research article laboratory measurement and interpretation...

Research ArticleLaboratory Measurement and Interpretation of the Changes ofPhysical Properties after Heat Treatment in Tight Porous Media

Yili Kang Mingjun Chen Lijun You and Xiangchen Li

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum University Chengdu 610500 China

Correspondence should be addressed to Mingjun Chen chenmj1026163com

Received 25 September 2014 Accepted 30 December 2014

Academic Editor Sachin Jangam

Copyright copy 2015 Yili Kang et alThis is an open access article distributed under the Creative CommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Prevention of water blocking and optimization of multiscale flow channels will increase gas production of tight reservoirs Physicalproperties of samples from representative tight gas reservoirs were measured before and after high temperature treatment Resultsshow that with the increase of treatment temperaturemass decreases acoustic transit time increases and permeability and porosityincrease Permeability begins to increase dramatically if treatment temperature exceeds the threshold value of thermal fracturingwhich is 600sim700∘C 500sim600∘C 300sim500∘C and 300sim400∘C for shale mudstone tight sandstone and tight carbonate rockrespectively Comprehensive analyses indicate that the mechanisms of heat treatment on tight porous media include evaporationand dehydration of water change of mineral structure generation of microfracture and network connectivity Meanwhile fieldimplementation is reviewed and prospected Interpretations indicate that according to the characteristics of multiscale masstransfer in tight gas formation combining heat treatment with conventional stimulation methods can achieve the best stimulationresult

1 Introduction

Tight gas reservoirs including shale gas tight sandstone gasand tight carbonate gas reservoirs are playing an increasinglyimportant role in the growth of natural gas reserves andenergy supply Gas production from tight gas reservoir is aprocess of multiscale mass transfer In order to maximizethe ability of gas production it is necessary to optimize allthe scales of mass transfer [1ndash4] Single hydraulic fracturingmainly generates great-scale fractures based on preexistingfractures but for tight gas reservoir many of the reservesoccur in small-scale pores Meanwhile in order to maximizefracture propagation much more fracturing fluid is requiredto be pumped into formation If the fluid system containsfresh water the potential of clay swelling and migrationwould be extremely high Considering that huge volume ofliquid into formation is very difficult to flow back from thepores which have the ultrasmall volume and poor connec-tivity various types of formation damage would be easilyinduced and the production cannot be satisfactory [5ndash7]

Therefore effectiveness of conventional stimulation methodis still not so good for tight gas reservoirs A certain kind ofstimulationmethod is urgent to be developed and formationheat treatment based on thermal property of rock is devel-oped as an innovative well stimulation technique which isfocused on prevention of water blocking and generation orpropagation of small-scale fractures

Formation heat treatment which is recognized as a state-of-the-art technology for near-wellbore formation [8] mightplay a significant role in well stimulation On the one handthe water in pores would be removed perfectly due to theevaporation or dehydration of water at high temperatureTherefore formation damage like water blocking could beprevented and permeability of rock is enhanced by remov-ing water in gas flow channel [9ndash11] On the other handinduced fracture generates preexisting fracture propagatesand finally various kinds of fractures connect to be networkunder the action of thermal stress at high temperature [12ndash14] As a result the ability of mass transfer can be enhanceddramatically through formation heat treatment Compared

Hindawi Publishing CorporationJournal of ChemistryVolume 2015 Article ID 341616 10 pageshttpdxdoiorg1011552015341616

2 Journal of Chemistry

with conventional stimulation methods like hydraulic frac-turing and acid treatment the advantages of formation heattreatment mainly consist in the following

(1) It prevents water blocking by evaporation of blockedwater and dehydration of clay structure [15]

(2) It enhances permeability and porosity in microscaleuniformly Meanwhile it makes anisotropy of rock inmesoscale and macroscale under control

(3) It accelerates desorption and diffusion of methane inmatrix especially for rocks rich in organic [16]

(4) Formation heat treatment does not need water sourceand it also does not contaminate groundwater It istotally eco-friendly

