fields whilethe storage potential is about 2670 times 108 t by using CO2-EGRtechnology

413 Unmineable Coal Seams CO2 Storage and CO2-ECBMThe Sichuan Basin has abundant coal bedmethane resourcesAs shown in Table 11 the total CO2 geological storage

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

Geofluids 5

Then GIS spatial analysis and evaluation are carried outusing formula (9)

119875 = 119899sum119894=1

119875119894119860 119894 (119894 = 1 2 3 119899) (9)

Here P is suitability scores of unit for CO2 geological storage119899 is the total number of evaluation factors 119875119894 is given point ofthe factor 119894 119860 119894 is index weight of the factor 119894

Single metric suitability rating is as follows ldquogoodrdquo 9points ldquogeneralrdquo 5 points and ldquopoorrdquo 1 pointThe evaluationresult suitability rating is as follows ldquohighly suitablerdquo valuerange 7 le P le 9 ldquosuitablerdquo 5 le P lt 7 ldquoless suitablerdquo 3 le P lt 5and ldquounsuitablerdquo 1 le P lt 3222 Index System for Geological Suitability Assessment Asshown in Table 6 the index system for geological suitabilityhas three hierarchies The index weights at all levels aredetermined using the Analytic Hierarchy Process (AHP) [2021]

The assessment indexes are described detailed in thefollowing

(1) Characteristic of the Best Reservoir

Depth Only if the theoretical storage depth is more than 800meters can CO2 enter the supercritical state normally lowthan 3500 meters

Lithology According to the existing commercial-scale CO2geological storage projects (eg [22ndash24]) reservoir charac-teristics of oil and gas fields inChina [25] and the engineeringverification by the Shenhua CCS demonstration project inthe Ordos Basin in China [26] clastic reservoirs are generallybetter than carbonate reservoirs

Single Layer Thickness Because of terrestrial sedimentaryfacies in most formations in onshore basins of China it isdifficult to find the large thick aquifers forCO2 storage similaras Sleipner project in Norway The minimum single layerthickness of reservoirs recommended in this paper is 10m

Sedimentary Facies Most Cenozoic sedimentary basins inChina are terrestrial sedimentary formations The main partof the reservoir is the deltaic sand body followed by theturbidite sand and alluvial fan glutinite body and finally thesand beach dams and a small amount of reef

Porosity and Permeability Low porosity and permeability is aspecial feature in terrestrial sedimentary oil and gas reservoirsand saline aquifers in China Generally for both the clasticand carbonate rock reservoirs the porosity should be greaterthan or equal to 5 and permeability should be greater thanor equal to 1mD (eg [27ndash30])

(2) Characteristic of the Main Caprock

Lithology The most common caprocks of oil and gas fieldsin China are argillite (mudstone and shale) and evapor-ites (gypsum and rock salt) followed by carbonate rocks

(marl argillaceous dolomite compact limestone and densedolomite) and frozen genesis caps Sometimes there are localchert layers seams dense volcanic rocks and intrusive rockcaps

ThicknessThere are certain relationships between cap thick-ness and the size and height of the reservoir With thecombination of existing cap thickness grading standards [30]and considerations of the differences between CO2 and oiland gas the reference criteria for grading the classificationof CO2 geological storage cap thickness can be specifiedThe minimum thickness of CO2 geological storage caprocksrecommended in this paper is 10m

Burial Depth The cap type is argillaceous rocks The diage-nesis has different effects on the performance of the caprockat different stage [31] When the burial depth of argillaceousrocks is less than 1000m the diagenetic degree is poor and thesealing mainly relies on the capillary pressure The porosityand permeability are good but with poor plasticity At theburial depth of 1000ndash2700m the diagenesis is enhancedmineral particles inside the argillaceous rock become morecompacted the porosity and permeability deteriorate theplasticity increases the capillary flow capacity declines seal-ing ability improves and there is abnormal sealing pressureWhen the burial depth is greater than 2700m it is equiv-alent to the tightly compacted stage of the Argillite Thediagenesis is boosted further the plasticity decreases andfragility increases with the increase in the abnormal pressuremicrocracks appear on the argillaceous rocks and capillarysealing ability deteriorates

The ldquoBuffer Caprdquo above the Main Caprock When the CO2breaks through the main cap the ldquobuffer caprdquo above the maincap has to provide a certain sealing capability to reduce orprevent the escape of CO2

(3) Geological Safety

Hydrodynamic Conditions Ye et al [32] divided the effectof hydrogeological conditions controlling coalbed methaneinto three categories hydraulic transport dissipation effecthydraulic seal effect and hydraulic block effect The moreclosed the hydrogeological conditions are themore favorablethey are for CO2 geological storage Basin lots with complexgeological structure and powerful water alternating are notsuitable CO2 geological storage candidate prospective areasdue to the high degree of hydrogeology and strong ground-water activities

Peak Ground Acceleration The GB 18306-2001 ldquoThe PeakGround Acceleration Zoning in Chinardquo shows the Chineseseismic zonation map its technical elements and user provi-sions It also applies to the CO2 geological storage construc-tion project The greater the peak ground acceleration is themore unfavorable it is for CO2 geological storage In generalthe peak ground acceleration should be less than 040 gBesides active faults are not only CO2 leakage pathways butalso cause damage to the strata continuity resulting in CO2

6 Geofluids

01 50 100 150 200 250 300 350

100

200

300

400

500

Number of basins

Stor

age p

oten

tial (

km2)

Figure 1 The statistical profile of CO2 geological storage potential per square kilometer of 390 onshore basins in China

leakage through the caprock According to the GB 17741-2005ldquoProject site seismic safety evaluationrdquo [33] the identificationof the capable fault has to be made within a 5 km range of thefirst class venues and epitaxy For seismic safety evaluationthe near-field region should be extended to a radius of 25 kmrange Therefore areas within 25 km of the active faults areinappropriate as the candidate prospective areas

Development Degree of Fractures CO2 could leak by tectonicpathways including faults fractures and ground fissures (eg[28 34ndash36]) Due to the complexity of geological structureand faults development in the Sichuan Basin the qualitativeassessment is based on the faults development and theexisting seismic data The more complex the fault systemis the more unfavorable it is for CO2 geological storage Inaddition there have been more frequent seismic activities inthe Sichuan Basin in recent years

(4) Storage Potential per Unit Area Guo (2014) evaluated thenational scale potential of CO2 geological storage in deepsaline aquifers of 390 onshore basins in China supported byChina Geological Survey As shown in Figure 1 the potentialof CO2 geological storage in deep saline aquifers in most ofthe sedimentary basins is 50 times 104ndash100 times 104 t generally anda small part of the basins are less than 10 times 104 t or more than100 times 104 t3 Candidate Prospective Areas for CO2Geological Utilization and Storage

The fine forming conditions of the reservoir mediums foroil gas and CBM make them possible that the existing oiland gas fields under production are the mesoscale candidateprospective areas or target areas in the short future Becauseof no official basin-scale data available the CO2 storagepotential of other CO2 geological utilization technologies isnot discussed further in this paper

31 Geology

311 Geostructure As shown in Figure 2 [37] the currentgeostructure of the Sichuan Basin consists of the Southeast

Table 7 Proven OGIP of 27 natural gas fields in the Sichuan Basin

Gas fields OGIP108m3

Puguang 405079Guangrsquoan 135558Hecuan 118706Datianchi 106755Xinchang 84302Luojiazhai 79736Moxi 70231Wolonghe 40886Weiyuan 40861Tieshanpo 37397Dukouhe 359Bajiaochang 35107Luodai 32383Qiongxi 32325Qilibei 28221Baimamiao 26872Dachigan 25871Gaofengchang 22726Qilixia 22548Hebaochang 22212Tieshan 18782Zhongba 1863Majing 17558Xindu 17532Chongxi 13635Fuchengzhai 1033Jiannan 10025

Sichuan fold belt Central Sichuan low uplift and NorthwestSichuan depression

312 Stratigraphy The Sichuan Basin sedimentary strata arecomplete with a total thickness of 6000ndash12000m Only thePermian and the younger strata are considered in this paperas follows from old to new

Geofluids 7

III1

III1

III2

Southeast Sichuan fold belt

Central Sichuan low uplift

Northwest Sichuan depression

Longmen Mountai

n fault z

one

Long

quan

Mou

ntain

faul

t zon

e

Huayin Mountain

fault z

one

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Tectonic units

First-order tectonic units

Second-order tectonic units

0 50 100 (km)

Gas fields

Oil fields

Faults

II1

II2

I2

I1

AZhongbaGas Field

Huaying MountainZhangjiachang

Gas FieldDachiganjing

Gas Field

FangdoushanMountain

B

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

WolongheGas Field

300∘ang

Figure 2 Sichuan Basin geological structure unit zoning map There are three first-order tectonic units in the Sichuan Basin that is theSoutheast Sichuan fold belt the Central Sichuan low uplift and the Northwest Sichuan depression The Southeast Sichuan fold belt consistsof the high steep fold belt in Eastern Sichuan (I1) and the low steep bottom fold belt in Southern Sichuan (I2) the Central Sichuan low upliftis composed of the flat fold belt in Central Sichuan (II1) and the low steep fold belt in Southwestern Sichuan (II2) the Northwest Sichuandepression consists of the low-lying fold belt in Northern Sichuan (III1) and the low steep fold belt in Western Sichuan (III2)

(1) The Permian Liangshan group (P1l) Qixia group(P2q) Maokou group (P2m) Longtan group (P3l)and Changxing group (P3c)

(2) The Triassic Feixianguan group (T1f ) Jialing Group(T1j) Leikoupo group (T2l) Tianjingshan group(T2t) Marsquoantang group (T3m) Xiaotangzi group(T3t) and Xujiahe group

(3) The Jurassic Ziliujing group (J1z) Qianfoya group(J2q) Shaximiao group (J2s) Suining group (J3s) andPenglaizhen group (J3p)

(4) The Cretaceous (K) and the Quaternary (Q)

313 Hydrodynamic Condition The Sichuan Basin is essen-tially an artesian basin dominated by Permian and Triassic

8 Geofluids

Chengdu

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Highly confined aquifers

Confined aquifers

Semiconfined aquifers

Open aquifers

Groundwater flow direction

First-order tectonic units

Second-order tectonic units

0 50 100(km)

I

I

II

II

II

II

II

II

III

III

III

IIIIII

III

IV

IV

IV

Leshan

Figure 3 Hydrodynamic conditions in the Sichuan Basin The groundwater activities are very strong in the peripheral target exposure areaIn contrast the groundwater activities inside the basin are relatively weak with better hydrogeological confinement On the edge of themountain around the Sichuan Basin and the eastern fold belt experiencing infiltration of fresh water due to the complex structure and strongwater alternating

strata The upper Jurassic and Cretaceous formations aremostly a large set of terrestrial clastic sedimentary rocks withred sandstones and mudstones throughout the basin Theyare extremely thick with poor permeability generally lowin moisture but exceedingly uneven which could be goodcaprocks for the reservoirs below them The lower upperTriassic Xujiahe consists of sandstones and shale and thesandstone may be good aquifers for CO2 geological storagedue to its huge thickness The lower and middle Triassicand Permian carbonate rocks are the main saline aquifersin which Triassic carbonate rocks often form alternate layerswith evaporites Therefore an aqueous rock series based onmany stacked white aquifers is formed in the Sichuan Basin(Figure 3)

314 Geological Safety There are many late Quaternaryactive faults on the boundary of the Sichuan Basin forexample the Longmenshan fault zone in NorthwesternSichuan has experienced more intense activity in recentyears It is the induced fracture of the ldquo512rdquo Wenchuan 80earthquake The Lushan 70 earthquake on April 20 2013 is

another devastating earthquake that followed the Wenchuan80 earthquake nearly five years later It is also closely linkedwith the Longmenshan fault belt

However the crust in the Central and Eastern SichuanBasin is more stable Historical earthquakes with magnitudeabove 6 mainly took place in Western Sichuan and South-western Sichuan Basin And the peak ground accelerationzoning according to the GB 18306-2001 ldquoThe Peak GroundAcceleration Zoning in Chinardquo is shown in Figure 4

32 Oil and Gas Fields The Sichuan Basin has abundantnatural gas resources mainly in Eastern Sichuan but arelatively small amount of oil resources The petroleumgeological reserves in the Sichuan Basin amount to 438 times108 t and only 075 times 108 t of proven OOIP in Central andNorthern Sichuan flat structure area [38]

By the end of 2008 theMinistry of Land and Resources ofChina (MLR) announced 125 gas fields in the Sichuan Basin(Figure 1) and the total amount of proven OGIP is 1722502times 108m3 Among them there are 27 medium to large-sizedconfirmed gas fields with OGIP exceeding 100 times 108m3 of

