seismic characterization of hypogenic karst systems...

Research ArticleSeismic Characterization of Hypogenic Karst SystemsAssociated with Deep Hydrothermal Fluids in the Middle-LowerOrdovician Yingshan Formation of the Shunnan AreaTarim Basin NW China

Hongtao Zhu Xiu Zhu and Honghan Chen

Key Laboratory of Tectonics and Petroleum Resources China University of Geosciences Ministry of Education Wuhan 430074 China

Correspondence should be addressed to Hongtao Zhu htzhucugeducn

Received 3 March 2017 Revised 11 May 2017 Accepted 27 July 2017 Published 13 September 2017

Academic Editor Zhijun Jin

Copyright copy 2017 Hongtao Zhu 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

Two fundamental forms of hypogenic karst systems (lateral stratiform hypogenic and cross-formational fault-vein hypogenic karstsystem) are distinguished mainly by differential effects of preexisting faults In seismic cross sections hypogenic karst systemsare expressed as complex string-beads-like seismic reflections associated with faults In this study a new seismic characterizationworkflow was developed including seismic amplitude thresholding fault interpretation pickup and merge display to enhancethe description of the spatial distribution and coupling of hypogenic karst system and faults The results suggest that the lateralstratiform hypogenic karst systems are predominantly developed at the top of the secondary faults presenting an overall of ldquolayereddistribution and finger-like interactionrdquo features The cross-formational fault-vein hypogenic karst systems are developed aroundfaults and characterized by dendritic distribution Furthermore we infer that the development pattern of hypogenic karst systemshas been produced by the interplay of the faults preexisting epigenic karst systems and lateral carrier-beds which together combinethe complex hydrothermal migration pathways of fluids with the characteristics of vertical and horizontal combined pathways Inaddition some possible controlling factors (eg sequence stratigraphic boundaries paleogeomorphology and sedimentary facies)that can influence the development of these hypogenic karst systems have been discussed in detail

1 Introduction

It has been well documented that there exists tremendousexploratory potential of the deep subsurface which hasrecently drawn attention of petroleum geologists worldwide(eg [1ndash3]) One of the formingmechanisms of deeply buriedcarbonate reservoirs (gt4500m) is related to dissolutioneffects by fluids in the deep subsurface (eg [4 5]) Thefluids here are not meteoric in origin but typically referto hydrothermal fluids which enter the relatively shallowsubsurface from deep along the faults Hypogenic karstsystems influenced by deep hydrothermal fluids contributeto the formation of the quality deep carbonate reservoirsand have been found in the Yingshan Formation (gt6000m)of the Shunnan area Tarim Basin NW China In addi-tion hydrothermal minerals (calcite quartz and tabularanhydrites) provide evidence that hypogenic karst systems

affected by hydrothermal fluids are also found in the Ying-shan Formation Clearly understanding the characteristics ofhypogenic karst systems developed in Yingshan Formation istherefore of significance to optimizing petroleum explorationand increasing reserves

Hypogenic karst is a genic type of karst regardless ofthe lithologies in which it develops [6 7] Speleogenesis isoften considered as the primary mechanism of the formationof karst because almost all essential attributes of karst owetheir origin to speleogenesis [7] Two fundamental typesof speleogenesis hypogene and epigene are differentiatedmainly by the distinct hydrodynamic characteristics of therespective groundwater flow systems (1) stratiform confinedaquifer systems or across-formational fracture-vein flowsystems of varying depths and degrees of confinement and(2) hydrodynamically open near-surface unconfined systems

HindawiGeofluidsVolume 2017 Article ID 8094125 13 pageshttpsdoiorg10115520178094125

2 Geofluids

(a)

Kuqa Depression

Maigaiti slope

Tabei

Kongquehe

Southwest Depression Southeast

DepressionCentral

SoutheastUpliftUplift

Tianshan Mountain

Kunlun Mountain

Tazhong Uplift

0 200(km)

(km)

0 1000

N

TarimN

SN5

SN7SN6

SN1SN4

Shuntuoguole

Low uplift

Shuntuoguole

gentle slope

GuchengxuLow uplift

Khattak Uplift

0 20

FaultStructural boundaryWell location

Shunnan area

N

Slope

(b)

Boundary fault 1

Mangar sag

++

+

+

+

+

(km)

Peoplersquos

of ChinaRepublic

Uplift

Study area

83∘ 52

39∘

00

38∘

30

85∘ 23

Figure 1 Location of the Shunnan area in the Central Tarim Basin NW China (a) Location of the Tarim Basin in China and the Tazhonguplift in Tarim Basin (b) Main tectonic units of the Shunnan area

[7] Accordingly the principal difference between hypogenicand epigenic karst systems lies in the modes (confinedversus unconfined) and principal vectors (ascending versusdescending) of fluid circulation and in the source of rechargeto a given unit (recharge from depth versus recharge from theoverlying or immediately adjacent surface) [6 7]

There have been many case studies on carbonate karstover the past six decades but they deal mainly with epigenickarst systems (eg [8ndash14]) The progress on the charac-terization of the hypogenic karst systems (eg [15ndash19])predominantly focuses on the planar- or section-view delin-eations of lateral stratiform hypogenic karst system zonesand relevant fault system zones individually The ldquolateralstratiform hypogenic karst system zonerdquo is used to denote thezone where fluids are directed transversely flow across layersand formation and in which fluids related to upwelling flowsfrom the deep subsurface and upwards migrate along thefaults The relevant ldquofault system zonerdquo in this paper not onlydenotes the migration pathways (faults) of ascending fluidsthat contribute to the formation of hypogenic karst systembut also refers to the ldquocross-formational fault-vein hypogenickarst systemrdquo which is characterized by developing parallelaround faults

The Shunnan area is a three-level structural unit withinthe Tarim Basin located at the downthrown side of theboundary fault I of the Tazhong Low uplift (Figure 1) Itis bounded to the west by the Khattak Uplift north bythe Shuntuoguole Low uplift south by the Guchengxu Lowuplift and east by the Mangar sag (Figure 1) In recent yearshydrothermal minerals (calcite and quartz in veins and tab-ular anhydrites) at depths (gt6000m) and distinctive seismic

reflections that are expressed by a series of individual string-beads lateral spreading have been found in the Shunnan areaThese provide the potential conditions to characterize thedistribution of the hypogenic karst systems

The aim of this paper is to understand the spatial distribu-tion and controlling factors of hypogenic karst developmentand develop a model of the karst systems in the Middle-Lower Ordovician Yingshan Formation of Shunnan areaTarim Basin NW China In this paper the hypogenic karstsystems and faults were first distinguished on the basis ofan integrated approach of seismic data with available con-ventional cores wells and a scanning electron microscopeanalysis and then a new seismic characterization workflowwas developed including seismic amplitude thresholdingfault interpretation pickup andmerge display to enhance thedescription of the spatial distribution and coupled hypogenickarst systems and faults The proposed workflow will providenew insight into 3D seismic characterization of the hypogenickarst systems and can be used extensively in hypogenic-related karst basins around the world

2 Geological Setting

The Tarim Basin in western China (Figure 1) is a compositebasinwith a number of uplifts and depressions that developedas a result of a long and complicated tectonic history (eg[20ndash26]) It is located between the Tianshan Mountain andKunlun mountains occupying an area of 56 times 104 km2The basinrsquos east-west length is 1400 km while the maximumwidth reached 520 kmwith the altitude ranges between 800mand 1300m Collectively the development of the basinrsquos

Geofluids 3

Series Formation Seismicreference Lithology

Mid

dle-

Low

erO

rdov

icia

n

Yingshan

Yijianfang

Penglaiba

MarlsMicrite limestone

Arenite limestone

Dolomite

４74

４75

４76

４78

４80

Figure 2 Generalized stratigraphic column of the Middle-LowerOrdovician of the Tarim Basin showing lithology and seismicreference The study interval is the Yingshan Formation

current configuration and the geometry of tectonic elementsare controlled mainly by multiple tectonic activities TheTarim Basin is mainly divided into three uplifts and fourdepressions From the north to the south there are theKuqaDepression Tabei Uplift NorthernDepression CentralUplift SouthwestDepression SoutheastUplift and SoutheastDepression (eg [27ndash29] Figure 1(a))

The Tazhong Low uplift is located in the middle part ofthe Central Uplift in the Tarim Basin covering an area of 29times 104 km2 and the terrain dips to northwest generally likea bird foot or a broom (eg [29] Figure 1(a)) The MiddleOrdovician in the Tazhong area is subdivided into Yingjian-fang and Yingshan Formations The Lower Ordovician issubdivided into Yingshan and Penglaiba Formations Afterthe deposition of Lower Ordovician Penglaiba FormationTazhong area subjected to compression started to uplift

The study area (Figure 1(b)) is a three-level structuralunit located at downthrown side of the boundary fault I ofTazhong Low uplift within Tarim Basin It adjoins KhattakUplift bounded by the boundary fault I on the western sideto the north it is adjacent to the Shuntuoguole Low upliftThe gentle slope connects Guchengxu Low uplift to the southandMangar sag to the east respectivelyThe lower part of theYingshan Formation was subjected to long-term exposureforming intensive epigenic karst systems To the contrary theupper part of the Yingshan Formation did not experienceexposure after deposition and a large amount of hypogenickarst systems was found in the upper part of the YingshanFormation Seismic references T8