However systematic studies on heat treatment are stillrare and the application on stimulation of tight gas formationis urgent to understand The previous studies on formationheat treatment are based on sandstone and samplesrsquo perme-ability is relatively high [8 9 15 17] Also thermal crackingin rock which has been studied a lot in nuclear waste storagemining technique HDR geothermal extraction and stabilityanalysis of constructions is mostly based on granite thatis not the natural gas reservoir [13 18ndash21] Therefore theeffect of high temperature on tight gas reservoirs which isimportant in the development of petroleum industry needsto be evaluated Furthermore the effect of heat treatmenton different kinds of tight rocks also still needs to be distin-guished In this work samples from the representative tightgas reservoirs were treated under high temperature in argongas environment to simulate the in situ anoxic conditionSeveral lab experimental methods were comprehensivelyutilized to investigate the effect of heat treatment on physicalproperties of tight rocks Then the essence of the changesof physical properties for tight rocks after heat treatmentis analyzed comprehensively Lastly field implementation ofheat treatment process is discussed

2 Experimental Sample and Procedure

21 Samplesrsquo Description Tight rock samples in this study aretaken from three kinds of representative tight gas reservoirsShale samples are from the Longmaxi formation of LowerSilurian in Sichuan Basin which is recognized as the mostproducible and profitable shale gas reservoir in China Tightsandstone samples are from Upper Palaeozoic in Permianin Ordos Basin which is the most giant tight sandstone gasreservoir in China And the tight carbonate rock sample isfrom Feixianguan formation of Lower Triassic in northeastSichuan Basin which is the representative tight carbonategas reservoir in China Meanwhile in order to investigatethe influence of organic matter in thermal process mudstonesamples from Sichuan Basin are selected to be compared withshale samples These reservoirs are typically characterizedby various kinds of pore types complicated pore struc-ture and strong heterogeneity Porosity and permeabilitywere measured by CMS-300 Core-Automatic DeterminationInstrument for permeability more than 001 times 10minus3 120583m2 and

by LGPM700 with transient pulse decay method for perme-ability less than 001 times 10minus3 120583m2 Initial physical propertiesof these samples under conventional conditions (435 psi and20∘C) are presented in Table 1

22 Experimental Temperature Setting X-ray diffraction(XRD) analyses of these samples show that clay mineral andquartz are the main minerals (Table 2) except that tightcarbonate rock is mainly composed of dolomite The clayminerals of samplesmainly consist of illite chlorite kaoliniteand mixed-layer mineral of illitesmectite except that shaledoes not contain kaolinite Within a certain temperaturerange structure of clay minerals would be destroyed Besidesclay minerals thermal reactions can occur in other mineralconstituents such as quartz and carbonate Particularly thequartz which has a volume expansion of 27 in 2sim5 secondswhen temperature elevates to 573∘C due to the 120572 rarr 120573inversion of quartz has a dominant effect on themagnitude ofthermal expansion [19 22] Heats of reaction for several mainminerals of samples are concluded in Table 3 According tothe temperature range of heat reaction for minerals shown inTable 3 various temperature values that is 100 200 300 400500 600 700 and 800∘C were specified as the temperatureset-points to evaluate the effect of heat treatment on physicalproperties of tight rocks

23 Experimental Equipment andMethods In order to simu-late the in situ anoxic condition samples with correspondingirreducible water saturation were mounted in a tube furnacefilled with argon gas Mass of samples was measured beforeand after heat treatment by precision electronic balance ina controlled humidity oven at 20∘C and 0RH Acousticcompressional wave (P-wave) and shearwave (S-wave) transittime were measured before and after heat treatment underconventional conditions (435 psi and 20∘C) through SCMS-J Acoustics-Resistivity Measurement Equipment which isresearched and developed independently by the State KeyLaboratory of Oil and Gas Reservoir Geology and Exploita-tion of SWPU and the frequency of ultrasonic wave is170 kHz Porosity and permeability weremeasured before andafter heat treatment through CMS-300 for permeability morethan 001times10minus3 120583m2 and through LGPM700 for permeabilityless than 001 times 10minus3 120583m2 under conventional conditions(435 psi and 20∘C)

As is shown in Figure 1 the testing procedures are asfollows

(1) Measure one samplersquos mass acoustic transit timeand porosity and permeability under the conditionsshown above