Geofluids 9

gt015 g

gt015

g

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Seismic peak ground acceleration First-order tectonic units

Second-order tectonic unitsHistorical earthquakes (M 6ndash69)

010 gndash015g

lt005 g

lt005 g

lt005 g

lt005 g

gndash010g005

0 50 100(km)

Figure 4 Seismic peak ground acceleration and large historical earthquakes in the Sichuan Basin The peak ground acceleration is less than010 g in most parts of the Sichuan Basin Only in the western margin of the Sichuan Basin the peak ground acceleration is larger than 015 g

which the total natural gas reserves are 1509268 times 108m3accounting for 876 of the total proven OGIP in the basin(Table 7)

33 Unmineable Coal Seams The CBM geological reservesin the Sichuan Basin amount to 347140 times 108m3 in Sichuanprovince and Chongqing city 508457 times 108m3 in SouthernSichuan province and Northern Guizhou province respec-tively from 1000 to 2000meters depth [39] Among these thecoalfields in Southern Sichuan province are the most abun-dant accounting for 82 of the provincersquos total resources

34 Deep Saline Aquifers Comparedwith oil fields gas fieldsand unmineable coal seams the analysis of geological condi-tions for saline aquifers CO2 geological storage is muchmorecomplex The CO2 geological storage candidate prospectivearea for deep saline aquifers CO2 storage was selected fromthe map projection on the ground of all potential under-ground CO2 reservoirs In addition the hydrodynamic andgeological safety conditions must be studied to delineate thecandidate prospective areas

341 Candidate Prospective Area Delineation Standards Asmentioned above this report presents the delineation stan-dards of the CO2 geological storage candidate prospective

Table 8 Veto over key factors of CO2 geological storage candidateprospective areas delineation

Key factors VetoReservoir conditions

Layer thickness lt10mPorosity lt5Permeability lt1mD

Hydrogeological conditionsFormation water salinity lt3 gLGroundwater hydrodynamic condition Groundwater zone

Geological safety conditionsActive faults lt25 kmPeak ground acceleration ge040 g

areas shown in Table 8 Further potential and suitabilityassessments can be carried out for target area selection

342 Vertical Reservoir Cap Combination and CandidateProspective Areas Distribution The reservoirs for deep salineaquifer CO2 storage consist of the Permian the lower Triassiccarbonates and upper Triassic and Jurassic clastic reservoirs(Figure 5)The reservoir space includes carbonate karst poresand cracks and clastic pores and cracks Overall all reservoirs

10 Geofluids

Geochronology

Series Formation

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Penglaizhen

Suining

Shaximiao

Qianfoya

Ziliujing

Six

Xiaotangzi

Marsquoantang

Tianjingshan

Leikoupo

Changxing

Longtan

Maokou

Qixia

LiangshanCarbon-iferous

Permian

Upper

Stata

Middle

Lower

Upper

Upper

Middle

Middle

Lower

Lower

Five

Four

Three

Two

One

Four

Three

Two

One

Five

Four

Three

Two

One

Litho-histogram

D

depr

essio

nrift

Sandstone

Mudstone

Mud sandstone

Limestone

Dolomite

Reservoir

Caprock

Thick-ness(m)

Poro-sity()

Perme-ability(mD)

Coverage

Local

Regional

Regional

Regional

1244

5Local

Average

5Local

AverageLocal

10 5Local

10 5Local

Porefracture

Reservoirspace

fracture

Porefracture

Porefracture

Dissolved porefracture

Fracture-cave

Fracture-cave

Porefracture

525Average

605AverageLocal

Average

Dissolved pore

Dissolved pore

Rese

rvoi

r

Capr

ock

Tect

onic

mov

emen

tBa

sinev

olut

ion

Mid

dle Y

ansh

an

Fore

land

Late

Indo

sinia

n

Intr

acra

toni

c

ongw

u

Pore

001ndash10

gt1

gt200

gt1

gt1gt6

gt7

gt1

gt1

gt8gt10

gt1

gt1

gt1725

4ndash10

6ndash80

25ndash70

25ndash30

100ndash200

100ndash200

0ndash300

Jialin

gjia

ngFe

ixia

ngua

nXu

jiahe

Figure 5 CO2 geological storage vertical reservoir cap combination in the Sichuan Basin There are nine sets of reservoirs in the SichuanBasin and the section four of Xujiahe group is the primary reservoir with large thickness and area which almost cover the whole basin

Geofluids 11

Table 9 Storage potential of CO2 geological storage in depleted oil fields

Tectonic unit OOIP108 t Oil density(kgm3) 119861 (mdash) Reservoir

pressureMpaOil

temperature∘C120588CO2

(kgm3)119864oil 119866CO2

108 t

Central Sichuan flatstructure area 058 850 118 2126 6442 71263 075 057

Northern Sichuan flatstructure area 017 850 118 2126 6442 71263 075 017

Table 10 CO2-EOR geological storage potential in the Sichuan Basin

Tectonic unit API EXTRA () 119875LCO2() 119875HCO2

() 119864oil 119866CO2-EOR108 t

Central Sichuan flatstructure area 3497 1046 33 66 075 016

Northern Sichuan flatstructure area 3497 1046 33 66 075 005

in the Sichuan Basin have poor physical properties withultra-low porosity and low permeability Comparing withthe natural gas fields in the Sichuan Basin these reservoirsfor CO2 storage have better caprock conditions too Forexample the extensive deposits of gypsum rocks in theLeikoupo phase and the widely developed dark mudstone inthe Lower Jurassic can provide good sealing conditions forthe underlying reservoirs

(1) The Permian The reef flat facies on the top of Qixiagroup form a good reservoir through dolomitization withfavorable reservoir conditions (P2q) [40] Part of them formthe natural gas reservoirs with a thickness of approximately10m Similar to the Qixia group the Maokou group (P2m)is a fracture-cave type of reservoir Changxing group (P3c)reservoirs are pore type and fracture-pore type The porosityis generally 203ndash1585 with an average value of 525 thepermeability is less than 1000mD with an average value of605mD The reservoir thickness is large with a monolayerthickness of 05ndash5m and a single well cumulative thicknessof 25ndash70m [41]

(2) The Triassic The Feixianguan group (T1f ) is similar tothe Changxing groupThe quality and distribution of the reefbeach reservoir are mainly controlled by sedimentary faciesand diagenesis The evaporative platform oolitic dolomitereservoir is mainly distributed in Northeast Sichuan witha monolayer thickness of 15ndash15m and total thickness of20ndash50m The porosity ranges from 2 to 268 on theaverage of 829 and the permeability is less than 1160mDwith an average value of 5973mD The porosity of the openplatform edge oolitic dolomite reservoir is 205ndash2262 onthe average of 842 and the permeability is less than 410mDwith an average value of 1725mD The reservoir monolayerthickness is generally 05ndash6m and the total thickness is10ndash45m typically

The favorable Jialingjiang reservoir facies are the platforminterior shoal and the platform margin shoal facies Forexample section five of Jialingjiang reservoirs consists oflimestone and dolomite with a thickness of 25ndash30m ofwhich approximately 60 is the porosity layer and the

average of the porosity is 5 with the highest value reaching18

The sandstone aquifers in section two section four andsection six of Xujiahe formation could be reservoirs for CO2geological storage composed of residual intergranular poreintergranular dissolved pore and fracture The sand ratioof the sandstones is greater than 70 in 80 generally Inaddition the porosity of section four is higher than sectiontwo and section six usually between 5ndash10 while theporosity of sandstones in section two and section is less than7 generally

Figure 6 shows the candidate prospective areas in theSichuan Basin in the Sichuan Basin for deep saline aquiferCO2 storage based on geology study

4 Results

41 Potential

411 Depleted Oil Fields CO2 Storage and CO2-EOR Theprimary CO2-EOR prospective areas in the Sichuan Basinare located in the flat tectonic area in Central and NorthernSichuan Basin As shown in Tables 9 and 10 the CO2geological storage potential of storage in depleted oil fieldsis only 074 times 108 t while the storage potential is about 021 times108 t by using CO2-EOR technology

412 Depleted Gas Fields CO2 Storage and CO2-EGR TheCO2 geological storage potential of depleted gas fields is 5373times 108 t By using CO2-EGR technology the Sichuan Basin gasfields could achieve CO2 geological storage of 3385 times 108 tAmong that 27 large and medium gas fields have the greatestpotential with the possibility of achieving a CO2 geologicalstorage capacity of 4239 times 108 t in depleted gas fields whilethe storage potential is about 2670 times 108 t by using CO2-EGRtechnology

413 Unmineable Coal Seams CO2 Storage and CO2-ECBMThe Sichuan Basin has abundant coal bedmethane resourcesAs shown in Table 11 the total CO2 geological storage

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

6 Geofluids

01 50 100 150 200 250 300 350

100

200

300

400

500

Number of basins

Stor

age p

oten

tial (

km2)

Figure 1 The statistical profile of CO2 geological storage potential per square kilometer of 390 onshore basins in China

leakage through the caprock According to the GB 17741-2005ldquoProject site seismic safety evaluationrdquo [33] the identificationof the capable fault has to be made within a 5 km range of thefirst class venues and epitaxy For seismic safety evaluationthe near-field region should be extended to a radius of 25 kmrange Therefore areas within 25 km of the active faults areinappropriate as the candidate prospective areas

Development Degree of Fractures CO2 could leak by tectonicpathways including faults fractures and ground fissures (eg[28 34ndash36]) Due to the complexity of geological structureand faults development in the Sichuan Basin the qualitativeassessment is based on the faults development and theexisting seismic data The more complex the fault systemis the more unfavorable it is for CO2 geological storage Inaddition there have been more frequent seismic activities inthe Sichuan Basin in recent years

(4) Storage Potential per Unit Area Guo (2014) evaluated thenational scale potential of CO2 geological storage in deepsaline aquifers of 390 onshore basins in China supported byChina Geological Survey As shown in Figure 1 the potentialof CO2 geological storage in deep saline aquifers in most ofthe sedimentary basins is 50 times 104ndash100 times 104 t generally anda small part of the basins are less than 10 times 104 t or more than100 times 104 t3 Candidate Prospective Areas for CO2Geological Utilization and Storage

The fine forming conditions of the reservoir mediums foroil gas and CBM make them possible that the existing oiland gas fields under production are the mesoscale candidateprospective areas or target areas in the short future Becauseof no official basin-scale data available the CO2 storagepotential of other CO2 geological utilization technologies isnot discussed further in this paper

31 Geology

311 Geostructure As shown in Figure 2 [37] the currentgeostructure of the Sichuan Basin consists of the Southeast

Table 7 Proven OGIP of 27 natural gas fields in the Sichuan Basin

Gas fields OGIP108m3

Puguang 405079Guangrsquoan 135558Hecuan 118706Datianchi 106755Xinchang 84302Luojiazhai 79736Moxi 70231Wolonghe 40886Weiyuan 40861Tieshanpo 37397Dukouhe 359Bajiaochang 35107Luodai 32383Qiongxi 32325Qilibei 28221Baimamiao 26872Dachigan 25871Gaofengchang 22726Qilixia 22548Hebaochang 22212Tieshan 18782Zhongba 1863Majing 17558Xindu 17532Chongxi 13635Fuchengzhai 1033Jiannan 10025

Sichuan fold belt Central Sichuan low uplift and NorthwestSichuan depression

312 Stratigraphy The Sichuan Basin sedimentary strata arecomplete with a total thickness of 6000ndash12000m Only thePermian and the younger strata are considered in this paperas follows from old to new

Geofluids 7

III1

III1

III2

Southeast Sichuan fold belt

Central Sichuan low uplift

Northwest Sichuan depression

Longmen Mountai

n fault z

one

Long

quan

Mou

ntain

faul

t zon

e

Huayin Mountain

fault z

one

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Tectonic units

First-order tectonic units

Second-order tectonic units

0 50 100 (km)

Gas fields

Oil fields

Faults

II1

II2

I2

I1

AZhongbaGas Field

Huaying MountainZhangjiachang

Gas FieldDachiganjing

Gas Field

FangdoushanMountain

B

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

WolongheGas Field

300∘ang

Figure 2 Sichuan Basin geological structure unit zoning map There are three first-order tectonic units in the Sichuan Basin that is theSoutheast Sichuan fold belt the Central Sichuan low uplift and the Northwest Sichuan depression The Southeast Sichuan fold belt consistsof the high steep fold belt in Eastern Sichuan (I1) and the low steep bottom fold belt in Southern Sichuan (I2) the Central Sichuan low upliftis composed of the flat fold belt in Central Sichuan (II1) and the low steep fold belt in Southwestern Sichuan (II2) the Northwest Sichuandepression consists of the low-lying fold belt in Northern Sichuan (III1) and the low steep fold belt in Western Sichuan (III2)