0 and T74 are the base and

top of the Middle-Lower Ordovician T78 and T7

5 are thebase and top of the Middle-Lower Ordovician YingshanFormation and T7

6 is the interface between the upper andlower Yingshan Formation Those seismic references areshown in Figure 2

The hypogenic karst systems are defined as the formationof caves by water that recharges the soluble formation frombelow driven by hydrostatic pressure or other sources ofenergy and independent of the recharge from the overlyingor immediately adjacent surface (eg [15]) It has beenproved that carbonatesmay produce a series of geological andgeochemical changes in the hydrothermal process and thesechanges may be reflected by mineralogy and geochemistry[30] The hydrothermal fluids often contain some acid gasessuch as CO2 and H2S [31] dissolve the original carbonatesby the water-rock reaction and form the hydrothermallyassociated minerals such as the fluorite chlorite sphaleriteand barite and even the hydrothermal mineral association[32] Hydrothermal processes commonly form the associatedminerals such as calcite quartz and tabular anhydrite in wellSN4 (Figure 3) Present temperature is the highest temper-ature in the geological buried process of the Yingshan For-mation [33] and geothermal gradient of the Shunnan area is20sim23∘C100m [34 35] Therefore the highest temperaturein well SN4 of the Yingshan Formation is about 153sim173∘CThe homogenization temperature of the original inclusionrepresents the temperature of the hydrothermal fluid [30]The main homogenization temperatures of primary fluidinclusions in calcite and quartz are higher than the highesttemperature of about 25∘C in well SN4 [33] so the calcite andquartzmust have been formed in high-temperature conditionwhichmay bemainly caused by hydrothermal fluids from thedeep subsurface

3 Seismic Facies Variations between Epigenicand Hypogenic Karst Systems

Classic seismic facies are groups of the characteristics ofseismic reflections which differ from those of adjacent areas(eg [36]) Paleokarst seismic facies are extremely com-plex Previously published studies provide valuable insightsinto seismic evidence of paleokarst facies (eg [23 24 3738]) Key seismic parameters include reflection amplitudecontinuity of seismic events apparent frequency externalform and internal reflection configurationThe variations areutilized to infer the underlying geology (eg [23 24 39])In this paper two typical seismic facies referred to as theindividual string-beads-like and complex string-beads-likeare identified to describe the seismic reflections of epigenicand hypogenic karst systems respectively in the Middle-Lower Ordovician Yingshan Formation Detailed differencesbetween both string-beads-like individuals and complexesare expounded in the following

31 Seismic Facies of Epigenic Karst Systems As noted inKlimchouk [7] epigene karstification occurs in the near-surface conditions and is directly linked with recharge fromthe immediately overlying or adjacent surfaceThe individualstring-beads-like seismic reflection has been interpreted asthe evidences of ldquoepigenic karst systemrdquo in the Tarim Basin inthe published papers which is always linked with the termsldquounconformities weathering crusts exposure etcrdquo (Guoet al 2012 Chen et al 2014) [40 41] These terms are furtherrelated to the epigenic karst system development Guo et al

4 Geofluids

Marls

Arenite limestone

Micrite limestone

6670 6671 6672 66736669

(g)(e)(d)(f)(c)(b)

(a)

Quartz

Centimeter-scalehoneycomb

residual pore1 cm

(b)

Quartz

Half-fillingresidual pore

1 cm

(c)

Dolomite

Millimeter-scalehoneycomb

residual poreAutomorphic

quartz

Half-fillingresidual fracture

1 cm

(d)

Calcite Iceland spar

1 cm

(e)

Keatite

Residual pore

(f)

Slab plaster

(g)

Figure 3 Petrologic characteristics of the Yingshan Formation determined fromwell SN4 (a) Lithology of well SN4 from 66683 to 66735m(b) Centimeter-scale honeycomb residual pores 666947m (c) Half-filling residual pores along the fractures 667044m (d) Half-fillingresidual pores along the fracture and millimeter-scale honeycomb residual pores 667057m (f) Quartz in vein 667048m (e) Iceland spar(calcite) 667225m (g) Tabular anhydrite 667298m

(2012) pointed out the individual string-beads-like seismicreflection in Yingshan Formation is attributed to weatheringkarst (epigenic karst) Chen et al (2014) demonstrated theindividual string-beads-like seismic reflection (strong orweakamplitude) is attributed to ldquoepigenic karst systemrdquo on thebasis of analysis of conventional cores wells and loggingsin Yingshan Formation Tarim Basin In this paper theauthor thought the development of karst system in YingshanFormation is linked with the exposure environment andrelated to meteoric fluids Gao et al [40] demonstratedthat the individual string-beads-like seismic reflection in the

Tazhong area is linked with the exposure environment Inthis paper the moldic and dissolution pores in well Shun2(at depth of 68795m) are formed in the meteoric freshwater environment as a result of the repeated exposure of thecarbonate platform In addition fibrous calcite cementationin well Shun6 (at the depth of 66469m) is also the indicatorof the meteoric fresh water environment

In the study area many high-amplitude low-continuousindividual string-beads-like seismic reflections were recog-nized in the lower part of the Yingshan Formation in theseismic cross sections (Figures 4(a) and 4(b)) These seismic

Geofluids 5

+

+

A

Well location

FaultHypogenic karst

Complex string-bead-likeseismic reflection

SE(e)

SE(f)SN4(d)

0 2(km)

0 2(km)

0 2(km)

E

Seismic profileEpigenic karst

SN5SN6

0 4(km)Tw

o-w

ay tr

avel

tim

e (s)

Two-

way

trav

el ti

me (

s)

(b)

Individual string-beads-likeseismic reflection

SE(a)

(c)

A

A

＄

BC

D

＄

B C D

+

+

+

+

+

+

+

+

+

50

40

50

35

４75

４76

４78

４80

４81

４74

４76

４78

４80

N

N

SN1

SN4SN6 SN7

SN5

0 8(km)

SN1

SN6 SN7

SN5

Figure 4 Seismic facies of epigenic karst systems and hypogenic karst systems of the Yingshan Formation in the study area (a) Seismicattribute RMS (root mean square) map of the lower part of the Yingshan Formation (b) Epigenic karst systems marked by the blue oval lineacross wells SN6 and SN5 seismic section showing the typical individual string-beads-like seismic reflections (c) Seismic attribute RMS (rootmean square) map of the upper part of the Yingshan Formation (d) Complex string-beads-like seismic reflections of hypogenic karst systemsacross well SN4 seismic section developed associated with the faults (e) and (f) Other seismic section showing complex string-beads-likeseismic reflections of hypogenic karst systems developed associatedwith the faultsThe blue color indicates epigenic karst systems distributedwidely in the entire study area with the isolated punctate distributions the green color indicates hypogenic karst systems showing belt-shapeddistributions along the SN4 fault zone

reflections are characterized by multiple strong amplitudeswith vertical build-ups and worm-like short-axis appear-ances forming near-vertical columns referred to as string-beads [41] They predominantly reflect the distribution ofthe epigenic karst systems Apart from the individual string-beads-like seismic reflections the strata are characterizedby continuous parallel or subparallel seismic reflections(Figure 4(a) see [42])

The seismic amplitude attribute (root mean square-RMS)map indicates that the isolated punctate anomalies caused bythe individual string-beads-like seismic reflections of epigenickarst systems are widely distributed across the entire studyarea This reveals that the epigenic karst systems are welldeveloped in the lower part of the Yingshan Formation of thestudy area (Figure 4(a))

32 Seismic Facies of Hypogenic Karst Systems A set ofhypogenic karst systems (lateral stratiform hypogenic andcross-formational fault-vein hypogenic karst systems) wasrecognized in the Upper Yingshan Formation of well SN4area and the cross-well seismic sections Differing withparallel or subparallel seismic reflections of the strata andindividual string-beads-like seismic reflections of the epigenic

karst systems seismic reflections of hypogenic karst systemsare usually composed of a series of individual string-beadsdefined as a string-beads complex (Figures 4(c) 4(d) 4(e)and 4(f)) Furthermore compared with the isolated distribu-tion of epigenic karst system in planar view the string-beadscomplex of hypogenic karst systems is belt-shaped distributedalong the faults in the planar view and the section view (1)lateral stratiform hypogenic karst systems are well developedat the top of the secondary faults and cross-formational fault-vein hypogenic karst systems are developed around the faultsthrough the seismic cross sections (Figures 4(d) 4(e) and4(f)) (2) lateral stratiform hypogenic and cross-formationalfault-vein hypogenic karst systems are well developed alongthe SN4 fault zone in the seismic attribute RMSmap showingthe characteristics of a belt-shaped distribution and string-beads complexes with distinctive strong amplitude anomalies(Figure 4(c))