(2) Mount the sample in the tube furnace Fully evacuatethe sample at 62∘C to ensure that air includingadsorbed gas is excluded from the rock Then breakvacuum with argon gas until ambient pressure ofsample returns to atmospheric pressure

(3) Heat the sample to 100∘C at a rate of 5∘Cminstarting with atmospheric temperature (20∘C) Whentemperature in tube furnace is up to 100∘C the testingtemperature would be maintained for 2 h and then

Journal of Chemistry 3

Table 1 Physical properties of samples without any heat treatment

Sample number Mass119872

0

gLength119871

0

cmDiameter119863

0

cmPorosityΦ

0

Permeability119870

0

10minus3 um2

P-wave transittime Δ119879

119901

120583smS-wave transittime Δ119879

119904

120583sm Lithology

Shale1 633463 5400 2504 35 000780 2212963 3766667 ShaleShale2 670235 7396 2482 46 00256 2459438 4088697 ShaleShale3 429417 4966 2500 47 00947 2478856 4325413 ShaleShale4 642955 6040 2500 38 00860 2326159 3900662 ShaleSand1 410425 3252 2502 73 00167 2873846 4289231 SandstoneSand2 660089 5268 2478 46 00181 2090288 3839150 SandstoneSand3 595467 4650 2506 58 00465 2740964 4569707 SandstoneSand4 601367 4862 2504 83 00571 3289420 5236723 SandstoneSand5 638542 5308 2488 88 00539 2693178 4210328 SandstoneCarbonate 558123 3958 2496 43 00135 1602629 3119312 CarbonatiteMud1 449856 4210 2482 53 00323 3587732 4824061 MudstoneMud2 468326 4196 2484 31 000711 3228422 5398188 MudstoneMud3 376457 3392 2488 23 000559 4156342 6884956 Mudstone

Table 2 Quantitative analyses of minerals by XRD

Lithology Content of minerals Clay mineral Quartz K-feldspar Anorthose Calcite Dolomite Siderite Pyrite

Shale 3996 4115 312 512 291 411 000 363Sandstone 2490 7289 001 013 206 001 000 000Carbonatite 790 770 467 293 000 7680 000 000Mudstone 5652 1114 000 704 2530 000 000 000

Table 3 Heats of reaction for several minerals [34 35]

Minerals Temperature range ∘C Reaction after heat treatmentIllite and clay mica 125sim250 Loss of hydroscopic waterMg-chlorite 650 14 A spacing is intensifiedFe-chlorite 500 14 A spacing less intense becoming broad and diffuseMixed-layer clays lt600 Varies with amounts and types of minerals presentKaolinite well crystallized 575sim625 Replacement by amorphous metakaolinQuartz 573 120572 rarr 120573 inversionCa-carbonate 700ndash830 Decomposition

CMS-300 LGPM700

Precision electronic balance

Controlled humidityoven

Oscilloscope

Acousticreceiver probe

Acoustictransmitter probe

Acoustic signal source

Sample

(SCMS-J)Tube furnace

Sample

pump

Pressuregauge

Controlvalve

Argon gas source Vacuum

Figure 1 Schematic diagram of the experimental apparatus


decreases to the atmospheric temperature with a rateof 5∘Cmin

(4) Measure the mass acoustic transit time and porosityand permeability through the same methods andconditions of the first procedure

(5) Repeat the above steps with heating temperatures of200 300 400 500 600 700 and 800∘C respectivelyDuring the whole process of the heat treatment thesample is always in argon gas atmosphere

3 Experimental Results

31 Effect of Heat Treatment on Mass Change of mass afterheat treatment mainly reflects the loss of free water adsorbedwater interlayer water and constitution water As is shownin Figure 2 mass of samples tends to decrease as treatmenttemperature increasesMeanwhile the evident abrupt changeof mass occurs at temperature lower than 200sim300∘C withtemperature increasingThemass is substantially unchangingif temperature is higher than that range

Change of mass varies in different lithologies Mudstoneis the most affected After heat treatment under 800∘C itsmass decreases as much as 238 on average compared withthat before any heat treatmentMagnitude ofmass decrease is185 for shale 055 for tight sandstone and 010 for tightcarbonate rock