(1) The Permian Liangshan group (P1l) Qixia group(P2q) Maokou group (P2m) Longtan group (P3l)and Changxing group (P3c)

(2) The Triassic Feixianguan group (T1f ) Jialing Group(T1j) Leikoupo group (T2l) Tianjingshan group(T2t) Marsquoantang group (T3m) Xiaotangzi group(T3t) and Xujiahe group

(3) The Jurassic Ziliujing group (J1z) Qianfoya group(J2q) Shaximiao group (J2s) Suining group (J3s) andPenglaizhen group (J3p)

(4) The Cretaceous (K) and the Quaternary (Q)

313 Hydrodynamic Condition The Sichuan Basin is essen-tially an artesian basin dominated by Permian and Triassic

8 Geofluids

Chengdu

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Highly confined aquifers

Confined aquifers

Semiconfined aquifers

Open aquifers

Groundwater flow direction

First-order tectonic units

Second-order tectonic units

0 50 100(km)

I

I

II

II

II

II

II

II

III

III

III

IIIIII

III

IV

IV

IV

Leshan

Figure 3 Hydrodynamic conditions in the Sichuan Basin The groundwater activities are very strong in the peripheral target exposure areaIn contrast the groundwater activities inside the basin are relatively weak with better hydrogeological confinement On the edge of themountain around the Sichuan Basin and the eastern fold belt experiencing infiltration of fresh water due to the complex structure and strongwater alternating

strata The upper Jurassic and Cretaceous formations aremostly a large set of terrestrial clastic sedimentary rocks withred sandstones and mudstones throughout the basin Theyare extremely thick with poor permeability generally lowin moisture but exceedingly uneven which could be goodcaprocks for the reservoirs below them The lower upperTriassic Xujiahe consists of sandstones and shale and thesandstone may be good aquifers for CO2 geological storagedue to its huge thickness The lower and middle Triassicand Permian carbonate rocks are the main saline aquifersin which Triassic carbonate rocks often form alternate layerswith evaporites Therefore an aqueous rock series based onmany stacked white aquifers is formed in the Sichuan Basin(Figure 3)

314 Geological Safety There are many late Quaternaryactive faults on the boundary of the Sichuan Basin forexample the Longmenshan fault zone in NorthwesternSichuan has experienced more intense activity in recentyears It is the induced fracture of the ldquo512rdquo Wenchuan 80earthquake The Lushan 70 earthquake on April 20 2013 is

another devastating earthquake that followed the Wenchuan80 earthquake nearly five years later It is also closely linkedwith the Longmenshan fault belt

However the crust in the Central and Eastern SichuanBasin is more stable Historical earthquakes with magnitudeabove 6 mainly took place in Western Sichuan and South-western Sichuan Basin And the peak ground accelerationzoning according to the GB 18306-2001 ldquoThe Peak GroundAcceleration Zoning in Chinardquo is shown in Figure 4

32 Oil and Gas Fields The Sichuan Basin has abundantnatural gas resources mainly in Eastern Sichuan but arelatively small amount of oil resources The petroleumgeological reserves in the Sichuan Basin amount to 438 times108 t and only 075 times 108 t of proven OOIP in Central andNorthern Sichuan flat structure area [38]

By the end of 2008 theMinistry of Land and Resources ofChina (MLR) announced 125 gas fields in the Sichuan Basin(Figure 1) and the total amount of proven OGIP is 1722502times 108m3 Among them there are 27 medium to large-sizedconfirmed gas fields with OGIP exceeding 100 times 108m3 of

Geofluids 9

gt015 g

gt015

g

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Seismic peak ground acceleration First-order tectonic units

Second-order tectonic unitsHistorical earthquakes (M 6ndash69)

010 gndash015g

lt005 g

lt005 g

lt005 g

lt005 g

gndash010g005

0 50 100(km)

Figure 4 Seismic peak ground acceleration and large historical earthquakes in the Sichuan Basin The peak ground acceleration is less than010 g in most parts of the Sichuan Basin Only in the western margin of the Sichuan Basin the peak ground acceleration is larger than 015 g

which the total natural gas reserves are 1509268 times 108m3accounting for 876 of the total proven OGIP in the basin(Table 7)

33 Unmineable Coal Seams The CBM geological reservesin the Sichuan Basin amount to 347140 times 108m3 in Sichuanprovince and Chongqing city 508457 times 108m3 in SouthernSichuan province and Northern Guizhou province respec-tively from 1000 to 2000meters depth [39] Among these thecoalfields in Southern Sichuan province are the most abun-dant accounting for 82 of the provincersquos total resources

34 Deep Saline Aquifers Comparedwith oil fields gas fieldsand unmineable coal seams the analysis of geological condi-tions for saline aquifers CO2 geological storage is muchmorecomplex The CO2 geological storage candidate prospectivearea for deep saline aquifers CO2 storage was selected fromthe map projection on the ground of all potential under-ground CO2 reservoirs In addition the hydrodynamic andgeological safety conditions must be studied to delineate thecandidate prospective areas

341 Candidate Prospective Area Delineation Standards Asmentioned above this report presents the delineation stan-dards of the CO2 geological storage candidate prospective

Table 8 Veto over key factors of CO2 geological storage candidateprospective areas delineation

Key factors VetoReservoir conditions

Layer thickness lt10mPorosity lt5Permeability lt1mD

Hydrogeological conditionsFormation water salinity lt3 gLGroundwater hydrodynamic condition Groundwater zone

Geological safety conditionsActive faults lt25 kmPeak ground acceleration ge040 g

areas shown in Table 8 Further potential and suitabilityassessments can be carried out for target area selection

342 Vertical Reservoir Cap Combination and CandidateProspective Areas Distribution The reservoirs for deep salineaquifer CO2 storage consist of the Permian the lower Triassiccarbonates and upper Triassic and Jurassic clastic reservoirs(Figure 5)The reservoir space includes carbonate karst poresand cracks and clastic pores and cracks Overall all reservoirs

10 Geofluids

Geochronology

Series Formation

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Penglaizhen

Suining

Shaximiao

Qianfoya

Ziliujing

Six

Xiaotangzi

Marsquoantang

Tianjingshan

Leikoupo

Changxing

Longtan

Maokou

Qixia

LiangshanCarbon-iferous

Permian

Upper

Stata

Middle

Lower

Upper

Upper

Middle

Middle

Lower

Lower

Five

Four

Three

Two

One

Four

Three

Two

One

Five

Four

Three

Two

One

Litho-histogram

D

depr

essio

nrift

Sandstone

Mudstone

Mud sandstone

Limestone

Dolomite

Reservoir

Caprock

Thick-ness(m)

Poro-sity()

Perme-ability(mD)

Coverage

Local

Regional

Regional

Regional

1244

5Local

Average

5Local

AverageLocal

10 5Local

10 5Local

Porefracture

Reservoirspace

fracture

Porefracture

Porefracture

Dissolved porefracture

Fracture-cave

Fracture-cave

Porefracture

525Average

605AverageLocal

Average

Dissolved pore

Dissolved pore

Rese

rvoi

r

Capr

ock

Tect

onic

mov

emen

tBa

sinev

olut

ion

Mid

dle Y

ansh

an

Fore

land

Late

Indo

sinia

n

Intr

acra

toni

c

ongw

u

Pore

001ndash10

gt1

gt200

gt1

gt1gt6

gt7

gt1

gt1

gt8gt10

gt1

gt1

gt1725

4ndash10

6ndash80

25ndash70

25ndash30

100ndash200

100ndash200

0ndash300

Jialin

gjia

ngFe

ixia

ngua

nXu

jiahe

Figure 5 CO2 geological storage vertical reservoir cap combination in the Sichuan Basin There are nine sets of reservoirs in the SichuanBasin and the section four of Xujiahe group is the primary reservoir with large thickness and area which almost cover the whole basin

Geofluids 11

Table 9 Storage potential of CO2 geological storage in depleted oil fields

Tectonic unit OOIP108 t Oil density(kgm3) 119861 (mdash) Reservoir

pressureMpaOil

temperature∘C120588CO2

(kgm3)119864oil 119866CO2

108 t

Central Sichuan flatstructure area 058 850 118 2126 6442 71263 075 057

Northern Sichuan flatstructure area 017 850 118 2126 6442 71263 075 017

Table 10 CO2-EOR geological storage potential in the Sichuan Basin

Tectonic unit API EXTRA () 119875LCO2() 119875HCO2

() 119864oil 119866CO2-EOR108 t

Central Sichuan flatstructure area 3497 1046 33 66 075 016

Northern Sichuan flatstructure area 3497 1046 33 66 075 005

in the Sichuan Basin have poor physical properties withultra-low porosity and low permeability Comparing withthe natural gas fields in the Sichuan Basin these reservoirsfor CO2 storage have better caprock conditions too Forexample the extensive deposits of gypsum rocks in theLeikoupo phase and the widely developed dark mudstone inthe Lower Jurassic can provide good sealing conditions forthe underlying reservoirs

(1) The Permian The reef flat facies on the top of Qixiagroup form a good reservoir through dolomitization withfavorable reservoir conditions (P2q) [40] Part of them formthe natural gas reservoirs with a thickness of approximately10m Similar to the Qixia group the Maokou group (P2m)is a fracture-cave type of reservoir Changxing group (P3c)reservoirs are pore type and fracture-pore type The porosityis generally 203ndash1585 with an average value of 525 thepermeability is less than 1000mD with an average value of605mD The reservoir thickness is large with a monolayerthickness of 05ndash5m and a single well cumulative thicknessof 25ndash70m [41]

(2) The Triassic The Feixianguan group (T1f ) is similar tothe Changxing groupThe quality and distribution of the reefbeach reservoir are mainly controlled by sedimentary faciesand diagenesis The evaporative platform oolitic dolomitereservoir is mainly distributed in Northeast Sichuan witha monolayer thickness of 15ndash15m and total thickness of20ndash50m The porosity ranges from 2 to 268 on theaverage of 829 and the permeability is less than 1160mDwith an average value of 5973mD The porosity of the openplatform edge oolitic dolomite reservoir is 205ndash2262 onthe average of 842 and the permeability is less than 410mDwith an average value of 1725mD The reservoir monolayerthickness is generally 05ndash6m and the total thickness is10ndash45m typically

The favorable Jialingjiang reservoir facies are the platforminterior shoal and the platform margin shoal facies Forexample section five of Jialingjiang reservoirs consists oflimestone and dolomite with a thickness of 25ndash30m ofwhich approximately 60 is the porosity layer and the

average of the porosity is 5 with the highest value reaching18

The sandstone aquifers in section two section four andsection six of Xujiahe formation could be reservoirs for CO2geological storage composed of residual intergranular poreintergranular dissolved pore and fracture The sand ratioof the sandstones is greater than 70 in 80 generally Inaddition the porosity of section four is higher than sectiontwo and section six usually between 5ndash10 while theporosity of sandstones in section two and section is less than7 generally

Figure 6 shows the candidate prospective areas in theSichuan Basin in the Sichuan Basin for deep saline aquiferCO2 storage based on geology study

4 Results

41 Potential

411 Depleted Oil Fields CO2 Storage and CO2-EOR Theprimary CO2-EOR prospective areas in the Sichuan Basinare located in the flat tectonic area in Central and NorthernSichuan Basin As shown in Tables 9 and 10 the CO2geological storage potential of storage in depleted oil fieldsis only 074 times 108 t while the storage potential is about 021 times108 t by using CO2-EOR technology

412 Depleted Gas Fields CO2 Storage and CO2-EGR TheCO2 geological storage potential of depleted gas fields is 5373times 108 t By using CO2-EGR technology the Sichuan Basin gasfields could achieve CO2 geological storage of 3385 times 108 tAmong that 27 large and medium gas fields have the greatestpotential with the possibility of achieving a CO2 geologicalstorage capacity of 4239 times 108 t in depleted gas fields whilethe storage potential is about 2670 times 108 t by using CO2-EGRtechnology

413 Unmineable Coal Seams CO2 Storage and CO2-ECBMThe Sichuan Basin has abundant coal bedmethane resourcesAs shown in Table 11 the total CO2 geological storage

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

Geofluids 7

III1

III1

III2

Southeast Sichuan fold belt

Central Sichuan low uplift

Northwest Sichuan depression

Longmen Mountai

n fault z

one

Long

quan

Mou

ntain

faul

t zon

e

Huayin Mountain

fault z

one

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Tectonic units

First-order tectonic units

Second-order tectonic units

0 50 100 (km)