4 3D Seismic Characterization of HypogenicKarst Systems

Investigations of hypogenic karst systems predominantlyfocus on the section- or planar-view delineation of a lateral

6 Geofluids

Mergedisplay

Faultinterpretation

Seismicamplitudethresholdingdisplay

Pickup

Pickup(a)

(b)

(c)

N

N

lateral

obli-que

Top

Seismic data

Z

X

Y

Z

XY

Z

XY

ZX

Y

Z

X

Y

25 km

2 km

1 km

Figure 5 A new 3D seismic characterization workflow for hypogenic karst systems including seismic amplitude thresholding faultinterpretation pickup and merge displays 3D view of hypogenic karst systems in the study area ((a) (b) and (c)) (a) Coupling relationshipsbetween faults (multilevel faults) and hypogenic karst systems (b) and (c) showing the lateral oblique and top distributions of hypogenickarst systems respectively Red and blue color represent hypogenic karst systems

stratiform hypogenic karst system and the relevant faultsystem zone individually (eg [38 43ndash47])

Recently acquired 3D seismic data covering the entirestudy area make it possible to investigate the seismic faciesand distributions of hypogenic karst systems [23 24] A newseismic characterization workflow has been developed inthis study including seismic amplitude thresholding faultinterpretation pickup and merge display to conduct a jointinvestigation of the spatial distribution and coupling of thelateral stratiform hypogenic karst system and relevant faultsystem zones (Figure 5) The relevant fault system zones areused in this paper to denote themigration pathways (relevantfaults) of hydrothermal fluids and the cross-formational fault-vein hypogenic karst systems around faults

The workflow includes the following steps (Figure 5)

(1) Carry out the logging and seismic facies analysisbased on 3D seismic data and drilling data taking intoaccount detailed comparisons of well-to-seismic tiesand then conclude with the characteristics of lateralstratiform hypogenic karst systems and their relevantfault system zone by analyzing seismic facies acrossdifferent seismic lines

(2) Characterize the hypogenic karst systems (lateralstratiform hypogenic and cross-formational fault-vein hypogenic karst systems) on the basis of theattributes of strong seismic amplitude and high con-tinuity

(a) Firstly picking the overall attributes of the rootmean square to determine the seismic ampli-tude classification standards and then definingthe seismic amplitude distribution ranges of thehypogenic karst system especially the minimalseismic amplitude value is required

(b) Secondly display the part of the amplitude thatis higher than the minimum amplitude valuethrough seismic amplitude thresholding andstrong amplitude pickup

(c) Finally characterize the spatial distribution ofhypogenic karst system according to the aboveresults

(3) Display the spatial distribution of relevant faultsthrough fault interpretation pickup and thresholdingdisplay

(4) Merge displays lateral stratiform hypogenic karstsystems and fault system zones

5 Characterization Results ofHypogenic Karst Systems

Applying the proposed new seismic characterization work-flow a series of the spatial configuration diagrams showhypogenic karst systems and relevant faults further analyzingtheir coupling relationship from different perspectives (Fig-ures 5(a) 5(b) and 5(c))

Geofluids 7

Hypogenic karst systems constituted lateral stratiformhypogenic karst system and cross-formational fault-veinhypogenic karst system [7 48] Deep fluids upwards flowedalong the faults and at the same time transversely migratedalong the soluble formation and lateral stratiform hypogenickarst system is thus formed Lateral stratiform hypogenickarst systems are predominantly characterized by an overallview of ldquohorizontal layered distribution with certain lateralcontinuityrdquo (Figure 5(a)) With the accumulation of fluidslateral stratiform hypogenic karst systems are integratedand cut-through making the layered characteristic apparent(Figures 5(a) 5(b) and 5(c)) It is shown in Figure 5(c) thatlateral stratiform hypogenic karst systems formed in differentlocations at the top of the same faults generally exhibit theobvious amplitude abnormities Seismic amplitudes decreasegradually away from faults or top downwards of faults reveal-ing the karstified range and intension decreasing graduallydownwards in the lateral stratiform hypogenic system zonesCross-formational fault-vein hypogenic karst system is usu-ally formed around the faults that is the fault systems zoneis cross-formational fault-vein hypogenic karst developmentzone

The importance of faults in hypogenic karst systemis reflected in two aspects On the one hand faults arevertical migration pathways of hydrothermal fluids whichare important for upwelling cross-communication betweenshallow and deep subsurface and further for lateral stratiformhypogenic karst system development Because fluids in faultsystems encounter the lateral carrier-beds (the unconformi-ties weathering crusts and preexisting epigenic karst sys-tems) fluids occur in lateral selective dissolution due to thehigh permeability of lateral carrier-beds and the lateral strati-formhypogenic karst systems are developed (Figure 5(a)) Onthe other hand fault zones are also cross-formational fault-vein hypogenic karst development zones where ascendingflows cross soluble and insoluble rocks Accordingly cross-formational fault-vein hypogenic karst systems are developedaround faults by the dissolution effects of fluids on massiverocks [6 7] In addition the faults comprised the primaryfaults and secondary faults with different characteristicsPrimary faults are much rougher and their cross sectionsoften exhibit the circular or elliptic physical characteristicsConversely the secondary faults are developed in threedirections vertical horizontal and bending and divergencein multiple directions and their shape sizes have distinctdifferences small to large (Figure 5(b))

6 Development Pattern of HypogenicKarst Systems

Based on the detailed characterization of hypogenic karst sys-tems in the study area the development pattern of hypogenickarst systems is proposed where deep hydrothermal fluidsmigrated vertically through primary and secondary faultsand flowed laterally through lateral carrier-beds (includingunconformities weathering crusts the preexisting epigenickarst system porous or vuggy layers) The pattern showsthat the hypogenic karst system has overall ldquovertical and

horizontal combination dendritic distribution layered dis-tribution and finger-like interactionrdquo features (Figure 6)

The vertical faults formed by primary and secondaryfaults have a positive effect on the development of hypogenickarst systems The deep hydrothermal fluids flowed upwardsalong the multilevel faults presenting ldquodendritic distribu-tionrdquo features Subsequently fluids migrated along the lateralcarrier-beds horizontally presenting ldquolayered distributionrdquocharacteristics The strata were subjected to selective dissolu-tion in the course of the lateral migration presenting typicalldquofinger-like interactionrdquo characteristics Faults and lateralcarrier-beds together formed a ldquovertical and horizontal com-binationrdquo of hydrothermal migration pathways Hypogenickarst systems have an overall ldquodendritic distribution layereddistribution and finger-like interactionrdquo features (Figure 6)

ldquoDendritic distributionrdquo means that the hypogenic karstsystem is characterized by a multiple-level ldquodendriticrdquo mor-phology Primary faults are the ldquotrunksrdquo of vertical channelsand secondary faults are ldquobranchesrdquo accompanied by thediffusion of the hydrothermal fluids In addition the dis-solved pores karst cave and dolomite reservoirs are furtherbranches developed at the top of the secondary faults (Fig-ure 6)

Hydrothermal fluids migrated upwards along the sec-ondary faults forming an intensive dissolution area Thenhydrothermal fluids migrate horizontally along the lateralcarriers forming the ldquolayered distributionrdquo of dissolved poressystems In addition the dissolved pore systems formedby different secondary faults were fused and penetratedmaking the ldquolayered distributionrdquo apparent At the same timewhen the hydrothermal fluids converged on the top of thesecondary faults selective dissolution gave priority to solublesparry calcarenite compared with micrite Altered solublesparry calcarenite and unaltered micrite presented the char-acteristics of interbedding and alternative occurrence Morespecifically the strata consisted of altered sparry calcareniteaccompanied by unaltered micrite interbed

In summary hypogenic karst systems can be interpretedas a tree-like cave system with an erect trunk in the bottombending in multiple directions upwards and changing intohorizontal at the top showing overall ldquovertical and horizontalcombination dendritic distribution layered distribution andfinger-like interactionrdquo features (Figure 6)

7 Controlling Factors for HypogenicKarst Systems

The main controlling factors of the Ordovician karst sys-tems are uplift unconformity fault systems rock physicalproperties and sedimentary facies [13 26] In order toillustrate the spatial distributions this paper will present thecontrolling factors of the hypogenic karst system through theanalysis of fault systems sequence stratigraphic boundariespreexisting epigenic karst systems paleogeomorphology andsedimentary facies

71 Relationships between Fault Systems and Hypogenic KarstSystems Based on the distinct seismic reflections between

8 Geofluids

SN4

Two-

way

trav

el ti

me (

s)

0 2(km)

E

50

40

++

++

+

SN1 SN5

SN6 SN7SN4

４74

４75

４76

４78

４80

(a)

Arenite limestone

Well location

Mud stone

Fluids

SN4

SN4Original system

Hypogenic karst system

2yj

1p

3

2

1

Lateral alteration

Karst cave

Dolomitic limestone

Limestone

Fault

Lime dolomite Gypsum dolomite

Dolomite

Vertical alteration

Stratum

y11-2

y1-2

y21-2

(b)