32 Effect of Heat Treatment on Acoustic Transit Time The-oretically acoustic transit time could increase if the porousmedia become less tight Since evaporation or dehydrationof water phase and thermal-induced fracturing are the mostimportant mechanisms of heat treatment change of theacoustic transit time in this work mainly reflects the changeof pore structure Experimental results show that transit timefor both compressional wave (P-wave Δ119879

119901) and shear wave

(S-wave Δ119879119904) tends to increase as temperature increases

(Figure 3) but the change is not very remarkable as wellas the change of porosity presented below Comparing theacoustic transit time after heat treatment at 800∘C with thatbefore heat treatment Δ119879

119901and Δ119879

119904increase as much as 119

times and 114 times for shale 162 times and 155 times fortight sandstone 110 times and 117 times for tight carbonaterock and 113 times and 118 times for mudstone

Since the responses of Δ119879119901and Δ119879

119904to temperature are

different ratio of Δ119879119904to Δ119879

119901(Δ119879119904Δ119879119901) is necessary to be

concerned with in order to comprehensively analyze theeffect of heat treatment on physical properties such as poresize and fracture propagation [23] Outcome of the acoustictransit timemeasurement shows that change ofΔ119879

119904Δ119879119901does

not have obvious regularity as the treatment temperatureincreases (Figure 4) Compared with Δ119879

119904Δ119879119901without any

heat treatment the value after heat treatment at 800∘C hasa tendency of increase for shale and most of tight sandstonesamples but for tight carbonate rock and most of mudstonesamples it has a tendency of decrease

33 Effect of Heat Treatment on Permeability and PorosityIn general permeability is one of the physical properties

094

095

096

097

098

099

100

0 200 400 600 800

Shale1 Shale2 Shale3Shale4 Sand1 Sand2Sand3 Sand4 Sand5Carbonate Mud1 Mud2Mud3

MiM

0

T (∘C)

Figure 2 Normalized mass as a function of treatment temperaturefor all the samples

0

05

1

15

2

25Sh

ale1

Shal

e2

Shal

e3

Shal

e4

Sand

1

Sand

2

Sand

3

Sand

4

Sand

5

Carb

onat

e

Mud

1

Mud

2

Mud

3

ΔTp

ΔTs

ΔT

800∘C

ΔT

20∘C

Figure 3 Ratio of acoustic transit time at 800∘C to that at 20∘C forall the samples

that engineers are most concerned about The permeabilitychange caused by heat treatment is presented in Figure 5 Per-meability tends to increase with the treatment temperaturegetting higher What is more permeability has an evidentabrupt change within a certain temperature range In detailif temperature is lower than the threshold value increase ofthe permeability is not so obvious and if the temperature ishigher than the threshold value significant increase of thepermeability occurs Chen et al (1999) recognized that per-colation model could describe that change behavior perfectly[18]

Meanwhile the variation of permeability by heat treat-ment is not the same for different lithologies For the thresh-old temperature shale is 600sim700∘C tight sandstone is 300sim500∘C tight carbonate rock is 300sim400∘C and mudstone is


0

05

1

15

2

25Sh

ale1

Shal

e2

Shal

e3

Shal

e4

Sand

1

Sand

2

Sand

3

Sand

4

Sand

5

Carb

onat

e

Mud

1

Mud

2

Mud

3

ΔT

sΔ

Tp

ΔTsΔTp at 800∘CΔTsΔTp at 20∘C

Figure 4 Ratio of Δ119879119904

to Δ119879119901

at 20∘C and 800∘C for all the samples

0

10

20

30

40

50

60

70

80

90

0 100 200 300 400 500 600 700 800


T (∘C)

KiK

0

Figure 5 Normalized permeability as a function of treatment tem-perature for all the samples

500sim600∘C Compared with permeability without any heattreatment the permeability of samples after 800∘C treatmentincreases as much as 1053sim3684 times (2418 times onaverage) for shale 1463sim3355 times (2192 times on average)for tight sandstone 1134 times for tight carbonate rock and1211sim8036 times (5347 times on average) for mudstone