Gas fields

Oil fields

Faults

II1

II2

I2

I1

AZhongbaGas Field

Huaying MountainZhangjiachang

Gas FieldDachiganjing

Gas Field

FangdoushanMountain

B

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

0(km)

Altitude

minus2

minus4

minus6

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

WolongheGas Field

300∘ang

Figure 2 Sichuan Basin geological structure unit zoning map There are three first-order tectonic units in the Sichuan Basin that is theSoutheast Sichuan fold belt the Central Sichuan low uplift and the Northwest Sichuan depression The Southeast Sichuan fold belt consistsof the high steep fold belt in Eastern Sichuan (I1) and the low steep bottom fold belt in Southern Sichuan (I2) the Central Sichuan low upliftis composed of the flat fold belt in Central Sichuan (II1) and the low steep fold belt in Southwestern Sichuan (II2) the Northwest Sichuandepression consists of the low-lying fold belt in Northern Sichuan (III1) and the low steep fold belt in Western Sichuan (III2)

(1) The Permian Liangshan group (P1l) Qixia group(P2q) Maokou group (P2m) Longtan group (P3l)and Changxing group (P3c)

(2) The Triassic Feixianguan group (T1f ) Jialing Group(T1j) Leikoupo group (T2l) Tianjingshan group(T2t) Marsquoantang group (T3m) Xiaotangzi group(T3t) and Xujiahe group

(3) The Jurassic Ziliujing group (J1z) Qianfoya group(J2q) Shaximiao group (J2s) Suining group (J3s) andPenglaizhen group (J3p)

(4) The Cretaceous (K) and the Quaternary (Q)

313 Hydrodynamic Condition The Sichuan Basin is essen-tially an artesian basin dominated by Permian and Triassic

8 Geofluids

Chengdu

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Highly confined aquifers

Confined aquifers

Semiconfined aquifers

Open aquifers

Groundwater flow direction

First-order tectonic units

Second-order tectonic units

0 50 100(km)

I

I

II

II

II

II

II

II

III

III

III

IIIIII

III

IV

IV

IV

Leshan

Figure 3 Hydrodynamic conditions in the Sichuan Basin The groundwater activities are very strong in the peripheral target exposure areaIn contrast the groundwater activities inside the basin are relatively weak with better hydrogeological confinement On the edge of themountain around the Sichuan Basin and the eastern fold belt experiencing infiltration of fresh water due to the complex structure and strongwater alternating

strata The upper Jurassic and Cretaceous formations aremostly a large set of terrestrial clastic sedimentary rocks withred sandstones and mudstones throughout the basin Theyare extremely thick with poor permeability generally lowin moisture but exceedingly uneven which could be goodcaprocks for the reservoirs below them The lower upperTriassic Xujiahe consists of sandstones and shale and thesandstone may be good aquifers for CO2 geological storagedue to its huge thickness The lower and middle Triassicand Permian carbonate rocks are the main saline aquifersin which Triassic carbonate rocks often form alternate layerswith evaporites Therefore an aqueous rock series based onmany stacked white aquifers is formed in the Sichuan Basin(Figure 3)

314 Geological Safety There are many late Quaternaryactive faults on the boundary of the Sichuan Basin forexample the Longmenshan fault zone in NorthwesternSichuan has experienced more intense activity in recentyears It is the induced fracture of the ldquo512rdquo Wenchuan 80earthquake The Lushan 70 earthquake on April 20 2013 is

another devastating earthquake that followed the Wenchuan80 earthquake nearly five years later It is also closely linkedwith the Longmenshan fault belt

However the crust in the Central and Eastern SichuanBasin is more stable Historical earthquakes with magnitudeabove 6 mainly took place in Western Sichuan and South-western Sichuan Basin And the peak ground accelerationzoning according to the GB 18306-2001 ldquoThe Peak GroundAcceleration Zoning in Chinardquo is shown in Figure 4

32 Oil and Gas Fields The Sichuan Basin has abundantnatural gas resources mainly in Eastern Sichuan but arelatively small amount of oil resources The petroleumgeological reserves in the Sichuan Basin amount to 438 times108 t and only 075 times 108 t of proven OOIP in Central andNorthern Sichuan flat structure area [38]

By the end of 2008 theMinistry of Land and Resources ofChina (MLR) announced 125 gas fields in the Sichuan Basin(Figure 1) and the total amount of proven OGIP is 1722502times 108m3 Among them there are 27 medium to large-sizedconfirmed gas fields with OGIP exceeding 100 times 108m3 of

Geofluids 9

gt015 g

gt015

g

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Seismic peak ground acceleration First-order tectonic units

Second-order tectonic unitsHistorical earthquakes (M 6ndash69)

010 gndash015g

lt005 g

lt005 g

lt005 g

lt005 g

gndash010g005

0 50 100(km)

Figure 4 Seismic peak ground acceleration and large historical earthquakes in the Sichuan Basin The peak ground acceleration is less than010 g in most parts of the Sichuan Basin Only in the western margin of the Sichuan Basin the peak ground acceleration is larger than 015 g

which the total natural gas reserves are 1509268 times 108m3accounting for 876 of the total proven OGIP in the basin(Table 7)

33 Unmineable Coal Seams The CBM geological reservesin the Sichuan Basin amount to 347140 times 108m3 in Sichuanprovince and Chongqing city 508457 times 108m3 in SouthernSichuan province and Northern Guizhou province respec-tively from 1000 to 2000meters depth [39] Among these thecoalfields in Southern Sichuan province are the most abun-dant accounting for 82 of the provincersquos total resources

34 Deep Saline Aquifers Comparedwith oil fields gas fieldsand unmineable coal seams the analysis of geological condi-tions for saline aquifers CO2 geological storage is muchmorecomplex The CO2 geological storage candidate prospectivearea for deep saline aquifers CO2 storage was selected fromthe map projection on the ground of all potential under-ground CO2 reservoirs In addition the hydrodynamic andgeological safety conditions must be studied to delineate thecandidate prospective areas

341 Candidate Prospective Area Delineation Standards Asmentioned above this report presents the delineation stan-dards of the CO2 geological storage candidate prospective

Table 8 Veto over key factors of CO2 geological storage candidateprospective areas delineation

Key factors VetoReservoir conditions

Layer thickness lt10mPorosity lt5Permeability lt1mD

Hydrogeological conditionsFormation water salinity lt3 gLGroundwater hydrodynamic condition Groundwater zone

Geological safety conditionsActive faults lt25 kmPeak ground acceleration ge040 g

areas shown in Table 8 Further potential and suitabilityassessments can be carried out for target area selection

342 Vertical Reservoir Cap Combination and CandidateProspective Areas Distribution The reservoirs for deep salineaquifer CO2 storage consist of the Permian the lower Triassiccarbonates and upper Triassic and Jurassic clastic reservoirs(Figure 5)The reservoir space includes carbonate karst poresand cracks and clastic pores and cracks Overall all reservoirs

10 Geofluids

Geochronology

Series Formation

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Penglaizhen

Suining

Shaximiao

Qianfoya

Ziliujing

Six

Xiaotangzi

Marsquoantang

Tianjingshan

Leikoupo

Changxing

Longtan

Maokou

Qixia

LiangshanCarbon-iferous

Permian

Upper

Stata

Middle

Lower

Upper

Upper

Middle

Middle

Lower

Lower

Five

Four

Three

Two

One

Four

Three

Two

One

Five

Four

Three

Two

One

Litho-histogram

D

depr

essio

nrift

Sandstone

Mudstone

Mud sandstone

Limestone

Dolomite

Reservoir

Caprock

Thick-ness(m)

Poro-sity()

Perme-ability(mD)

Coverage

Local

Regional

Regional

Regional

1244

5Local

Average

5Local

AverageLocal

10 5Local

10 5Local

Porefracture

Reservoirspace

fracture

Porefracture

Porefracture

Dissolved porefracture

Fracture-cave

Fracture-cave

Porefracture

525Average

605AverageLocal

Average

Dissolved pore

Dissolved pore

Rese

rvoi

r

Capr

ock

Tect

onic

mov

emen

tBa

sinev

olut

ion

Mid

dle Y

ansh

an

Fore

land

Late

Indo

sinia

n

Intr

acra

toni

c

ongw

u

Pore

001ndash10

gt1

gt200

gt1

gt1gt6

gt7

gt1

gt1

gt8gt10

gt1

gt1

gt1725

4ndash10

6ndash80

25ndash70

25ndash30

100ndash200

100ndash200

0ndash300

Jialin

gjia

ngFe

ixia

ngua

nXu

jiahe

Figure 5 CO2 geological storage vertical reservoir cap combination in the Sichuan Basin There are nine sets of reservoirs in the SichuanBasin and the section four of Xujiahe group is the primary reservoir with large thickness and area which almost cover the whole basin

Geofluids 11

Table 9 Storage potential of CO2 geological storage in depleted oil fields

Tectonic unit OOIP108 t Oil density(kgm3) 119861 (mdash) Reservoir

pressureMpaOil

temperature∘C120588CO2

(kgm3)119864oil 119866CO2

108 t

Central Sichuan flatstructure area 058 850 118 2126 6442 71263 075 057

Northern Sichuan flatstructure area 017 850 118 2126 6442 71263 075 017

Table 10 CO2-EOR geological storage potential in the Sichuan Basin

Tectonic unit API EXTRA () 119875LCO2() 119875HCO2

() 119864oil 119866CO2-EOR108 t

Central Sichuan flatstructure area 3497 1046 33 66 075 016

Northern Sichuan flatstructure area 3497 1046 33 66 075 005

in the Sichuan Basin have poor physical properties withultra-low porosity and low permeability Comparing withthe natural gas fields in the Sichuan Basin these reservoirsfor CO2 storage have better caprock conditions too Forexample the extensive deposits of gypsum rocks in theLeikoupo phase and the widely developed dark mudstone inthe Lower Jurassic can provide good sealing conditions forthe underlying reservoirs

(1) The Permian The reef flat facies on the top of Qixiagroup form a good reservoir through dolomitization withfavorable reservoir conditions (P2q) [40] Part of them formthe natural gas reservoirs with a thickness of approximately10m Similar to the Qixia group the Maokou group (P2m)is a fracture-cave type of reservoir Changxing group (P3c)reservoirs are pore type and fracture-pore type The porosityis generally 203ndash1585 with an average value of 525 thepermeability is less than 1000mD with an average value of605mD The reservoir thickness is large with a monolayerthickness of 05ndash5m and a single well cumulative thicknessof 25ndash70m [41]

(2) The Triassic The Feixianguan group (T1f ) is similar tothe Changxing groupThe quality and distribution of the reefbeach reservoir are mainly controlled by sedimentary faciesand diagenesis The evaporative platform oolitic dolomitereservoir is mainly distributed in Northeast Sichuan witha monolayer thickness of 15ndash15m and total thickness of20ndash50m The porosity ranges from 2 to 268 on theaverage of 829 and the permeability is less than 1160mDwith an average value of 5973mD The porosity of the openplatform edge oolitic dolomite reservoir is 205ndash2262 onthe average of 842 and the permeability is less than 410mDwith an average value of 1725mD The reservoir monolayerthickness is generally 05ndash6m and the total thickness is10ndash45m typically

The favorable Jialingjiang reservoir facies are the platforminterior shoal and the platform margin shoal facies Forexample section five of Jialingjiang reservoirs consists oflimestone and dolomite with a thickness of 25ndash30m ofwhich approximately 60 is the porosity layer and the

average of the porosity is 5 with the highest value reaching18

The sandstone aquifers in section two section four andsection six of Xujiahe formation could be reservoirs for CO2geological storage composed of residual intergranular poreintergranular dissolved pore and fracture The sand ratioof the sandstones is greater than 70 in 80 generally Inaddition the porosity of section four is higher than sectiontwo and section six usually between 5ndash10 while theporosity of sandstones in section two and section is less than7 generally

Figure 6 shows the candidate prospective areas in theSichuan Basin in the Sichuan Basin for deep saline aquiferCO2 storage based on geology study

4 Results

41 Potential

411 Depleted Oil Fields CO2 Storage and CO2-EOR Theprimary CO2-EOR prospective areas in the Sichuan Basinare located in the flat tectonic area in Central and NorthernSichuan Basin As shown in Tables 9 and 10 the CO2geological storage potential of storage in depleted oil fieldsis only 074 times 108 t while the storage potential is about 021 times108 t by using CO2-EOR technology