Figure 6 Development pattern of hypogenic karst systems of the study area (a) Seismic dip section DD1015840 showing complex string-beads-like seismic reflections of hypogenic karst systems in the Yingshan Formation (b) Hydrothermal fluids pathways derived fromthe deep subsurface showing vertical pathways (primary-secondary faults) and lateral carrier-beds (preexisting epigenic karst systemsunconformities soluble layers etc) Accumulations of hydrothermal fluids make it possible for the scattered lateral carrier-beds tocommunicate with one another and formed hypogenic karst systems with such features as dendritic distribution layered distribution andfinger-like interaction

Geofluids 9

the karst systems (low continuity and strong seismic ampli-tude) and surrounding rocks (high continuity and weakseismic amplitude) the planar distributions of epigenic andhypogenic karst systems in the Yingshan Formation wereshown in Figures 4(a) and 4(c) by using the seismic amplitudeattribute (RMS root mean square)

The seismic attribute RMS map shows that isolatedpunctate anomalies are widely distributed across the entirestudy area as recognition indicators of epigenic karst systemsin the lower part of the Yingshan Formation Converselya large amount of hypogenic karst systems are developedalong the SN4 fault zone in the upper part of the YingshanFormation located at the top of the secondary faults (Figures4(d) 4(e) and 4(f)) Therefore preexisting epigenic karstsystems and faults influenced the distributions of hypogenickarst systems which were also utilized to interpret the reasonwhy hypogenic karst systems focused distributing along thefaults in the upper part of the Yingshan Formation It isexplained further below

711 Faults There are four periods of tectonic activities in theShunnan area of the Tarim Basin the Early andMiddle Cale-donian phases the Late Caledonian to the Early Hercynianphases and the Late Hercynian phases The tectonic stressintensity developed moderately during the Early Caledonianphases and then subsequently increased during the Middle-Late Caledonian to the Early Hercynian phases after whichthe strength gradually weakened during the Late Hercynianstage

The structural fractures of compressional torsional strike-slip faults are wider and easily developed in comparisonto transtensional strike-slip faults which depend on theproperties of strike-slip faults and petrophysical character-istics of carbonate rocks [49] Two major strike-slip faultsystems trending NE and NNE are present in the Shunnanarea under control of the compressional torsional strike-slipfault tectonic activity of Episode I of the mid-CaledonianBecause the intensity of the NNE strike-slip fault activity iscomparatively weak the fracture scale is smaller and it doesnot have hereditability in the late period Conversely theNE strike-slip fault cuts through multiple layers and reachesthe Sinian system Hydrothermal fluids below the basementmigrate upwards along the strike-slip fault and react with theOrdovician carbonate strata [30 33]

The SN4 fault system is a typical instance of the northeast-southwest-trending strike-slip faults systems and the struc-ture style of which was strongly influenced by the transten-sional tectonic stress from the Late Caledonian to earlyHercynianThe positive flower structure occurred as tectonicinversion finally forming a series of tensile normal faultsThetensile normal faults are good vertical migration pathwayswhich provide favorable conditions for the hydrothermalfluids tomigrate upward In addition the vertical conductionthrough faults is superior to the lateral conduction throughthe effective carbonate reservoir so fluidswill choose effectiveand opened faults while migrating upward thus hypogenickarst systems are developed around and at the end of openedfaults (Figures 4(d) 4(e) and 4(f)) showing a belt-shapeddistribution along the SN4 fault belt (Figure 4(c))

712 Epigenic Karst Systems Epigenic karst systems aredeveloped in the lower part of the Yingshan Formationbecause the Shunnan area was subjected to intensive disso-lution as a result of long-term exposure as sea level descendsthough with no strong tectonic uplift activities this time Onthe contrary epigenic karst systems are comparatively lessdeveloped in the upper part of the Yingshan Formation with-out exposure condition because the area was under controlof the tectonic activity of Episode I in mid-Caledonian andlocated at downthrown side of fault resulting in no exposureat surface after the deposition of Yingshan and YijianfangFormations

However recent interpretations considered the impor-tance of preexisting epigenic karst systems as effectivepermeability formations [33] They provide conductive con-ditions for the lateral dissolution and are beneficial forthe formation of lateral stratiform hypogenic karst systemsHydrothermal fluids from the deep migrate to the top ofsecondary faults and then along preferential permeabilityformation to migrate laterally making it possible for string-beads-like individuals of the scattered epigenic karst systemsto communicate with each other and become string-beads-likes complexes of a massive hypogenic karst systems

72 Relationships between Sequence Boundaries and Preex-isting Epigenic Karst Systems Based on the principles ofsequence stratigraphy and taking into account the empiricallyderived base level volumetric partitioning and facies varia-tions we proposed sequence stratigraphic framework for theYingshan Formation It includes two third-order sequencesnamely SQ2 and SQ3 from bottom to top (Figure 7)Sequences SQ2 and SQ3 correspond to the lower and upperparts of the Yingshan Formation respectively

Karst systems of the Yingshan Formation were metic-ulously identified calibrated and correlated by well logdata combined with previous studies [40 50] The resultsspeculated that two different types of the karst system arepresent in the sequences SQ2 and SQ3 respectively

Sequence SQ2 is predominantly characterized by indi-vidual string-beads-like seismic reflection (Figure 7) Thedistributions of epigenic karst systems and sequence bound-aries are related showing the developments of epigenic karstsystems correspondingly migrated to top from bottom of thesequence boundary from highlands to lowlands (Figure 7)The reason is that highlands experienced long-term intensiveerosion and surface denudation than that of lowlands as thesea level falls geomorphically causing wide ranges of epigenickarst systems developed close to the bottom of the sequenceboundary

Sequence SQ3 is predominantly characterized by com-plex string-beads-like seismic reflections (Figures 4(c) 4(d)4(e) and 4(f)) The carbonate platforms began to enter theburial stage after experiencing multiple tectonic subsidenceFaults caused by the tectonic activities provide the potentialpathways for the hydrothermal fluids to migrate upwardsThus deep hydrothermal fluids entered the overlying car-bonate strata near the fault and dissolved soluble layersproducing the formation of hypogenic karst systems

10 Geofluids

Topographic highland

Topographic lowland

Top BaseSQ2

SQ3

0 8(km)

SN7SN4SN5SN1

SN6Two-

way

trav

el ti

me (

s)

+

+

+

+ +

50

45

35

T74

T76

T75

T80

T78

Figure 7 Seismic dip section showing individual string-beads-like seismic reflections of epigenic karst systems in the lower part of theYingshan Formation which developed near the base and top of sequence boundary in the topographic highland and lowland respectively

73 Relationships between Geomorphology and HypogenicKarst System Paleogeomorphology is a comprehensiveresponse of what a study area has experienced includingstructural deformation depositional infilling differentialcompaction weathering and erosion (eg [37]) Previousstudies and exploration efforts have confirmed that paleogeo-morphology is one of the key controlling factors for thedevelopment of epigenic karst (eg [51]) also applicable inShunnan area

The Shunnan area is dominated by platform faciesdeposits during Middle-Lower Ordovician which weredenuded to different degrees in different zones under controlof multiphased Caledonian-Hercynian tectonic uplift Tobetter understand the relationship between seismic geomor-phology and the distribution of hypogenic karst systems inthis area the paper is based primarily on interpretations of anintegrated data set including 3D seismic data and well dataThe paleogeomorphology in the upper part of the YingshanFormationwas reconstructed including topographic featuresof low uplifts gentle slopes and sags of the intraplatform(Figure 8) The paleogeomorphology framework is markedby widely distributed sags northwest and comparativelydeveloped low uplifts southeast whereas gentle slopes areoverall less developed (Figure 8)

In addition the paleogeomorphological map shows thathypogenic karst systems in the upper part of the YingshanFormation are widely distributed along the faults whichare located in the low uplifts of the intraplatform Thereason why hypogenic karst systems are easily distributedin the highlands is that geomorphically highlands of theintraplatform are easier places to develop a lot of dissolvedpores with good connectivity which are characterized bythe well development of vadose zones Furthermore thedissolved pores with good connectivity not only providemuch reservoir space for the original dense carbonate butalso superimpose faults to provide upward pathways for thefluids migration These factors contribute to the epigenickarst systems development and preexisting epigenic karstsystems in the lower part of the Yingshan Formation were aprecursor for subsequent hypogene karstification

Low

High

Hypogenickarst system

N

Low uplift

Low sag

Gentle slope

SN4

SN7

SN5

SN1SN6

Figure 8 Relationships of paleogeomorphology and hypogenickarst systems of the upper part of the Yingshan Formation showingbelt-shaped distributions at the highlands of themargin of intraplat-form along the SN4 fault zone

74 Relationships between Sedimentary Facies and HypogenicKarst Systems TheMiddle-Lower Ordovician Penglaiba andYingshan Formations are mainly a set of marine carbonateplatform facies deposits and they are also a typical restricted-open sedimentary sequence platform of transgression typeA dolomitic to limestone lithological trend exists from thePenglaiba to Yingshan Formation primarily showing thevariations from pure dolomite gray dolomite and dolomiticlimestone in the Penglaiba Formation to the granular andmicrite limestone in the Yingshan Formation (eg [52ndash54])