Effect of heat treatment on porosity is similar to that onpermeability (Figure 6) It still has an abrupt increase withina specified temperature range which is nearly the same asthe change of permeability In detail as the treatment tem-perature elevates increase of porosity is relatively slow if thetemperature is lower than that range but when temperatureexceeds that range the porosity has a relatively large increaseHowever the increase of porosity is not as remarkable as thatof permeability and it also does not have a very evidently

05

10

15

20

25

30

35

40

45

0 100 200 300 400 500 600 700 800


T (∘C)

ΦiΦ

0

Figure 6 Normalized porosity as a function of treatment tempera-ture for all the samples

abrupt change within a range of threshold temperatureMeanwhile the variation of porosity is not the same fordifferent lithologies Compared with porosity without anyheat treatment the porosity of samples after heat treatmentat 800∘C increases as much as 185sim214 times (195 times onaverage) for shale 161sim287 times (203 times on average)for tight sandstone 215 times for tight carbonate rock and158sim405 times (282 times on average) for mudstone

4 Discussions

Tight gas reservoir has characteristics such as relatively smallpore richness in clay minerals or fragile minerals complexflow paths and serious anisotropy [24 25] Meanwhilepotential water blocking is quite easy to occur and difficultto prevent from the initial drilling and completion of wellboreto the depletion of reservoir during production According tothe experimental results shown above physical properties ofsamples change remarkably after high temperature treatmentIt is necessary to investigate mechanisms of the changes ofphysical properties

41 Evaporation and Dehydration of Water Phase Althoughthe free water phase in pore can be easily excluded at about100∘C other water phases that is adsorbed water interlayerwater and constitution water that exist within minerals arenot easily excluded [26] Generally speaking if temperatureincreases to 100sim200∘C adsorbed water and interlayer watercan be excluded and constitution water in lattice can beexcluded if the temperature is increased to 400sim800∘C Themain reason for mass decrease in the experiment is theexclusion of adsorbedwater and interlayerwater Evaporationand dehydration of water phase in pores expand the gas flowchannel and then permeability increases


Meanwhile the dehydration of constitution water in clayminerals can make the newly generated minerals tighterand strengthen fragility of rock which could be recognizedas the function of consolidation and would accelerate theeffectiveness of hydraulic fracturing [27 28] Besides if theheating rate is high enough such as microwave heating [1]instant evaporation of interlayer water would occur to makethe mineral crystal fracture in the middle and separate fromthe edge of particle which would generate microfracture andenhance the permeability evidently

42 Mineral Phase Change and Decomposition at High Tem-perature As is shown in Table 3 some physical or chemicalreactions occur when the minerals absorb a certain amountof heat The most consistent reaction is the inversion ofquartz from the 120572 rarr 120573 inversion at 573∘C The amountof heat needed to complete this inversion is known to be4825 calgm [29] The phase is fully reversible so uponcooling an equivalent amount of heat is liberatedThe reasonof highlighting the phase change of quartz is that quartz has aquick (2sim5 seconds) volume expansion of 27 when quartzis heated to 573∘C which can easily cause the strong thermal-induced stressTherefore when samplersquos temperature reaches573∘C it is prone to some degree of break

43 Thermal-Induced Fracturing Although thermal fractur-ing of rock has minor influence on bulk volume or density ithas a significant effect on pore structure mainly reflected asgeneration and propagation of fracture As rock is made up ofdifferent kinds of minerals differences in thermal expansionof different minerals and differences in thermal expansionalong different crystallographic axes of the same mineral canresult in heterogeneity and anisotropy of thermal expansionwhich generate thermal-induced stress [22] Besides if tem-perature gradient exists in rock thermal expansion must bedifferent in every part of rock even though thermal expansioncoefficient of each mineral is the same which could alsogenerate thermal stress

If thermal stress exceeds the ultimate tensile strength(tensile strength or compressive strength) at somewhere ofthe rock microfracture would occur Also different heatingrate and interval can cause different degree of thermal fractur-ing Generally speaking thermal fracturing tends to occur inthe short axis direction of mineral particles [30] Thereforewhen temperature is relatively low intercrystalline fractureis the main result of thermal fracturing and as temperatureincreases intracrystal fracture and transcrystalline fracturebegin occurring [31]