412 Depleted Gas Fields CO2 Storage and CO2-EGR TheCO2 geological storage potential of depleted gas fields is 5373times 108 t By using CO2-EGR technology the Sichuan Basin gasfields could achieve CO2 geological storage of 3385 times 108 tAmong that 27 large and medium gas fields have the greatestpotential with the possibility of achieving a CO2 geologicalstorage capacity of 4239 times 108 t in depleted gas fields whilethe storage potential is about 2670 times 108 t by using CO2-EGRtechnology

413 Unmineable Coal Seams CO2 Storage and CO2-ECBMThe Sichuan Basin has abundant coal bedmethane resourcesAs shown in Table 11 the total CO2 geological storage

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

8 Geofluids

Chengdu

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Highly confined aquifers

Confined aquifers

Semiconfined aquifers

Open aquifers

Groundwater flow direction

First-order tectonic units

Second-order tectonic units

0 50 100(km)

I

I

II

II

II

II

II

II

III

III

III

IIIIII

III

IV

IV

IV

Leshan

Figure 3 Hydrodynamic conditions in the Sichuan Basin The groundwater activities are very strong in the peripheral target exposure areaIn contrast the groundwater activities inside the basin are relatively weak with better hydrogeological confinement On the edge of themountain around the Sichuan Basin and the eastern fold belt experiencing infiltration of fresh water due to the complex structure and strongwater alternating

strata The upper Jurassic and Cretaceous formations aremostly a large set of terrestrial clastic sedimentary rocks withred sandstones and mudstones throughout the basin Theyare extremely thick with poor permeability generally lowin moisture but exceedingly uneven which could be goodcaprocks for the reservoirs below them The lower upperTriassic Xujiahe consists of sandstones and shale and thesandstone may be good aquifers for CO2 geological storagedue to its huge thickness The lower and middle Triassicand Permian carbonate rocks are the main saline aquifersin which Triassic carbonate rocks often form alternate layerswith evaporites Therefore an aqueous rock series based onmany stacked white aquifers is formed in the Sichuan Basin(Figure 3)

314 Geological Safety There are many late Quaternaryactive faults on the boundary of the Sichuan Basin forexample the Longmenshan fault zone in NorthwesternSichuan has experienced more intense activity in recentyears It is the induced fracture of the ldquo512rdquo Wenchuan 80earthquake The Lushan 70 earthquake on April 20 2013 is

another devastating earthquake that followed the Wenchuan80 earthquake nearly five years later It is also closely linkedwith the Longmenshan fault belt

However the crust in the Central and Eastern SichuanBasin is more stable Historical earthquakes with magnitudeabove 6 mainly took place in Western Sichuan and South-western Sichuan Basin And the peak ground accelerationzoning according to the GB 18306-2001 ldquoThe Peak GroundAcceleration Zoning in Chinardquo is shown in Figure 4

32 Oil and Gas Fields The Sichuan Basin has abundantnatural gas resources mainly in Eastern Sichuan but arelatively small amount of oil resources The petroleumgeological reserves in the Sichuan Basin amount to 438 times108 t and only 075 times 108 t of proven OOIP in Central andNorthern Sichuan flat structure area [38]

By the end of 2008 theMinistry of Land and Resources ofChina (MLR) announced 125 gas fields in the Sichuan Basin(Figure 1) and the total amount of proven OGIP is 1722502times 108m3 Among them there are 27 medium to large-sizedconfirmed gas fields with OGIP exceeding 100 times 108m3 of

Geofluids 9

gt015 g

gt015

g

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Seismic peak ground acceleration First-order tectonic units

Second-order tectonic unitsHistorical earthquakes (M 6ndash69)

010 gndash015g

lt005 g

lt005 g

lt005 g

lt005 g

gndash010g005

0 50 100(km)

Figure 4 Seismic peak ground acceleration and large historical earthquakes in the Sichuan Basin The peak ground acceleration is less than010 g in most parts of the Sichuan Basin Only in the western margin of the Sichuan Basin the peak ground acceleration is larger than 015 g

which the total natural gas reserves are 1509268 times 108m3accounting for 876 of the total proven OGIP in the basin(Table 7)

33 Unmineable Coal Seams The CBM geological reservesin the Sichuan Basin amount to 347140 times 108m3 in Sichuanprovince and Chongqing city 508457 times 108m3 in SouthernSichuan province and Northern Guizhou province respec-tively from 1000 to 2000meters depth [39] Among these thecoalfields in Southern Sichuan province are the most abun-dant accounting for 82 of the provincersquos total resources

34 Deep Saline Aquifers Comparedwith oil fields gas fieldsand unmineable coal seams the analysis of geological condi-tions for saline aquifers CO2 geological storage is muchmorecomplex The CO2 geological storage candidate prospectivearea for deep saline aquifers CO2 storage was selected fromthe map projection on the ground of all potential under-ground CO2 reservoirs In addition the hydrodynamic andgeological safety conditions must be studied to delineate thecandidate prospective areas

341 Candidate Prospective Area Delineation Standards Asmentioned above this report presents the delineation stan-dards of the CO2 geological storage candidate prospective

Table 8 Veto over key factors of CO2 geological storage candidateprospective areas delineation

Key factors VetoReservoir conditions

Layer thickness lt10mPorosity lt5Permeability lt1mD

Hydrogeological conditionsFormation water salinity lt3 gLGroundwater hydrodynamic condition Groundwater zone

Geological safety conditionsActive faults lt25 kmPeak ground acceleration ge040 g

areas shown in Table 8 Further potential and suitabilityassessments can be carried out for target area selection

342 Vertical Reservoir Cap Combination and CandidateProspective Areas Distribution The reservoirs for deep salineaquifer CO2 storage consist of the Permian the lower Triassiccarbonates and upper Triassic and Jurassic clastic reservoirs(Figure 5)The reservoir space includes carbonate karst poresand cracks and clastic pores and cracks Overall all reservoirs

10 Geofluids

Geochronology

Series Formation

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Penglaizhen

Suining

Shaximiao

Qianfoya

Ziliujing

Six

Xiaotangzi

Marsquoantang

Tianjingshan

Leikoupo

Changxing

Longtan

Maokou

Qixia

LiangshanCarbon-iferous

Permian

Upper

Stata

Middle

Lower

Upper

Upper

Middle

Middle

Lower

Lower

Five

Four

Three

Two

One

Four

Three

Two

One

Five

Four

Three

Two

One

Litho-histogram

D

depr

essio

nrift

Sandstone

Mudstone

Mud sandstone

Limestone

Dolomite

Reservoir

Caprock

Thick-ness(m)

Poro-sity()

Perme-ability(mD)

Coverage

Local

Regional

Regional

Regional

1244

5Local

Average

5Local

AverageLocal

10 5Local

10 5Local

Porefracture

Reservoirspace

fracture

Porefracture

Porefracture

Dissolved porefracture

Fracture-cave

Fracture-cave

Porefracture

525Average

605AverageLocal

Average

Dissolved pore

Dissolved pore

Rese

rvoi

r

Capr

ock

Tect

onic

mov

emen

tBa

sinev

olut

ion

Mid

dle Y

ansh

an

Fore

land

Late

Indo

sinia

n

Intr

acra

toni

c

ongw

u

Pore

001ndash10

gt1

gt200

gt1

gt1gt6

gt7

gt1

gt1

gt8gt10

gt1

gt1

gt1725

4ndash10

6ndash80

25ndash70

25ndash30

100ndash200

100ndash200

0ndash300

Jialin

gjia

ngFe

ixia

ngua

nXu

jiahe

Figure 5 CO2 geological storage vertical reservoir cap combination in the Sichuan Basin There are nine sets of reservoirs in the SichuanBasin and the section four of Xujiahe group is the primary reservoir with large thickness and area which almost cover the whole basin

Geofluids 11

Table 9 Storage potential of CO2 geological storage in depleted oil fields

Tectonic unit OOIP108 t Oil density(kgm3) 119861 (mdash) Reservoir

pressureMpaOil

temperature∘C120588CO2

(kgm3)119864oil 119866CO2

108 t

Central Sichuan flatstructure area 058 850 118 2126 6442 71263 075 057

Northern Sichuan flatstructure area 017 850 118 2126 6442 71263 075 017

Table 10 CO2-EOR geological storage potential in the Sichuan Basin

Tectonic unit API EXTRA () 119875LCO2() 119875HCO2

() 119864oil 119866CO2-EOR108 t

Central Sichuan flatstructure area 3497 1046 33 66 075 016

Northern Sichuan flatstructure area 3497 1046 33 66 075 005

in the Sichuan Basin have poor physical properties withultra-low porosity and low permeability Comparing withthe natural gas fields in the Sichuan Basin these reservoirsfor CO2 storage have better caprock conditions too Forexample the extensive deposits of gypsum rocks in theLeikoupo phase and the widely developed dark mudstone inthe Lower Jurassic can provide good sealing conditions forthe underlying reservoirs

(1) The Permian The reef flat facies on the top of Qixiagroup form a good reservoir through dolomitization withfavorable reservoir conditions (P2q) [40] Part of them formthe natural gas reservoirs with a thickness of approximately10m Similar to the Qixia group the Maokou group (P2m)is a fracture-cave type of reservoir Changxing group (P3c)reservoirs are pore type and fracture-pore type The porosityis generally 203ndash1585 with an average value of 525 thepermeability is less than 1000mD with an average value of605mD The reservoir thickness is large with a monolayerthickness of 05ndash5m and a single well cumulative thicknessof 25ndash70m [41]

(2) The Triassic The Feixianguan group (T1f ) is similar tothe Changxing groupThe quality and distribution of the reefbeach reservoir are mainly controlled by sedimentary faciesand diagenesis The evaporative platform oolitic dolomitereservoir is mainly distributed in Northeast Sichuan witha monolayer thickness of 15ndash15m and total thickness of20ndash50m The porosity ranges from 2 to 268 on theaverage of 829 and the permeability is less than 1160mDwith an average value of 5973mD The porosity of the openplatform edge oolitic dolomite reservoir is 205ndash2262 onthe average of 842 and the permeability is less than 410mDwith an average value of 1725mD The reservoir monolayerthickness is generally 05ndash6m and the total thickness is10ndash45m typically

The favorable Jialingjiang reservoir facies are the platforminterior shoal and the platform margin shoal facies Forexample section five of Jialingjiang reservoirs consists oflimestone and dolomite with a thickness of 25ndash30m ofwhich approximately 60 is the porosity layer and the

average of the porosity is 5 with the highest value reaching18

The sandstone aquifers in section two section four andsection six of Xujiahe formation could be reservoirs for CO2geological storage composed of residual intergranular poreintergranular dissolved pore and fracture The sand ratioof the sandstones is greater than 70 in 80 generally Inaddition the porosity of section four is higher than sectiontwo and section six usually between 5ndash10 while theporosity of sandstones in section two and section is less than7 generally

Figure 6 shows the candidate prospective areas in theSichuan Basin in the Sichuan Basin for deep saline aquiferCO2 storage based on geology study

4 Results

41 Potential

411 Depleted Oil Fields CO2 Storage and CO2-EOR Theprimary CO2-EOR prospective areas in the Sichuan Basinare located in the flat tectonic area in Central and NorthernSichuan Basin As shown in Tables 9 and 10 the CO2geological storage potential of storage in depleted oil fieldsis only 074 times 108 t while the storage potential is about 021 times108 t by using CO2-EOR technology

412 Depleted Gas Fields CO2 Storage and CO2-EGR TheCO2 geological storage potential of depleted gas fields is 5373times 108 t By using CO2-EGR technology the Sichuan Basin gasfields could achieve CO2 geological storage of 3385 times 108 tAmong that 27 large and medium gas fields have the greatestpotential with the possibility of achieving a CO2 geologicalstorage capacity of 4239 times 108 t in depleted gas fields whilethe storage potential is about 2670 times 108 t by using CO2-EGRtechnology

413 Unmineable Coal Seams CO2 Storage and CO2-ECBMThe Sichuan Basin has abundant coal bedmethane resourcesAs shown in Table 11 the total CO2 geological storage

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

Geofluids 9

gt015 g

gt015

g

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Seismic peak ground acceleration First-order tectonic units

Second-order tectonic unitsHistorical earthquakes (M 6ndash69)

010 gndash015g

lt005 g

lt005 g

lt005 g

lt005 g

gndash010g005

0 50 100(km)

Figure 4 Seismic peak ground acceleration and large historical earthquakes in the Sichuan Basin The peak ground acceleration is less than010 g in most parts of the Sichuan Basin Only in the western margin of the Sichuan Basin the peak ground acceleration is larger than 015 g

which the total natural gas reserves are 1509268 times 108m3accounting for 876 of the total proven OGIP in the basin(Table 7)