During the deposition of the Penglaiba Formation therestricted platform facies are primarily composed of micro-crystalline argillaceous dolomite and dolomudstone It cor-responds to a deposit formed in a restricted (partially closed)environment probably associated with poor water circula-tion caused by the sea-floor topography barrier In contrast

Geofluids 11

30

(km)

Karst plain facies

Slope

SlumpUnderfilled basin

Slump

Slump

SN7SN6

SN1 SN5SN4

N

FaultKarst plain faciesSlope

Underfilled basinWell

Sedimentary facies boundaryEpigenic karstHypogenic karst

+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘

Figure 9 Relationships of the sedimentary facies and hypogenic karst systems of the upper and lower part of the Yingshan Formationshowing well coupling between the distribution of intraplatform shoals and the development of hypogenic karst systems

with the ascent of sea level a small amount of limestoneoccurs as thin layer and intercalated in the dolomite duringthe deposition of the Yingshan Formation indicating smoothwater circulation

More previous studies revealed that a large number ofintraplatform shoals deposited in the Yingshan Formation[55ndash57] Sparry calcarenite is the main lithology of theintraplatform shola facies in the Tazhong area [58]The lithol-ogy gradually varies from the sparry calcarenite to micriteaway from the intraplatform shola facies Compared withthe micrite original porosities of sparry calcarenite are easilydeveloped andmore easily dissolved by the meteoric or high-temperature fluids and thus karst systems (epigenic karstand hypogenic karst) are easily developed in the area of theintraplatform sholas In the study area Figure 9 also showsthe close relationships between the intraplatform shoals andthe karst systems (epigenic and hypogenic karst systems)Intraplatform shoals are generally developed in geomorphi-cally highlands of the local super-shallow water

8 Conclusions

This study documented the presence of hypogenic karstsystems (lateral stratiform hypogenic and cross-formationalfault-vein hypogenic karst system) characterized by complexstring-beads-like seismic reflections in a data set from the

Tarim Basin The features are clustered near known faults inthe data set and this coupled with a new workflow usingseismic amplitude thresholding fault interpretation pickupand merge display to characterize the coupling relationshipbetween them leads us to propose the development patternof hypogenic karst systems Fluids expelled from the deepsubsurface move upwards along the vertical pathways (mul-tilevel faults) creating an aggressive fluid that is transportedto horizontally lateral carrier-beds further forming selectivedissolution The accumulations of fluids at the top of the sec-ondary faults make it possible for the formation of a massivehypogenic karst system of string-beads complexes with suchfeatures as dendritic distribution layered distribution andinterfingered bead strings

Potential controlling factors that influenced the develop-ment of hypogenic karst systems have been illustrated by avariety of end-member attributes that are distinct in termsof faults sequence boundaries preexisting epigenic karstsystems paleogeomorphology and sedimentary facies Thehypogenic karst systems are not evenly distributed across thestudy area but are most common in the highlands along thefaults where epigenic karst systems are usually developedbecause the residual space of an epigenic karst systemis conducive to the convergence of hydrothermal fluidsTrapped hydrothermal fluids from the deep scattered epi-genic karst systems communicate with one another and form

12 Geofluids

massive hypogenic karst systems In addition karst systemsdevelop in association with both the sequence boundariesand sedimentary facies The development of epigenic karstsystems migrates to the top from the bottom of the sequenceboundary from the highlands to lowlands It also has a closerelationship with the presence of intraplatform shoals

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research is sponsored by the National 973 researchprogram on ldquoTectonic evolution and the differences of hydro-carbon accumulation process of the Upper Paleozoic in theTarim Basinrdquo (no 2012CB214804)

References

[1] S Bloch R H Lander and L Bonnell ldquoAnomalously highporosity and permeability in deeply buried sandstone reser-voirs origin and predictabilityrdquo AAPG Bulletin vol 86 no 2pp 301ndash328 2002

[2] J M Ajdukiewicz P H Nicholson andW L Esch ldquoPredictionof deep reservoir quality using early diagenetic process modelsin the jurassic norphlet formation gulf of Mexicordquo AAPGBulletin vol 94 no 8 pp 1189ndash1227 2010

[3] X Pu L ZhouWWang et al ldquoMedium-deep clastic reservoirsin the slope area of Qikou sag Huanghua depression Bohai BayBasinrdquo Petroleum Exploration and Development vol 40 no 1pp 38ndash51 2013

[4] S J Mazzullo and P M Harris ldquoMesogenetic dissolution itsrole in porosity development in carbonate reservoirsrdquo AAPGBulletin vol 76 no 5 pp 607ndash620 1992

[5] A N Palmer ldquoGeochemical models for the origin of macro-scopic solution porosity in carbonate rocksrdquo in Unconformitiesand Porosity in Carbonate Strata A D Budd A H Saller andP M Harris Eds vol 63 of AAPG Memoir pp 77ndash101 1995

[6] A Klimchouk ldquoSpeleogenesis hypogenicrdquo in Encyclopedia ofCaves D C Culver andW BWhite Eds pp 748ndash765 ElsevierAcademic Press Chennai India 2nd edition 2012

[7] A Klimchouk ldquoThe karst paradigm changes trends andperspectivesrdquo Acta Carsologica vol 44 no 3 pp 289ndash313 2015

[8] D C Ford and P W Williams Karst Geomorphology andHydrology Unwin Hyman London UK 1989

[9] D Ford and P Williams Karst Hydrogeology and Geomorphol-ogy Wiley Chichester UK 2007

[10] A N Palmer ldquoOrigin and morphology of limestone cavesrdquoGeological Society of America Bulletin vol 103 no 1 pp 1ndash211991

[11] A N Palmer ldquoDistinction between epigenic and hypogenicmaze cavesrdquo Geomorphology vol 134 no 1-2 pp 9ndash22 2011

[12] H Hu Z Y Wang and Y F Zhang ldquoThe characteristics of theinterbeddingweathering crust karst in the Yingshan FormationNorth slope of the Tazhong UpliftrdquoXinjiang PetroleumGeologyvol 34 no 1 pp 277ndash281 2013

[13] F Renwei O Cheng P Yanjun et al ldquoEvolution modes ofinterbedded weathering crust karst a case study of the 1119904119905

and 2119899119889 members of Ordovician Yingshan Formation in EPCCblock Tazhong TarimBasinrdquoPetroleumExploration andDevel-opment vol 41 no 1 pp 49ndash59 2014

[14] Z M Wang L J Zhang and C H Sun ldquoClassification periodand exploration for carbonate karst in the Ordovician TarimBasinrdquo Journal of Palaeogeography vol 17 pp 635ndash644 2015

[15] A B Klimchouk Hypogene Speleogenesis Hydrogeological andMorphogenetic Perspective vol 36 of Special Paper No 1National Cave and Karst Research Institute Carlsbad NewMexico 2007

[16] K W Stafford L Land and A Klimchouk ldquoHypogenic speleo-genesis within seven rivers evaporites coffee cave eddy countyNew Mexicordquo Journal of Cave and Karst Studies vol 70 no 1pp 47ndash61 2008

[17] K Stafford L Land and G Veni Advances in Hypogene KarstStudies National Cave and Karst Research Institute CarlsbadCalif USA 2009

[18] A B Klimchouk and D C Ford Hypogene Speleogenesis andKarst Hydrogeology of Artesian Basins Ukrainian Institute ofSpeleology and Karstology Simferopol Crimean 2009

[19] T Chavez and P Reehling ldquoProceedings of Deep Karst OriginsResources andManagement of Hypogene Karst National Caveand Karst Research Institute Carlsbadrdquo 2016

[20] Z Q Gao T L Fan Z F Jiao and Y Li ldquoThe structuraltypes and depositional characteristics of carbonate platform inthe cambrian-ordovician of tarim basinrdquo Acta SedimentologicaSinica vol 24 no 1 pp 19ndash27 2006

[21] T L Fan B S Yu and Z Q Gao ldquoCharacteristics of carbonatesequence stratigraphy and its control on oil-gas in Tarim BasinrdquoGeoscience vol 21 pp 57ndash65 2007

[22] A J ShenW Q Pan X P Zheng L J Zhang Z F Qiao and NYMo ldquoTypes and characteristics of Lower Paleozoic karst reser-voirs in Tarim Basinrdquo Marine Origin Petroleum Geology vol15 pp 20ndash29 2010

[23] H Zeng R Loucks X Janson et al ldquoThree-dimensional seis-mic geomorphology and analysis of the Ordovician paleokarstdrainage system in the central Tabei Uplift northern TarimBasin western Chinardquo AAPG Bulletin vol 95 no 12 pp 2061ndash2083 2011

[24] H Zeng G Wang X Janson et al ldquoCharacterizing seismicbright spots in deeply buried Ordovician Paleokarst strataCentral Tabei uplift Tarim Basin Western Chinardquo Geophysicsvol 76 no 4 pp B127ndashB137 2011