According to the permeability measurement results after800∘C treatment permeability of samples increases as muchas 2418 times on average for shale 2192 times on averagefor tight sandstone 1134 times for tight carbonate rock and5347 times on average for mudstone In order to detectthe mechanism of permeability enhancement caused by thegeneration of fracture SEM (scanning electron microscopy)imaging was conducted before and after 800∘C treatmentrespectively Meanwhile to image themicrostructure of shalemore clearly argon-ion milling was utilized to produce amuch flatter surface As is shown in Figure 7 various kinds of

fractures were initiated or propagated after 800∘C treatmentMeanwhile SEM images show that thermal-induced frac-tures are generated in different scales depending on thermalexpansion of different minerals These fractures increasepermeability remarkably

44 Comprehensive Mechanisms of High Temperature Treat-ment Comprehensive analyses of the above mechanismsindicate that essence of the changes of physical propertiesfor tight rock after high temperature treatment is a set ofmultiscale processes involving evaporation and dehydrationof water phase change of mineral structure and generationof fracture network As is presented in Figure 8 the red arrowrepresents the process of thermal fracturing which producesmicrofractures from initiation and propagation to networkconnectivity

According to the experimental results of permeabilitychange permeability has an evident abrupt change within acertain temperature range which can be recognized as therange of threshold value based on percolation model If thetemperature is lower than the threshold value effect of heattreatment is mainly reflected in evaporation or dehydrationof water phase and minor generation of microfractures Itsmain mechanism is to prevent water blocking in pores but itcannot enhance permeability of tight rock essentially There-fore the main mechanism of permeability enhancementthrough heat treatment is the fracture network developedfrom initiation of microfracture and fracture propagationunder the action of thermal stress when the treatmenttemperature is higher than the threshold value Furthermorekerogen in shale can strengthen the action of thermal stresscompared to others without any organic materials In detailthe kerogen would generate large amount of gas and oilyproduct at certain high temperature and when it is heatedthese productswould expand seriously resulting in extendingpressure [32] If the value of extending pressure exceeds acertain critical value the rock would develop more dramaticfracturing

5 Prospects on Field Testing

The concept of formation heat treatment was first proposedby Jamaluddin et al (1995) to solve formation damageinduced by water blocking which mainly aimed at relativelyhigh permeability samples compared with the samples in thiswork [8] For the application in industry the earliest reportwas that of Albaugh (1954) on an oil well in California whichhad an increase of 76 in production compared with that ofpretreatment [33] The other typical application in industrywas that of Jamaluddin et al (1999) on a field test that wascarried out in a disused gaswell whichmade the permeabilityincrease from 066 times 10minus3 120583m2 to 20 times 10minus3 120583m2 [17]

Since the high temperature has the risk of destroyingcasingcement integrity it needs to be considered in fieldapplication Many excellent ideas have been presented suchas that of Jamaluddin et al (1999) who designed andconstructed an electrical down-hole heater by using high-pressure nitrogen gas as the heat carrier [17] What is moreseveral other ways to transport heat to objective formation


Before heat treatment After heat treatment

(a) Shale


(b) Tight sandstone


(c) Tight carbonate rock


(d) Mudstone

Figure 7 SEM of samples showing thermal-induced fractures after 800∘C treatment


Table 4 Contribution of various stimulation methods on different scales of mass transfer

Scale Formation heat treatment Hydraulic fracturing Gas-based fracturing Acid treatment Acid fracturing119878

119908

decrease 995333995333995333995333 e f e eMineral reaction 995333995333995333995333 f f 995333995333995333 995333995333995333

Microfracture generation 995333995333995333995333 995333995333 995333995333 f 995333995333

Mesomacrofracture generation 995333995333 995333995333995333995333 995333995333995333995333 f 995333995333995333995333

995333995333995333995333 predominant995333995333995333 secondary995333995333 weak f ineffective and e harmful