33 Unmineable Coal Seams The CBM geological reservesin the Sichuan Basin amount to 347140 times 108m3 in Sichuanprovince and Chongqing city 508457 times 108m3 in SouthernSichuan province and Northern Guizhou province respec-tively from 1000 to 2000meters depth [39] Among these thecoalfields in Southern Sichuan province are the most abun-dant accounting for 82 of the provincersquos total resources

34 Deep Saline Aquifers Comparedwith oil fields gas fieldsand unmineable coal seams the analysis of geological condi-tions for saline aquifers CO2 geological storage is muchmorecomplex The CO2 geological storage candidate prospectivearea for deep saline aquifers CO2 storage was selected fromthe map projection on the ground of all potential under-ground CO2 reservoirs In addition the hydrodynamic andgeological safety conditions must be studied to delineate thecandidate prospective areas

341 Candidate Prospective Area Delineation Standards Asmentioned above this report presents the delineation stan-dards of the CO2 geological storage candidate prospective

Table 8 Veto over key factors of CO2 geological storage candidateprospective areas delineation

Key factors VetoReservoir conditions

Layer thickness lt10mPorosity lt5Permeability lt1mD

Hydrogeological conditionsFormation water salinity lt3 gLGroundwater hydrodynamic condition Groundwater zone

Geological safety conditionsActive faults lt25 kmPeak ground acceleration ge040 g

areas shown in Table 8 Further potential and suitabilityassessments can be carried out for target area selection

342 Vertical Reservoir Cap Combination and CandidateProspective Areas Distribution The reservoirs for deep salineaquifer CO2 storage consist of the Permian the lower Triassiccarbonates and upper Triassic and Jurassic clastic reservoirs(Figure 5)The reservoir space includes carbonate karst poresand cracks and clastic pores and cracks Overall all reservoirs

10 Geofluids

Geochronology

Series Formation

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Penglaizhen

Suining

Shaximiao

Qianfoya

Ziliujing

Six

Xiaotangzi

Marsquoantang

Tianjingshan

Leikoupo

Changxing

Longtan

Maokou

Qixia

LiangshanCarbon-iferous

Permian

Upper

Stata

Middle

Lower

Upper

Upper

Middle

Middle

Lower

Lower

Five

Four

Three

Two

One

Four

Three

Two

One

Five

Four

Three

Two

One

Litho-histogram

D

depr

essio

nrift

Sandstone

Mudstone

Mud sandstone

Limestone

Dolomite

Reservoir

Caprock

Thick-ness(m)

Poro-sity()

Perme-ability(mD)

Coverage

Local

Regional

Regional

Regional

1244

5Local

Average

5Local

AverageLocal

10 5Local

10 5Local

Porefracture

Reservoirspace

fracture

Porefracture

Porefracture

Dissolved porefracture

Fracture-cave

Fracture-cave

Porefracture

525Average

605AverageLocal

Average

Dissolved pore

Dissolved pore

Rese

rvoi

r

Capr

ock

Tect

onic

mov

emen

tBa

sinev

olut

ion

Mid

dle Y

ansh

an

Fore

land

Late

Indo

sinia

n

Intr

acra

toni

c

ongw

u

Pore

001ndash10

gt1

gt200

gt1

gt1gt6

gt7

gt1

gt1

gt8gt10

gt1

gt1

gt1725

4ndash10

6ndash80

25ndash70

25ndash30

100ndash200

100ndash200

0ndash300

Jialin

gjia

ngFe

ixia

ngua

nXu

jiahe

Figure 5 CO2 geological storage vertical reservoir cap combination in the Sichuan Basin There are nine sets of reservoirs in the SichuanBasin and the section four of Xujiahe group is the primary reservoir with large thickness and area which almost cover the whole basin

Geofluids 11

Table 9 Storage potential of CO2 geological storage in depleted oil fields

Tectonic unit OOIP108 t Oil density(kgm3) 119861 (mdash) Reservoir

pressureMpaOil

temperature∘C120588CO2

(kgm3)119864oil 119866CO2

108 t

Central Sichuan flatstructure area 058 850 118 2126 6442 71263 075 057

Northern Sichuan flatstructure area 017 850 118 2126 6442 71263 075 017

Table 10 CO2-EOR geological storage potential in the Sichuan Basin

Tectonic unit API EXTRA () 119875LCO2() 119875HCO2

() 119864oil 119866CO2-EOR108 t

Central Sichuan flatstructure area 3497 1046 33 66 075 016

Northern Sichuan flatstructure area 3497 1046 33 66 075 005

in the Sichuan Basin have poor physical properties withultra-low porosity and low permeability Comparing withthe natural gas fields in the Sichuan Basin these reservoirsfor CO2 storage have better caprock conditions too Forexample the extensive deposits of gypsum rocks in theLeikoupo phase and the widely developed dark mudstone inthe Lower Jurassic can provide good sealing conditions forthe underlying reservoirs

(1) The Permian The reef flat facies on the top of Qixiagroup form a good reservoir through dolomitization withfavorable reservoir conditions (P2q) [40] Part of them formthe natural gas reservoirs with a thickness of approximately10m Similar to the Qixia group the Maokou group (P2m)is a fracture-cave type of reservoir Changxing group (P3c)reservoirs are pore type and fracture-pore type The porosityis generally 203ndash1585 with an average value of 525 thepermeability is less than 1000mD with an average value of605mD The reservoir thickness is large with a monolayerthickness of 05ndash5m and a single well cumulative thicknessof 25ndash70m [41]

(2) The Triassic The Feixianguan group (T1f ) is similar tothe Changxing groupThe quality and distribution of the reefbeach reservoir are mainly controlled by sedimentary faciesand diagenesis The evaporative platform oolitic dolomitereservoir is mainly distributed in Northeast Sichuan witha monolayer thickness of 15ndash15m and total thickness of20ndash50m The porosity ranges from 2 to 268 on theaverage of 829 and the permeability is less than 1160mDwith an average value of 5973mD The porosity of the openplatform edge oolitic dolomite reservoir is 205ndash2262 onthe average of 842 and the permeability is less than 410mDwith an average value of 1725mD The reservoir monolayerthickness is generally 05ndash6m and the total thickness is10ndash45m typically

The favorable Jialingjiang reservoir facies are the platforminterior shoal and the platform margin shoal facies Forexample section five of Jialingjiang reservoirs consists oflimestone and dolomite with a thickness of 25ndash30m ofwhich approximately 60 is the porosity layer and the

average of the porosity is 5 with the highest value reaching18

The sandstone aquifers in section two section four andsection six of Xujiahe formation could be reservoirs for CO2geological storage composed of residual intergranular poreintergranular dissolved pore and fracture The sand ratioof the sandstones is greater than 70 in 80 generally Inaddition the porosity of section four is higher than sectiontwo and section six usually between 5ndash10 while theporosity of sandstones in section two and section is less than7 generally

Figure 6 shows the candidate prospective areas in theSichuan Basin in the Sichuan Basin for deep saline aquiferCO2 storage based on geology study

4 Results

41 Potential

411 Depleted Oil Fields CO2 Storage and CO2-EOR Theprimary CO2-EOR prospective areas in the Sichuan Basinare located in the flat tectonic area in Central and NorthernSichuan Basin As shown in Tables 9 and 10 the CO2geological storage potential of storage in depleted oil fieldsis only 074 times 108 t while the storage potential is about 021 times108 t by using CO2-EOR technology

412 Depleted Gas Fields CO2 Storage and CO2-EGR TheCO2 geological storage potential of depleted gas fields is 5373times 108 t By using CO2-EGR technology the Sichuan Basin gasfields could achieve CO2 geological storage of 3385 times 108 tAmong that 27 large and medium gas fields have the greatestpotential with the possibility of achieving a CO2 geologicalstorage capacity of 4239 times 108 t in depleted gas fields whilethe storage potential is about 2670 times 108 t by using CO2-EGRtechnology

413 Unmineable Coal Seams CO2 Storage and CO2-ECBMThe Sichuan Basin has abundant coal bedmethane resourcesAs shown in Table 11 the total CO2 geological storage

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

10 Geofluids

Geochronology

Series Formation

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Penglaizhen

Suining

Shaximiao

Qianfoya

Ziliujing

Six

Xiaotangzi

Marsquoantang

Tianjingshan

Leikoupo

Changxing

Longtan

Maokou

Qixia

LiangshanCarbon-iferous

Permian

Upper

Stata

Middle

Lower

Upper

Upper

Middle

Middle

Lower

Lower

Five

Four

Three

Two

One

Four

Three

Two

One

Five

Four

Three

Two

One

Litho-histogram

D

depr

essio

nrift

Sandstone

Mudstone

Mud sandstone

Limestone

Dolomite

Reservoir

Caprock

Thick-ness(m)

Poro-sity()

Perme-ability(mD)

Coverage

Local

Regional

Regional

Regional

1244

5Local

Average

5Local

AverageLocal

10 5Local

10 5Local

Porefracture

Reservoirspace

fracture

Porefracture

Porefracture

Dissolved porefracture

Fracture-cave

Fracture-cave

Porefracture

525Average

605AverageLocal

Average

Dissolved pore

Dissolved pore

Rese

rvoi

r

Capr

ock

Tect

onic

mov

emen

tBa

sinev

olut

ion

Mid

dle Y

ansh

an

Fore

land

Late

Indo

sinia

n

Intr

acra

toni

c

ongw

u

Pore

001ndash10

gt1

gt200

gt1

gt1gt6

gt7

gt1

gt1

gt8gt10

gt1

gt1

gt1725

4ndash10

6ndash80

25ndash70

25ndash30

100ndash200

100ndash200

0ndash300

Jialin

gjia

ngFe

ixia

ngua

nXu

jiahe

Figure 5 CO2 geological storage vertical reservoir cap combination in the Sichuan Basin There are nine sets of reservoirs in the SichuanBasin and the section four of Xujiahe group is the primary reservoir with large thickness and area which almost cover the whole basin

Geofluids 11

Table 9 Storage potential of CO2 geological storage in depleted oil fields

Tectonic unit OOIP108 t Oil density(kgm3) 119861 (mdash) Reservoir

pressureMpaOil

temperature∘C120588CO2

(kgm3)119864oil 119866CO2

108 t

Central Sichuan flatstructure area 058 850 118 2126 6442 71263 075 057

Northern Sichuan flatstructure area 017 850 118 2126 6442 71263 075 017

Table 10 CO2-EOR geological storage potential in the Sichuan Basin

Tectonic unit API EXTRA () 119875LCO2() 119875HCO2

() 119864oil 119866CO2-EOR108 t

Central Sichuan flatstructure area 3497 1046 33 66 075 016

Northern Sichuan flatstructure area 3497 1046 33 66 075 005

in the Sichuan Basin have poor physical properties withultra-low porosity and low permeability Comparing withthe natural gas fields in the Sichuan Basin these reservoirsfor CO2 storage have better caprock conditions too Forexample the extensive deposits of gypsum rocks in theLeikoupo phase and the widely developed dark mudstone inthe Lower Jurassic can provide good sealing conditions forthe underlying reservoirs

(1) The Permian The reef flat facies on the top of Qixiagroup form a good reservoir through dolomitization withfavorable reservoir conditions (P2q) [40] Part of them formthe natural gas reservoirs with a thickness of approximately10m Similar to the Qixia group the Maokou group (P2m)is a fracture-cave type of reservoir Changxing group (P3c)reservoirs are pore type and fracture-pore type The porosityis generally 203ndash1585 with an average value of 525 thepermeability is less than 1000mD with an average value of605mD The reservoir thickness is large with a monolayerthickness of 05ndash5m and a single well cumulative thicknessof 25ndash70m [41]

(2) The Triassic The Feixianguan group (T1f ) is similar tothe Changxing groupThe quality and distribution of the reefbeach reservoir are mainly controlled by sedimentary faciesand diagenesis The evaporative platform oolitic dolomitereservoir is mainly distributed in Northeast Sichuan witha monolayer thickness of 15ndash15m and total thickness of20ndash50m The porosity ranges from 2 to 268 on theaverage of 829 and the permeability is less than 1160mDwith an average value of 5973mD The porosity of the openplatform edge oolitic dolomite reservoir is 205ndash2262 onthe average of 842 and the permeability is less than 410mDwith an average value of 1725mD The reservoir monolayerthickness is generally 05ndash6m and the total thickness is10ndash45m typically

The favorable Jialingjiang reservoir facies are the platforminterior shoal and the platform margin shoal facies Forexample section five of Jialingjiang reservoirs consists oflimestone and dolomite with a thickness of 25ndash30m ofwhich approximately 60 is the porosity layer and the

average of the porosity is 5 with the highest value reaching18

The sandstone aquifers in section two section four andsection six of Xujiahe formation could be reservoirs for CO2geological storage composed of residual intergranular poreintergranular dissolved pore and fracture The sand ratioof the sandstones is greater than 70 in 80 generally Inaddition the porosity of section four is higher than sectiontwo and section six usually between 5ndash10 while theporosity of sandstones in section two and section is less than7 generally