[25] L Yun and Z Cao ldquoHydrocarbon enrichment pattern andexploration potential of the Ordovician in Shunnan area TarimBasinrdquo Oil and Gas Geology vol 35 no 6 pp 788ndash797 2014

[26] G Zhiqian L Zhongbao G Shanlin D Qunan W shiqiangand L Shilin ldquoCharacteristics and genetic models of LowerOrdovician carbonate reservoirs in southwest Tarim Basin NWChinardquo Journal of Petroleum Science and Engineering vol 144pp 99ndash112 2016

[27] C Z Jia Structural Characteristics and Oil amp Gas in the TarimBasin Petroleum Industry Press Beijing China 1997

[28] D F He X Y Zhou C J Zhang W J Yang and X Shi ldquoChar-acteristics of geologic framework of multicycle superimposedbasin in Tarim basinrdquo China Petroleum Exploration vol 11 no1 pp 31ndash41 2006 (Portuguese)

[29] X Lan X Lu Y Zhu and H Yu ldquoThe geometry and originof strike-slip faults cutting the Tazhong low rise megaanticline(central uplift Tarim Basin China) and their control onhydrocarbon distribution in carbonate reservoirsrdquo Journal ofNatural Gas Science and Engineering vol 22 pp 633ndash645 2015

Geofluids 13

[30] M Wu Y Wang M Zheng W Zhang and C Liu ldquoThehydrothermal karstification and its effect on Ordovician car-bonate reservoir in Tazhong uplift of Tarim Basin NorthwestChinardquo Science in China Series D Earth Sciences vol 50 no 2pp 103ndash113 2007

[31] J W Hedenquist and R W Henley ldquoThe importance ofCO2 on freezing point measurements of fluid evidence from

active geothermal systems and implications for epithermal oredepositionrdquo Economic Geology vol 80 no 5 pp 1379ndash14061985

[32] M Jebrak ldquoHydrothermal breccias in vein-type ore deposits areview of mechanisms morphology and size distributionrdquo OreGeology Reviews vol 12 no 3 pp 111ndash134 1997

[33] P J Li H H Chen D Q Tang et al ldquoCoupling relationshipbetween ne strike-slip faults and hypogenic karstification inmiddle-lower ordovician of ShunnanArea TarimBasin North-west Chinardquo Earth Science vol 42 no 1 pp 93ndash104 2017

[34] H L Li N S Qiu Z J Jin and Z L He ldquoGeothermal historyof Tarim basinrdquo Oil and Gas Geology vol 26 no 5 pp 613ndash6172005

[35] D Y Zhu Q Q Meng W X Hu and Z J Jin ldquoDifferencesbetween fluid activities in the Central and North Tarim BasinrdquoGeochimica vol 42 no 1 pp 82ndash94 2013

[36] R M Mitchum P R Vail and J B Sangree ldquoSeismic stratig-raphy and global changes of sea level Part 6 stratigraphicinterpretation of seismic reflection patterns in depositionalsequencesrdquo AAPG Memoir vol 62 pp 117ndash134 1977

[37] H Zhu X Yang X Zhou and K Liu ldquoThree-dimensionalfacies architecture analysis using sequence stratigraphy andseismic sedimentology example from the paleogene dongyingformation in the bz3-1 block of the bozhong sag Bohai BayBasin Chinardquo Marine and Petroleum Geology vol 51 pp 20ndash33 2014

[38] C M Burberry C A Jackson and S R Chandler ldquoSeismicreflection imaging of karst in the Persian Gulf Implications forthe characterization of carbonate reservoirsrdquo AAPG Bulletinvol 100 no 10 pp 1561ndash1584 2016

[39] P R Vail RMMitchum and R G Todd ldquoSeismic stratigraphyand global changes of sea levelrdquo AAPGMemoir vol 26 pp 49ndash212 1977

[40] Y F Gao H Fu T Wang H F Yang and L X Zhao ldquoThefeatures of ordovician sequence boundaries and its controls oncarbonate karst in tarim basinrdquoXinjiang PetroleumGeology vol33 no 10 pp 362ndash367 2015

[41] X Zhu H T Zhu H H Chen L Qi P J Li and L YunldquoCharacterization of hypogenic karst systems in the Middle-Lower Ordovician of Shunnan areaTarim Basinrdquo Oil and GasGeology vol 37 no 5 pp 653ndash662 2016

[42] A McDonnell R G Loucks and T Dooley ldquoQuantifying theorigin and geometry of circular sag structures in northern FortWorth Basin Texas paleocave collapse pull-apart fault systemsor hydrothermal alterationrdquo AAPG Bulletin vol 91 no 9 pp1295ndash1318 2007

[43] G R Davies and L B Smith Jr ldquoStructurally controlledhydrothermal dolomite reservoir facies an overviewrdquo AAPGBulletin vol 90 no 11 pp 1641ndash1690 2006

[44] P Eichhubl N C Davatzes and S P Becker ldquoStructural anddiagenetic control of fluidmigration and cementation along theMoab fault Utahrdquo AAPG Bulletin vol 93 no 5 pp 653ndash6812009

[45] E Frankowicz and K R McClay ldquoExtensional fault segmen-tation and linkages Bonaparte Basin outer North West ShelfAustraliardquo AAPG Bulletin vol 94 no 7 pp 977ndash1010 2010

[46] H J Yang K K Li W Q Pan Z Y Xiao and C F Cai ldquoBurialhydrothermal dissolution fluid activity and its transformingeffect on the reservoirs in Ordovician in Central Tarimrdquo ActaPetrologica Sinica vol 28 no 3 pp 783ndash792 2012

[47] G Wu H Yang S He S Cao X Liu and B Jing ldquoEffectsof structural segmentation and faulting on carbonate reservoirproperties a case study from the Central Uplift of the TarimBasin Chinardquo Marine and Petroleum Geology vol 71 pp 183ndash197 2016

[48] A Klimchouk A S Auler F H R Bezerra C L CazarinF Balsamo and Y Dublyansky ldquoHypogenic origin geologiccontrols and functional organization of a giant cave system inPrecambrian carbonates Brazilrdquo Geomorphology vol 253 pp385ndash405 2016

[49] Q Miao M Pan H L Gao and B Zhang ldquoThe 3-D visu-alization characterization of the complex buried-hill fracturestructurerdquo Xinjiang Petroleum Geology vol 29 no 21 pp 364ndash366 2008 (Chinese)

[50] W Q Pan Z M Wang C H Sun et al ldquoClassifications ofsequence boundaries in the Lower Paleozoic carbonates inTarim Basin and their significancesrdquo Oil and Gas Geology vol32 no 1 pp 531ndash541 2011

[51] Z H Kang ldquoThe karst paleogeomorphology of carbonatereservoir in Tahe Oilfieldrdquo Xinjiang Petroleum Geology vol 27pp 522ndash525 2006

[52] L D Wang Formation mechanics and distribution forecast ofCarbonates Paleokarst reservoir in T4

7Interface from Central

Tarim Basin [PhD thesis] PhD Dissertation in China Univer-sity of Geosciences Beijing China 2007

[53] S W Xie A Study on Sequence Stratigraphy and GeologicalCharacteristics for Yingshan Formation in the Central UpliftAera of Tarim Basin China [PhD thesis] PhD Dissertation inChengdu Univerisity of Technology 2011

[54] Z F ZhaiA Study on the Sequence stratigraphy and SedimentaryCharacteristic of Ordovician in Tazhong area of Tarim basin[PhD thesis] PhD Dissertation in Chengdu Univerisity ofTechnology 2012

[55] W Liu X Y Zhang and J Y Gu ldquoCorrosion inhibition andadsorption properties of methocarbamol on mild steel in acidicmediumrdquoPortugaliae ElectrochimicaActa vol 27 no 1 pp 435ndash442 2009

[56] C LWangGHWuW J Cui et al ldquoCharacteristics and distri-bution of intra-platform beach of the lower-middle ordovicianyingshan formation carbonaterdquo Acta Sedimentologica Sinicavol 29 pp 1048ndash1058 2011

[57] Z K Jin L Shi B S Gao and K H Yu ldquoCarbonate facies andfacies modelsrdquo Acta Sedimentologica Sinica vol 31 no 1 pp965ndash980 2013

[58] J H Zhang B S Yu Z L Qi Z K Bai Z Ruan and L RLi ldquoSeismic facies and the distribution of the intraplatformsholas in the Ordovician Yingshan Formation in the Ka-1three-dimensional seismic area Central TarimBasin XinjiangrdquoSedimentary Geology and Tethyan Geology vol 36 no 3 pp104ndash112 2016

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of


EarthquakesJournal of


Mining


Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal of

OceanographyInternational Journal of


Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering


GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of


OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in


MineralogyInternational Journal of


MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Geological ResearchJournal of


Geology Advances in

2 Geofluids

(a)

Kuqa Depression

Maigaiti slope

Tabei

Kongquehe

Southwest Depression Southeast

DepressionCentral

SoutheastUpliftUplift

Tianshan Mountain

Kunlun Mountain

Tazhong Uplift

0 200(km)

(km)