Evaporation

Dehydration

Quartzphase change

Minerals decomposition

Fracture network

Water phase

Mineral

Rock

Temperature

Scal

e

DehydrationPhase change

Decomposition

Thermal-inducedfracturing

Evaporation

200∘C573∘C

Ambient temperature

100∘C

400∘C

Figure 8 Mechanisms of heat treatment for tight rocks

point such asmicrowave [1] andhigh-power laser technology[20] are still very effective These heating methods are alldesigned and constructed to enhance permeability mostremarkably and avoid destroying the casingcement integrityMeanwhile in order to heat the target depth accuratelycoiled tubing system would be a very good choice Also thetechnology of coiled tubing is applicable in horizontal wellwhich can meet the requirement of staged stimulation inhorizontal well

Gas production of tight reservoirs is a typical multiscalemass transfer process which is related to decrease of watersaturation (119878

119908) change of mineral structure and generation

and propagation of microfracture and mesomacrofractureTable 4 summarizes the contribution of different stimula-tion methods that is formation heat treatment hydraulicfracturing gas-based fracturing acid treatment and acidfracturing on the above four scales Compared with otherstimulation methods the advantages of heat treatment aremainly reflected in the scale of reducing 119878

119908and genera-

tion of microfracture The development of large amount ofmicrofracture plays an important role in reducing fracturingpressure and generating fracture network for tight rock

Generally speaking gas production of tight reser-voirs contains processes of desorption diffusion and slipflow Therefore only if the matrix pore microfractureand mesomacrofracture were suitably matched could thehighest production be achieved Conventional stimulationmethod such as hydraulic fracturing mainly plays an impor-tant role in the propagation of mesomacrofracture and

heat treatment method mainly works in the development ofmicrofracture and prevention of water blocking Thereforecombining heat treatment stimulation and other nonthermalstimulations can perfectly match all the scales of mass trans-port processes resulting in the most effective stimulation

6 Conclusions

In this work physical properties after heat treatment fordifferent lithologies are studied experimentally MeanwhileSEM imaging was implemented to detect microfracturedevelopment and other structural changes Since formationheat treatment is a state-of-the-art technology for tight gasformation and the systematic studies are still in the infancyresults of this work are significant to deeply understand theadvantage of heat treatment on gas production enhancementConclusions from this work are summarized as follows

(1) Physical properties of tight rocks change signifi-cantly after specified temperature treatment Gen-erally speaking shale and mudstone change moreremarkably than tight sandstone and tight carbonaterock

(2) The decrease of mass mainly occurs lower than 200sim300∘C Acoustic transit time increases as temperatureincreases except that the change of Δ119879

119904Δ119879119901does

not have obvious regularity As temperature increasespermeability of shale mudstone tight sandstoneand tight carbonate rock increases remarkably at


600sim700∘C 500sim600∘C 300sim500∘C and 300sim400∘Crespectively which is the threshold temperature rangeof thermal fracturing for each lithology

(3) Essence of the changes of physical properties afterheat treatment for tight rock is a set of multiscaleprocesses involving evaporation and dehydration ofwater phase change of mineral structure and gener-ation of fracture network

(4) Typical field applications are reviewed to confirmthe feasibility of heat treatment in industry Heat-ing methods such as high-pressure nitrogen andmicrowave are presented to be effective in enhancingpermeability remarkably and avoiding destroying thecasingcement integrity

(5) Heat treatment can dramatically enhance permeabil-ity in the scale of matrix pore and microfractureHowever for the scale of mesomacrofracture it isnecessary to use conventional stimulation methodTherefore integrating heat treatment with conven-tional stimulation might be the best choice

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Basic ResearchProgram of China (2010CB226705) China Scholarship Fundand Open Fund (PLN1117) of the State Key Laboratory ofOil and Gas Reservoir Geology and Exploitation (SouthwestPetroleum University)

References

[1] G Li Y F Meng and H M Tang ldquoClean up water blockingin gas reservoirs by microwave heating laboratory studiesrdquo inProceedings of the International Oil amp Gas Conference and Exhi-bition in China Paper SPE 101072 Beijing China December2006

[2] F Javadpour D Fisher and M Unsworth ldquoNanoscale gasflow in shale gas sedimentsrdquo Journal of Canadian PetroleumTechnology vol 46 no 10 pp 55ndash61 2007