Figure 6 shows the candidate prospective areas in theSichuan Basin in the Sichuan Basin for deep saline aquiferCO2 storage based on geology study

4 Results

41 Potential

411 Depleted Oil Fields CO2 Storage and CO2-EOR Theprimary CO2-EOR prospective areas in the Sichuan Basinare located in the flat tectonic area in Central and NorthernSichuan Basin As shown in Tables 9 and 10 the CO2geological storage potential of storage in depleted oil fieldsis only 074 times 108 t while the storage potential is about 021 times108 t by using CO2-EOR technology

412 Depleted Gas Fields CO2 Storage and CO2-EGR TheCO2 geological storage potential of depleted gas fields is 5373times 108 t By using CO2-EGR technology the Sichuan Basin gasfields could achieve CO2 geological storage of 3385 times 108 tAmong that 27 large and medium gas fields have the greatestpotential with the possibility of achieving a CO2 geologicalstorage capacity of 4239 times 108 t in depleted gas fields whilethe storage potential is about 2670 times 108 t by using CO2-EGRtechnology

413 Unmineable Coal Seams CO2 Storage and CO2-ECBMThe Sichuan Basin has abundant coal bedmethane resourcesAs shown in Table 11 the total CO2 geological storage

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

Geofluids 11

Table 9 Storage potential of CO2 geological storage in depleted oil fields

Tectonic unit OOIP108 t Oil density(kgm3) 119861 (mdash) Reservoir

pressureMpaOil

temperature∘C120588CO2

(kgm3)119864oil 119866CO2

108 t

Central Sichuan flatstructure area 058 850 118 2126 6442 71263 075 057

Northern Sichuan flatstructure area 017 850 118 2126 6442 71263 075 017

Table 10 CO2-EOR geological storage potential in the Sichuan Basin

Tectonic unit API EXTRA () 119875LCO2() 119875HCO2

() 119864oil 119866CO2-EOR108 t

Central Sichuan flatstructure area 3497 1046 33 66 075 016

Northern Sichuan flatstructure area 3497 1046 33 66 075 005

in the Sichuan Basin have poor physical properties withultra-low porosity and low permeability Comparing withthe natural gas fields in the Sichuan Basin these reservoirsfor CO2 storage have better caprock conditions too Forexample the extensive deposits of gypsum rocks in theLeikoupo phase and the widely developed dark mudstone inthe Lower Jurassic can provide good sealing conditions forthe underlying reservoirs

(1) The Permian The reef flat facies on the top of Qixiagroup form a good reservoir through dolomitization withfavorable reservoir conditions (P2q) [40] Part of them formthe natural gas reservoirs with a thickness of approximately10m Similar to the Qixia group the Maokou group (P2m)is a fracture-cave type of reservoir Changxing group (P3c)reservoirs are pore type and fracture-pore type The porosityis generally 203ndash1585 with an average value of 525 thepermeability is less than 1000mD with an average value of605mD The reservoir thickness is large with a monolayerthickness of 05ndash5m and a single well cumulative thicknessof 25ndash70m [41]

(2) The Triassic The Feixianguan group (T1f ) is similar tothe Changxing groupThe quality and distribution of the reefbeach reservoir are mainly controlled by sedimentary faciesand diagenesis The evaporative platform oolitic dolomitereservoir is mainly distributed in Northeast Sichuan witha monolayer thickness of 15ndash15m and total thickness of20ndash50m The porosity ranges from 2 to 268 on theaverage of 829 and the permeability is less than 1160mDwith an average value of 5973mD The porosity of the openplatform edge oolitic dolomite reservoir is 205ndash2262 onthe average of 842 and the permeability is less than 410mDwith an average value of 1725mD The reservoir monolayerthickness is generally 05ndash6m and the total thickness is10ndash45m typically

The favorable Jialingjiang reservoir facies are the platforminterior shoal and the platform margin shoal facies Forexample section five of Jialingjiang reservoirs consists oflimestone and dolomite with a thickness of 25ndash30m ofwhich approximately 60 is the porosity layer and the

average of the porosity is 5 with the highest value reaching18

The sandstone aquifers in section two section four andsection six of Xujiahe formation could be reservoirs for CO2geological storage composed of residual intergranular poreintergranular dissolved pore and fracture The sand ratioof the sandstones is greater than 70 in 80 generally Inaddition the porosity of section four is higher than sectiontwo and section six usually between 5ndash10 while theporosity of sandstones in section two and section is less than7 generally

Figure 6 shows the candidate prospective areas in theSichuan Basin in the Sichuan Basin for deep saline aquiferCO2 storage based on geology study

4 Results

41 Potential

411 Depleted Oil Fields CO2 Storage and CO2-EOR Theprimary CO2-EOR prospective areas in the Sichuan Basinare located in the flat tectonic area in Central and NorthernSichuan Basin As shown in Tables 9 and 10 the CO2geological storage potential of storage in depleted oil fieldsis only 074 times 108 t while the storage potential is about 021 times108 t by using CO2-EOR technology

412 Depleted Gas Fields CO2 Storage and CO2-EGR TheCO2 geological storage potential of depleted gas fields is 5373times 108 t By using CO2-EGR technology the Sichuan Basin gasfields could achieve CO2 geological storage of 3385 times 108 tAmong that 27 large and medium gas fields have the greatestpotential with the possibility of achieving a CO2 geologicalstorage capacity of 4239 times 108 t in depleted gas fields whilethe storage potential is about 2670 times 108 t by using CO2-EGRtechnology

413 Unmineable Coal Seams CO2 Storage and CO2-ECBMThe Sichuan Basin has abundant coal bedmethane resourcesAs shown in Table 11 the total CO2 geological storage

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

12 Geofluids

Prospective areas

First-order tectonic units

Second-order tectonic units

Chengdu

Leshan

Zigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

II

I

VI

VII

III

IV

V

VIII

III

Figure 6 Candidate prospective areas in the Sichuan Basin There are eight candidate prospective areas in the Sichuan Basin for deepsaline aquifer CO2 storage which cover more than 5 times 104 km2 and mainly locate in Central Sichuan Basin (districts IIndashV) Only districtI is in Northwestern Sichuan The candidate prospective areas (districts VIndashVIII) in Eastern Sichuan are relatively small due to the effects offormation depth geological safety and hydrogeological conditions

Table 11 Storage potential of CO2 in unmineable coal seams and CO2-ECBM in the Sichuan Basin

Area 119866CBM108m3 Types of coal 119877CO2CH4119862 120588CO2std (kgm

3) 119866CO2108 t 119866CO2-ECBM10

8 tSouthern Sichuan andNorthern Guizhou 508457 Mainly anthracite 1 050 1977 372 186

Sichuan andChongqing 347140 Mainly coking coal

and lean coal 1 050 1977 254 127

potential of unmineable coal seams can vary in the rangefrom 355 times 108 t to 812 times 108 t (626 times 108 t on the average)while the storage potential of CO2-ECBM technology is halfof the unmineable coal seams CO2 geological storage

However the coal bed methane in the Sichuan Basinproposed by Ministry of Land and Resources (MLR) is justthe theoretical geological reserves in place but not provenreserves so the reliability of potential of unmineable coalseams and CO2-ECBM is much lower than depleted oil andgas fields CO2 storage and CO2-EOR and CO2-EGR

414 Deep Saline Aquifers CO2 Storage or CO2-EWR Thetotal CO2 geological storage potential in deep saline aquifers

varies in the range of 7781 times 108 t to 26208 times 108 t (15420times 108 t on the average) However the main CO2 geologicalreservoirs are sections two four and six of Xujiahe formationwith the storage potential of 7198 times 108 t to 24595 times 108 t(14398 times 108 t on the average) that is approximately 9337of the total storage potential

According to the statistics of the structural positionthe total expected storage potential in Central Sichuan isthe largest reaching 8926 times 108 t on the average Thetotal expected storage potentials in Western Sichuan andEastern Sichuan are 4568 times 108 t and 1927 times 108 t on theaverage respectively The potential per unit area is shown inFigure 7

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

Geofluids 13

Chengdu

I

II

III

VI

VII

VII

V

IV

LeshanZigong

Neijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

0 50 100(km)

Pote

ntia

l104

tkm

2

0

50

100

150

Figure 7 Storage potential per unit area for each prospective area Due to the large stratigraphic thickness and many reservoir layers thestorage potential per unit area in most depressions in Northwestern Sichuan is quite large with the largest up to 140 times 104 tkm2 at P50probability level The storage potential per unit area in Central Sichuan is generally greater than 50 times 104 tkm2 at P50 probability level

Table 12 Geological suitability assessment information of the main reservoir distribution area (within section four of Xujiahe formation)

Level one index Level two index Level three indexDistribution informationof the main reservoir in

Xujiahe section 4

Geological informationoutside of Xujiahe

section 4 distribution

Reservoir conditions andstorage potential

Reservoir geologicalcharacteristics

Lithology Clastic Mix of clastic andcarbonate

Thicknessm ge80 lt30Sedimentary facies River delta Beach bar reefAverage porosity GIS partition processing lt10

AveragepermeabilitymD lt10 lt10

Storage potential Storage potential perunit area (104 tkm2) GIS partition processing GIS partition processing

Geological safety

Cap geologicalcharacteristics

Lithology Argillite ArgilliteThicknessm ge100 ge100

Main cap depth 1000ndash2700 1000ndash2700Buffer cap above main

cap Multiple sets Multiple sets

Hydrodynamicconditions

Hydrodynamicconditions GIS partition processing GIS partition processing

Seismic activityPeak groundacceleration GIS partition processing GIS partition processing

Fracture development GIS partition processing GIS partition processingThe main reservoir is the section four of Xujiahe formation and the main cap is the lower Jurassic strata The GIS partition processing must be carried outseparately for the prospective areas within and outside of section four of Xujiahe formation The geological information outside of section four of Xujiaheformation is from the best value of other eight reservoirs

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

14 Geofluids

Table 13 Storage potential results in this paper compared with studies before

CCUS Study scales Authors Results before (108 t) Basic dataCO2 geological utilization

CO2-EORNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 021

CO2-EGRNational ACCA 21 2014

MLR 2010National Wei 2015Target This paper 2670

CO2-ECBMNational ACCA 21 2014

MLR 2009National Wei 2015Target This paper 313

CO2 geological storage

Depleted oil fields

National Zhang 2005Basin Li 2009 020 Li 2002

National ACCA 21 2014

MLR 2010Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 074

Depleted gas fields

National Zhang 2005National Liu 2006 1014 900sim3500m Recoverable reserves [25]Basin Li 2009 1050

MLR 2010National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 4239

Unmineable coal seams

National Zhang 2005National ACCA 21 2014

MLR 2009Basin Guo 2014 UnpublishedNational Wei 2015Target This paper 626

Deep saline aquifers

National Zhang 2005National Li 2006 6407National Li 2009National ACCA 21 2014Basin Guo 2014 Unpublished

National Wei 2015Target This paper 15420 Further geological study

42 Target Areas for Deep Saline Aquifers CO2 Storage

421 Data On the basis of systematic analysis of thedeep saline aquifer CO2 geological storage cap through thegeological suitability evaluation index system the superim-posed multisource information evaluation was successivelycarried out using ArcGIS software The basic information isshown in Table 12 As mentioned in Section 342 the mainreservoir in the Sichuan Basin is the section four of Xujiaheformation

422 Target Areas As shown in Figure 8 most prospectiveareas are suitable for CO2 geological storage The suitableareas could be used as the target areas for CO2 geological

storage By further ground suitability evaluation and socialeconomic surveys some project sites can be identified fromthose target areas for large-scale saline aquifers CO2 geologi-cal storage

5 Discussion and Conclusions

51 Discussion The purpose of this paper is not only toevaluate the mesoscale potential of different CCUS tech-nologies but also select the suitable target areas for earlydemonstration in the Sichuan Basin On the basis of geologystudy the CO2 storage potential of CO2-EOR CO2-EGRCO2-ECBM and saline aquifer CO2 storage technologieswas first evaluated comprehensively Compared with the

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

Geofluids 15

Chengdu

Leshan

ZigongNeijiang

Suining

Chongqing

LuzhouYibin

Guangyuan

Mianyang

Deyang

Nanchong

Guangrsquoan

Scores of suitability7

Suita

ble

5

3

4

6

0 50 100(km)