0 1000

N

TarimN

SN5

SN7SN6

SN1SN4

Shuntuoguole

Low uplift

Shuntuoguole

gentle slope

GuchengxuLow uplift

Khattak Uplift

0 20

FaultStructural boundaryWell location

Shunnan area

N

Slope

(b)

Boundary fault 1

Mangar sag

++

+

+

+

+

(km)

Peoplersquos

of ChinaRepublic

Uplift

Study area

83∘ 52

39∘

00

38∘

30

85∘ 23

Figure 1 Location of the Shunnan area in the Central Tarim Basin NW China (a) Location of the Tarim Basin in China and the Tazhonguplift in Tarim Basin (b) Main tectonic units of the Shunnan area

[7] Accordingly the principal difference between hypogenicand epigenic karst systems lies in the modes (confinedversus unconfined) and principal vectors (ascending versusdescending) of fluid circulation and in the source of rechargeto a given unit (recharge from depth versus recharge from theoverlying or immediately adjacent surface) [6 7]

There have been many case studies on carbonate karstover the past six decades but they deal mainly with epigenickarst systems (eg [8ndash14]) The progress on the charac-terization of the hypogenic karst systems (eg [15ndash19])predominantly focuses on the planar- or section-view delin-eations of lateral stratiform hypogenic karst system zonesand relevant fault system zones individually The ldquolateralstratiform hypogenic karst system zonerdquo is used to denote thezone where fluids are directed transversely flow across layersand formation and in which fluids related to upwelling flowsfrom the deep subsurface and upwards migrate along thefaults The relevant ldquofault system zonerdquo in this paper not onlydenotes the migration pathways (faults) of ascending fluidsthat contribute to the formation of hypogenic karst systembut also refers to the ldquocross-formational fault-vein hypogenickarst systemrdquo which is characterized by developing parallelaround faults

The Shunnan area is a three-level structural unit withinthe Tarim Basin located at the downthrown side of theboundary fault I of the Tazhong Low uplift (Figure 1) Itis bounded to the west by the Khattak Uplift north bythe Shuntuoguole Low uplift south by the Guchengxu Lowuplift and east by the Mangar sag (Figure 1) In recent yearshydrothermal minerals (calcite and quartz in veins and tab-ular anhydrites) at depths (gt6000m) and distinctive seismic

reflections that are expressed by a series of individual string-beads lateral spreading have been found in the Shunnan areaThese provide the potential conditions to characterize thedistribution of the hypogenic karst systems

The aim of this paper is to understand the spatial distribu-tion and controlling factors of hypogenic karst developmentand develop a model of the karst systems in the Middle-Lower Ordovician Yingshan Formation of Shunnan areaTarim Basin NW China In this paper the hypogenic karstsystems and faults were first distinguished on the basis ofan integrated approach of seismic data with available con-ventional cores wells and a scanning electron microscopeanalysis and then a new seismic characterization workflowwas developed including seismic amplitude thresholdingfault interpretation pickup andmerge display to enhance thedescription of the spatial distribution and coupled hypogenickarst systems and faults The proposed workflow will providenew insight into 3D seismic characterization of the hypogenickarst systems and can be used extensively in hypogenic-related karst basins around the world

2 Geological Setting

The Tarim Basin in western China (Figure 1) is a compositebasinwith a number of uplifts and depressions that developedas a result of a long and complicated tectonic history (eg[20ndash26]) It is located between the Tianshan Mountain andKunlun mountains occupying an area of 56 times 104 km2The basinrsquos east-west length is 1400 km while the maximumwidth reached 520 kmwith the altitude ranges between 800mand 1300m Collectively the development of the basinrsquos

Geofluids 3


Mid

dle-

Low

erO

rdov

icia

n

Yingshan

Yijianfang

Penglaiba


Arenite limestone

Dolomite

４74

４75

４76

４78

４80













4 Geofluids

Marls

Arenite limestone

Micrite limestone

6670 6671 6672 66736669

(g)(e)(d)(f)(c)(b)

(a)

Quartz


residual pore1 cm

(b)

Quartz


1 cm

(c)

Dolomite



quartz


1 cm

(d)


1 cm

(e)

Keatite

Residual pore

(f)

Slab plaster

(g)





Geofluids 5

+

+

A

Well location



SE(e)

SE(f)SN4(d)

0 2(km)

0 2(km)

0 2(km)

E


SN5SN6

0 4(km)Tw

o-w

ay tr

avel

tim

e (s)

Two-

way

trav

el ti

me (

s)

(b)


SE(a)

(c)

A

A

＄

BC

D

＄

B C D

+

+

+

+

+

+

+

+

+

50

40

50

35

４75

４76

４78

４80

４81

４74

４76

４78

４80

N

N

SN1

SN4SN6 SN7

SN5

0 8(km)

SN1

SN6 SN7

SN5








6 Geofluids

Mergedisplay

Faultinterpretation


Pickup

Pickup(a)

(b)

(c)

N

N

lateral

obli-que

Top

Seismic data

Z

X

Y

Z

XY

Z

XY

ZX

Y

Z

X

Y

25 km

2 km

1 km














Geofluids 7













8 Geofluids

SN4

Two-

way

trav

el ti

me (

s)

0 2(km)

E

50

40

++

++

+

SN1 SN5

SN6 SN7SN4

４74

４75

４76

４78

４80

(a)

Arenite limestone

Well location

Mud stone

Fluids

SN4

SN4Original system


2yj

1p

3

2

1

Lateral alteration

Karst cave

Dolomitic limestone

Limestone

Fault


Dolomite

Vertical alteration

Stratum

y11-2

y1-2

y21-2

(b)


Geofluids 9












10 Geofluids


Topographic lowland

Top BaseSQ2

SQ3

0 8(km)

SN7SN4SN5SN1

SN6Two-

way

trav

el ti

me (

s)

+

+

+

+ +

50

45

35

T74

T76

T75

T80

T78





Low

High


N

Low uplift

Low sag

Gentle slope

SN4

SN7

SN5

SN1SN6




Geofluids 11

30

(km)

Karst plain facies

Slope


Slump

Slump

SN7SN6

SN1 SN5SN4

N




+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘




8 Conclusions




12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 3


Mid

dle-

Low

erO

rdov

icia

n

Yingshan

Yijianfang

Penglaiba


Arenite limestone

Dolomite

４74

４75

４76

４78

４80













4 Geofluids

Marls

Arenite limestone

Micrite limestone

6670 6671 6672 66736669

(g)(e)(d)(f)(c)(b)

(a)

Quartz


residual pore1 cm

(b)

Quartz


1 cm

(c)

Dolomite



quartz


1 cm

(d)


1 cm

(e)

Keatite

Residual pore

(f)

Slab plaster

(g)





Geofluids 5

+

+

A

Well location



SE(e)

SE(f)SN4(d)

0 2(km)

0 2(km)

0 2(km)

E


SN5SN6

0 4(km)Tw

o-w

ay tr

avel

tim

e (s)

Two-

way

trav

el ti

me (

s)

(b)


SE(a)

(c)

A

A

＄

BC

D

＄

B C D

+

+

+

+

+

+

+

+

+

50

40

50

35

４75

４76

４78

４80

４81

４74

４76

４78

４80

N

N

SN1

SN4SN6 SN7

SN5

0 8(km)

SN1

SN6 SN7

SN5








6 Geofluids

Mergedisplay

Faultinterpretation


Pickup

Pickup(a)

(b)

(c)

N

N

lateral

obli-que

Top

Seismic data

Z

X

Y

Z

XY

Z

XY

ZX

Y

Z

X

Y

25 km

2 km

1 km














Geofluids 7













8 Geofluids

SN4

Two-

way

trav

el ti

me (

s)

0 2(km)

E

50

40

++

++

+

SN1 SN5

SN6 SN7SN4

４74

４75

４76

４78

４80

(a)

Arenite limestone

Well location

Mud stone

Fluids

SN4

SN4Original system


2yj

1p

3

2

1

Lateral alteration

Karst cave

Dolomitic limestone

Limestone

Fault


Dolomite

Vertical alteration

Stratum

y11-2

y1-2

y21-2

(b)


Geofluids 9












10 Geofluids


Topographic lowland

Top BaseSQ2

SQ3

0 8(km)

SN7SN4SN5SN1

SN6Two-

way

trav

el ti

me (

s)

+

+

+

+ +

50

45

35

T74

T76

T75

T80

T78





Low

High


N

Low uplift

Low sag

Gentle slope

SN4

SN7

SN5

SN1SN6




Geofluids 11

30

(km)

Karst plain facies

Slope


Slump

Slump

SN7SN6

SN1 SN5SN4

N




+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘




8 Conclusions




12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

4 Geofluids

Marls

Arenite limestone

Micrite limestone

6670 6671 6672 66736669

(g)(e)(d)(f)(c)(b)

(a)

Quartz


residual pore1 cm

(b)

Quartz


1 cm

(c)

Dolomite



quartz


1 cm

(d)


1 cm

(e)

Keatite

Residual pore

(f)

Slab plaster

(g)





Geofluids 5

+

+

A

Well location



SE(e)

SE(f)SN4(d)

0 2(km)

0 2(km)

0 2(km)

E


SN5SN6

0 4(km)Tw

o-w

ay tr

avel

tim

e (s)

Two-

way

trav

el ti

me (

s)

(b)


SE(a)

(c)

A

A

＄

BC

D

＄

B C D

+

+

+

+

+

+

+

+

+

50

40

50

35

４75

４76

４78

４80

４81

４74

４76

４78

４80

N

N

SN1

SN4SN6 SN7

SN5

0 8(km)

SN1

SN6 SN7

SN5








6 Geofluids

Mergedisplay

Faultinterpretation


Pickup

Pickup(a)

(b)

(c)

N

N

lateral

obli-que

Top

Seismic data

Z

X

Y

Z

XY

Z

XY

ZX

Y

Z

X

Y

25 km

2 km

1 km














Geofluids 7













8 Geofluids

SN4

Two-

way

trav

el ti

me (

s)

0 2(km)

E

50

40

++

++

+

SN1 SN5

SN6 SN7SN4

４74

４75

４76

４78

４80

(a)

Arenite limestone

Well location

Mud stone

Fluids

SN4

SN4Original system


2yj

1p

3

2

1

Lateral alteration

Karst cave

Dolomitic limestone

Limestone

Fault


Dolomite

Vertical alteration

Stratum

y11-2

y1-2

y21-2

(b)


Geofluids 9












10 Geofluids


Topographic lowland

Top BaseSQ2

SQ3

0 8(km)

SN7SN4SN5SN1

SN6Two-

way

trav

el ti

me (

s)

+

+

+

+ +

50

45

35

T74

T76

T75

T80

T78





Low

High


N

Low uplift

Low sag

Gentle slope

SN4

SN7

SN5

SN1SN6




Geofluids 11

30

(km)

Karst plain facies

Slope


Slump

Slump

SN7SN6

SN1 SN5SN4

N




+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘




8 Conclusions




12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 5

+

+

A

Well location



SE(e)

SE(f)SN4(d)

0 2(km)

0 2(km)

0 2(km)

E


SN5SN6

0 4(km)Tw

o-w

ay tr

avel

tim

e (s)

Two-

way

trav

el ti

me (

s)

(b)


SE(a)

(c)

A

A

＄

BC

D

＄

B C D

+

+

+

+

+

+

+

+

+

50

40

50

35

４75

４76

４78

４80

４81

４74

４76

４78

４80

N

N

SN1

SN4SN6 SN7

SN5

0 8(km)

SN1

SN6 SN7

SN5








6 Geofluids

Mergedisplay

Faultinterpretation


Pickup

Pickup(a)

(b)

(c)

N

N

lateral

obli-que

Top

Seismic data

Z

X

Y

Z

XY

Z

XY

ZX

Y

Z

X

Y

25 km

2 km

1 km














Geofluids 7













8 Geofluids

SN4

Two-

way

trav

el ti

me (

s)

0 2(km)

E

50

40

++

++

+

SN1 SN5

SN6 SN7SN4

４74

４75

４76

４78

４80

(a)

Arenite limestone

Well location

Mud stone

Fluids

SN4

SN4Original system


2yj

1p

3

2

1

Lateral alteration

Karst cave

Dolomitic limestone

Limestone

Fault


Dolomite

Vertical alteration

Stratum

y11-2

y1-2

y21-2

(b)


Geofluids 9












10 Geofluids


Topographic lowland

Top BaseSQ2

SQ3

0 8(km)

SN7SN4SN5SN1

SN6Two-

way

trav

el ti

me (

s)

+

+

+

+ +

50

45

35

T74

T76

T75

T80

T78





Low

High


N

Low uplift

Low sag

Gentle slope

SN4

SN7

SN5

SN1SN6




Geofluids 11

30

(km)

Karst plain facies

Slope


Slump

Slump

SN7SN6

SN1 SN5SN4

N




+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘




8 Conclusions




12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

6 Geofluids

Mergedisplay

Faultinterpretation


Pickup

Pickup(a)

(b)

(c)

N

N

lateral

obli-que

Top

Seismic data

Z

X

Y

Z

XY

Z

XY

ZX

Y

Z

X

Y

25 km

2 km

1 km














Geofluids 7













8 Geofluids

SN4

Two-

way

trav

el ti

me (

s)

0 2(km)

E

50

40

++

++

+

SN1 SN5

SN6 SN7SN4

４74

４75

４76

４78

４80

(a)

Arenite limestone

Well location

Mud stone

Fluids

SN4

SN4Original system


2yj

1p

3

2

1

Lateral alteration

Karst cave

Dolomitic limestone

Limestone

Fault


Dolomite

Vertical alteration

Stratum

y11-2

y1-2

y21-2

(b)


Geofluids 9












10 Geofluids


Topographic lowland

Top BaseSQ2

SQ3

0 8(km)

SN7SN4SN5SN1

SN6Two-

way

trav

el ti

me (

s)

+

+

+

+ +

50

45

35

T74

T76

T75

T80

T78





Low

High


N

Low uplift

Low sag

Gentle slope

SN4

SN7

SN5

SN1SN6




Geofluids 11

30

(km)

Karst plain facies

Slope


Slump

Slump

SN7SN6

SN1 SN5SN4

N




+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘




8 Conclusions




12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 7













8 Geofluids

SN4

Two-

way

trav

el ti

me (

s)

0 2(km)

E

50

40

++

++

+

SN1 SN5

SN6 SN7SN4

４74

４75

４76

４78

４80

(a)

Arenite limestone

Well location

Mud stone

Fluids

SN4

SN4Original system


2yj

1p

3

2

1

Lateral alteration

Karst cave

Dolomitic limestone

Limestone

Fault


Dolomite

Vertical alteration

Stratum

y11-2

y1-2

y21-2

(b)


Geofluids 9












10 Geofluids


Topographic lowland

Top BaseSQ2

SQ3

0 8(km)

SN7SN4SN5SN1

SN6Two-

way

trav

el ti

me (

s)

+

+

+

+ +

50

45

35

T74

T76

T75

T80

T78





Low

High


N

Low uplift

Low sag

Gentle slope

SN4

SN7

SN5

SN1SN6




Geofluids 11

30

(km)

Karst plain facies

Slope


Slump

Slump

SN7SN6

SN1 SN5SN4

N




+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘




8 Conclusions




12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

8 Geofluids

SN4

Two-

way

trav

el ti

me (

s)

0 2(km)

E

50

40

++

++

+

SN1 SN5

SN6 SN7SN4

４74

４75

４76

４78

４80

(a)

Arenite limestone

Well location

Mud stone

Fluids

SN4

SN4Original system


2yj

1p

3

2

1

Lateral alteration

Karst cave

Dolomitic limestone

Limestone

Fault


Dolomite

Vertical alteration

Stratum

y11-2

y1-2

y21-2

(b)


Geofluids 9












10 Geofluids


Topographic lowland

Top BaseSQ2

SQ3

0 8(km)

SN7SN4SN5SN1

SN6Two-

way

trav

el ti

me (

s)

+

+

+

+ +

50

45

35

T74

T76

T75

T80

T78





Low

High


N

Low uplift

Low sag

Gentle slope

SN4

SN7

SN5

SN1SN6




Geofluids 11

30

(km)

Karst plain facies

Slope


Slump

Slump

SN7SN6

SN1 SN5SN4

N




+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘




8 Conclusions




12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 9












10 Geofluids


Topographic lowland

Top BaseSQ2

SQ3

0 8(km)

SN7SN4SN5SN1

SN6Two-

way

trav

el ti

me (

s)

+

+

+

+ +

50

45

35

T74

T76

T75

T80

T78





Low

High


N

Low uplift

Low sag

Gentle slope

SN4

SN7

SN5

SN1SN6




Geofluids 11

30

(km)

Karst plain facies

Slope


Slump

Slump

SN7SN6

SN1 SN5SN4

N




+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘




8 Conclusions




12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

10 Geofluids


Topographic lowland

Top BaseSQ2

SQ3

0 8(km)

SN7SN4SN5SN1

SN6Two-

way

trav

el ti

me (

s)

+

+

+

+ +

50

45

35

T74

T76

T75

T80

T78





Low

High


N

Low uplift

Low sag

Gentle slope

SN4

SN7

SN5

SN1SN6




Geofluids 11

30

(km)

Karst plain facies

Slope


Slump

Slump

SN7SN6

SN1 SN5SN4

N




+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘




8 Conclusions




12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 11

30

(km)

Karst plain facies

Slope


Slump

Slump

SN7SN6

SN1 SN5SN4

N




+

+

++

++

20100

30

00

3000 0030

39∘

39∘

84∘ 84∘ 85∘ 85∘




8 Conclusions




12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

12 Geofluids




Acknowledgments


References































Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 13








































Mining


Journal of









Journal of




Advances in











Geology Advances in








Mining


Journal of









Journal of




Advances in











Geology Advances in

seismic characterization of hypogenic karst systems...

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