Less

suita

ble

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

103∘09984000998400998400E 104

∘09984000998400998400E 105

∘09984000998400998400E 106

∘09984000998400998400E 107

∘09984000998400998400E 108

∘09984000998400998400E 109

∘09984000998400998400E

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

32∘09984000998400998400N

31∘09984000998400998400N

30∘09984000998400998400N

29∘09984000998400998400N

28∘09984000998400998400N

Figure 8 Assessment results of CO2 geological storage suitability (suitable area is the ldquotarget areardquo) Most prospective areas in the SichuanBasin are suitable for CO2 geological storage which could be the ldquotarget areasrdquo for CO2 geological storageThemain reservoirs in the CentralSichuan Basin are sections two four and six of Xujiahe formation with large thickness and good physical properties They are far from thebasin boundary faults with weak hydrodynamic and good geological safety conditions

similar studies before the study scale in this paper is moredetailed especially for CO2 storage in deep saline aquiferswhich is based on further geological study of reservoirsseals hydrogeology and geological safety The basic datafor potential assessment are from MLR PetroChina andother authorities thus the potential results are more credibleand more in accordance with geology Table 13 shows thestorage potential results in this paper compared with studiesbefore

52 Conclusions Taking the low technical application levelsof CO2-EWR andCO2-EGR into account it is recommendedthat deep saline aquifers and depleted gas fields CO2 geologi-cal storage in the Sichuan Basin could be early demonstratedespecially that of the latter because of excellent traps richgeological data and well-run infrastructures

521 Deep Saline Aquifers CO2 Geological Storage For deepsaline aquifers CO2 geological storage based on the con-sideration of deep saline aquifer CO2 geological storagemechanism and geology of the Sichuan Basin this paperproposes the study order of ldquoprospective areasrdquo to ldquotargetareasrdquo and a newGIS superimposedmultisource informationevaluation method of geological suitability for target selec-tion The index system of geological suitability assessmentfor target selection is appropriate for multiple tectonicsfacies and reservoirs to evaluate the suitability of prospective

areas to select suitable target areas The GIS superimposedmultisource information evaluation results show that mostareas are suitable for CO2 geological storage and only somelocal peripheral areas are not suitable for CO2 geologicalstorage The areas selected through geological suitabilityassessment can be used as target areas for CO2 geologicalstorage

The geology in Central Sichuan provides the best con-ditions and the storage potential per unit area in CentralSichuan is generally greater than 50 times 104 tkm2 at P50probability level with Xujiahe group is the main reservoirHowever deep saline aquifers CO2 geological storage couldonly be used in the future due to its lack of other economicbenefits high investment and multiple barriers in the shortterm

522 Depleted Gas Fields CO2 Geological Storage In themesoscale gas fields under exploration or exploitation canbe used as target areas for depleted gas fields CO2 geologicalstorage The MLR has announced that there are 125 gas fieldsin the Sichuan Basin and 27medium to large-sized confirmedgas fields among them There are many gas reservoirs ortraps becomes depleted which provide a great chance forearly demonstration first for the CO2 resources located in theSichuan Basin Even in the long run the depleted gas fieldscould be the main reservoirs for CO2 geological storage inthe Sichuan Basin

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

16 Geofluids

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors gratefully acknowledge the financial support ofthe project of China National Natural Science FoundationldquoMechanism of the Different CO2 Distribution Saturationin Saline Aquifers Based on High Reliable Modeling (Grantno 41602270)rdquo the China Clean Development MechanismFund project of National Development and Reform Com-mission ldquoResearch on the Guidelines for the Management ofUnderground Space Development for CO2 Geological Storage(Grant no 2014088)rdquo the geological survey project of ChinaGeological Survey ldquoComprehensive Geological Survey of CO2Geological Storage in the Junggar and Other Basins (Grantno 121201012000150010)rdquo the UK-China Strategic ProsperityFund (CPF) project of British Embassy Beijing ldquoIdentifyingCO2 Storage Opportunities in Depleted Gas Reservoirs JointUK-China Studies in Sichuan Basinrdquo and ldquoResearch on Assess-ment of CO2 GeologicalUtilization Storage Potential andEarlyDemonstration Opportunity in the Sichuan Basinrdquo the China-Australia Geological Storage of CO2 project of GeoscienceAustralia and the Administrative Center for Chinarsquos Agenda21 The authors also gratefully acknowledge the support ofInstitute of Rock and Soil Mechanics Chinese Academy ofSciences and Chongqing University

References

[1] IPCC ldquoIPCC Fifth Assessment Report Working Group IReport rdquoClimateChange 2013ThePhysical Science Basisrdquo TechRep 2013 httpwwwipccchreportar5wg1

[2] B Bai X Li Y Liu and Y Zhang ldquoPreliminary study onCO2 industrial point sources and their distribution in ChinardquoChinese Journal of Rock Mechanics and Engineering vol 25 no1 pp 2918ndash2923 2006

[3] ACCA21 (The Administrative Centre for Chinarsquos Agenda 21)ldquoThe 3rd Report on National Assessment of Climate Change- Special Report on CO2 Utilization Technologiesrdquo Tech RepScience Press Ltd Beijing China 2014

[4] CSLF ldquoPhase I Final Report from the Task Force for Reviewand Identification of Standards for CO2 Storage Capacity Mea-surement Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form Augustrdquo Tech Rep 2005 ed p 22 2005

[5] CSLF ldquoEstimation of CO2storage capacity in geological media(Phase) Prepared by the task force on CO2 storage capacityestimation for the technical group of the Carbon SequestrationLeadership Form 15 Junerdquo Tech Rep 2007 ed p 24 2007

[6] CSLF (Carbon Sequestration Leadership Forum) Task Force forReview and Identification of Standards for CO2 Storage CapacityEstimation 2010 httpwwwcslforumorg

[7] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2006 httpwwwnetldoegovtechnologiescar-bonseqrefshelfatlas

[8] DOE-NETL Carbon Sequestration Atlas of the United Statesand Canada 2nd edition 2008 httpwwwnetldoegovtech-nologiescarbon seqrefshelfatlas

[9] DOE-NETL Carbon Sequestration Atlas of the United Stateand Canada 3rd edition 2010 httpwwwnetldoegovtechnologiescarbonseqrefshelfatlas

[10] S Bachu D Bonijoly J Bradshaw et al ldquoCO2 storage capacityestimation methodology and gapsrdquo International Journal ofGreenhouse Gas Control vol 1 no 4 pp 430ndash443 2007

[11] S Bachu ldquoReview of CO2 storage efficiency in deep salineaquifersrdquo International Journal of Greenhouse Gas Control vol40 pp 188ndash202 2015

[12] A Goodman A Hakala G Bromhal et al ldquoUS DOEmethod-ology for the development of geologic storage potential forcarbon dioxide at the national and regional scalerdquo InternationalJournal of Greenhouse Gas Control vol 5 no 4 pp 952ndash9652011

[13] H Zhang D Wen Y Li J Zhang and J Lu ldquoConditions forCO2 Geological Sequestration in China and some suggestionsrdquoGeological Bulletin of China vol 24 no 12 pp 1107ndash1110 2005

[14] Y Liu X Li Z Fang andB Bai ldquoPreliminary estimation of CO2storage capacity in gas fields in ChinardquoRock and SoilMechanicsvol 27 no 12 pp 2277ndash2281 2006 (Chinese)

[15] X C Li Y F Liu B Bai and Z Fang ldquoRanking and screeningof CO2 saline aquifer storage zones in Chinardquo Chinese Journalof Rock Mechanics and Engineering vol 25 no 5 pp 963ndash9682006 (Chinese)

[16] J Guo D Wen S Zhang et al ldquoPotential and suitabilityevaluation of CO2 geological storage in major sedimentarybasins of Chinardquo Acta Geological Sinica (English Edition) vol89 no 4 pp 1319ndash1332 2015

[17] X Li N Wei Y Liu Z Fang R T Dahowski and C LDavidson ldquoCO2 point emission and geological storage capacityin Chinardquo in Proceedings of 9th International Conference onGreenhouse Gas Control Technologies GHGT-9 pp 2793ndash2800November 2008

[18] N Wei X Li Z Fang et al ldquoRegional resource distribution ofonshore carbon geological utilization in Chinardquo Journal of CO2Utilization vol 11 pp 20ndash30 2014

[19] R T Dahowski J J Dooley C L Davidson S Bachu andN Gupta ldquoBuilding the Cost Curves for CO2 Storage NorthAmericardquo Technical Report 20053 IEA Greenhouse Gas RampDProgramme 2005

[20] T Saaty The Analytic Hierarchy Process McGraw-Hill BookCompany New York NY USA 1980

[21] T Saaty and K KearnsAnalytical PlanningTheOrganization ofSystems vol 7 Pergamon Press Oxford Uk 1985

[22] RHaddadji ldquoThe In-SalahCCS experience Sonatrach Algeriardquoin Proceedings of the First International Conference on the CleanDevelopment Mechanism Riyadh Saudi Arabia September2006

[23] I Wright ldquoThe In Salah Gas CO2 Storage Projectrdquo in Pro-ceedings of The International Petroleum Technology Conferencepaper 11326 Dubai UAE December 2007

[24] O Skalmeraas ldquoThe Sleipner CCS experiencerdquo in Proceedings ofthe United Nations Framework Convention on Climate ChangeBonn Germany October 2014

[25] G Li and M Lu Atlas of Chinarsquos Petroliferous Basins [M]Petroleum Industry Press Beijing China 2nd edition 2002

[26] X Wu Carbon dioxide capture and geological storage-The FirstMassive Exploration in China Science Press 2013

[27] S Bachu and J J Adams ldquoSequestration of CO2 in geologicalmedia in response to climate change Capacity of deep salineaquifers to sequester CO2 in solutionrdquo Energy Conversion andManagement vol 44 no 20 pp 3151ndash3175 2003

Geofluids 17

[28] IPCC Special Report on Carbon Dioxide Capture and StorageCambridge University Press Cambridge UKNew York NYUSA 2005

[29] C M Oldenburg ldquoScreening and ranking framework forgeologic CO2 storage site selection on the basis of health safetyand environmental riskrdquo Environmental Geology vol 54 no 8pp 1687ndash1694 2008

[30] Y Diao S Zhang J Guo X Li J Fan and X Jia ldquoReservoirand caprock evaluation of CO2 geological storage site selectionin deep saline aquifersrdquo Rock and Soil Mechanics vol 33 no 8pp 2422ndash2428 2012

[31] S Liu M Zha J Qu and Z Chen ldquoCharacteristics and sealingability of mid-deep layer caprock in Dongying depressionrdquoJournal of Oil and Gas Technology vol 30 no 2 pp 390ndash3932008

[32] J Ye Q Wu and Z Wang ldquoControlled characteristics ofhydrogeological conditions on the coalbed methane migrationand accumulationrdquo Journal of China Coal Society vol 26 no 5pp 459ndash462 2001

[33] General Administration of Quality Supervision Inspection andQuarantine of China StandardizationAdministration of China2005 GB 17741-2005 Project site seismic safety evaluation

[34] K Pruess ldquoOn CO2 fluid flow and heat transfer behavior in thesubsurface following leakage from a geologic storage reservoirrdquoEnvironmental Geology vol 54 no 8 pp 1677ndash1686 2008

[35] J-M Lemieux ldquoReview the potential impact of undergroundgeological storage of carbon dioxide in deep saline aquifers onshallow groundwater resourcesrdquo Hydrogeology Journal vol 19no 4 pp 757ndash778 2011

[36] YDiao S Zhang YWang X Li andHCao ldquoShort-term safetyrisk assessment of CO2 geological storage projects in deep salineaquifers using the Shenhua CCS Demonstration Project as acase studyrdquo Environmental Earth Sciences vol 73 no 11 article65 pp 7571ndash7586 2014

[37] J Fan J Guo S Zhang and X Ji ldquoCO2 geological storagesuitability assessment of sichuan basinrdquo Journal of AppliedMathematics and Physics vol 02 no 11 pp 1009ndash1021 2014

[38] MLR (Ministry of Land and Resources of the Peoplersquos RepublicofChina)TheNationalOil andGas Resources Evaluation ChinaLand Press Beijing China 2010

[39] MLR (Ministry of Land and Resources of the Peoplersquos Republicof China)TheNational Coalbed Methane Resources EvaluationChina Land Press Beijing China 2009

[40] Z Zhao H Zhou X Chen et al ldquoSequence lithofacies paleo-geography and favorable exploration zones of the permian insichuan basin and adjacent areas Chinardquo Acta Petrolei Sinicavol 33 no 2 pp 35ndash51 2012

[41] J Du Natural Gas Exploration of PermianmdashTriassic Reef ampOolite in Sichuan Basin Petroleum Industry Press BeijingChina 2010

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal of

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal of

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in