[3] S A Najeeb A KMohammed K Hossein andM G RamonaldquoPhysics and modeling of gas flow in shale reservoirsrdquo in Pro-ceedings of the Abu Dhabi International Petroleum Conferenceand Exhibition Paper SPE 161893 pp 2822ndash2836 Abu DhabiUAE November 2012

[4] J Cai E Perfect C-L Cheng and X Hu ldquoGeneralizedmodeling of spontaneous imbibition based on hagen-poiseuilleflow in tortuous capillaries with variably shaped aperturesrdquoLangmuir vol 30 no 18 pp 5142ndash5151 2014

[5] D B Bennion F B Thomas R F Bietz and D W BennionldquoWater and hydrocarbon phase trapping in porous mediamdashdiagnosis prevention and treatmentrdquo Journal of CanadianPetroleum Technology vol 35 no 10 pp 29ndash36 1996

[6] L J You and Y L Kang ldquoIntegrated evaluation of waterphase trapping damage potential in tight gas reservoirsrdquo in

Proceedings of the 8th European Formation Damage ConferencePaper SPE 122034 Scheveningen The Netherlands May 2009

[7] J Cai and S Sun ldquoFractal analysis of fracture increasingspontaneous imbibition in porous media with gas-saturatedrdquoInternational Journal of Modern Physics C vol 24 no 8 ArticleID 1350056 2013

[8] A K M Jamaluddin M Vandamme and B K Mann ldquoFor-mation heat treatment (FHT) a state-of-the-art technology fornear-wellbore formation damage treatmentrdquo Paper SPE 95-67presented at the Annual Technical Meeting Calgary AlbertaCanada June 1995

[9] A KM Jamaluddin D B Bennion F BThomas and T YMaldquoApplication of heat treatment to enhance permeability in tightgas reservoirsrdquo Journal of Canadian Petroleum Technology vol39 no 11 pp 19ndash24 2000

[10] J C Cai and BM Yu ldquoA discussion of the effect of tortuosity onthe capillary imbibition in porous mediardquo Transport in PorousMedia vol 89 no 2 pp 251ndash263 2011

[11] F Meng P Zhong Z Li X Cui and H Zheng ldquoSurfacestructure and catalytic performance of Ni-Fe catalyst for low-temperature CO hydrogenationrdquo Journal of Chemistry vol2014 Article ID 534842 7 pages 2014

[12] C Yong and C-YWang ldquoThermally induced acoustic emissionin westerly graniterdquo Geophysical Research Letters vol 7 no 12pp 1089ndash1092 1980

[13] Y Zhao Z Wan Y Zhang et al ldquoExperimental study ofrelated laws of rock thermal cracking and permeabilityrdquoChineseJournal of Rock Mechanics and Engineering vol 29 no 10 pp1970ndash1976 2010

[14] H Tian T Kempka N X Xu and M Ziegler ldquoPhysicalproperties of sandstones after high temperature treatmentrdquoRock Mechanics and Rock Engineering vol 45 no 6 pp 1113ndash1117 2012

[15] A K M Jamaluddin L M Vandamme T W Nazarko andD B Bennion ldquoHeat treatment for clay-related near wellboreformation damagerdquo Journal of Canadian Petroleum Technologyvol 37 no 1 pp 56ndash63 1998

[16] C R Hartman J R Ambrose I Y Akkutlu and C R ClarksonldquoShale gas-in-place calculations part IImdashmulticomponent gasadsorption effectsrdquo inProceedings of theNorthAmericanUncon-ventional Gas Conference and Exhibition Paper SPE 144097TheWoodlands Tex USA June 2011

[17] A K M Jamaluddin M Hamelin K Harke and H McCaskillldquoField testing of the formation heat treatment processrdquo Journalof Canadian Petroleum Technology vol 38 no 3 pp 38ndash451999

[18] Y Chen X D Wu and F Q Zhang ldquoExperimental study ofrock thermal crackingrdquo Chinese Science Bulletin vol 44 no 8pp 880ndash883 1999

[19] M G Keaney C Jones P Meredith and S Murrell ldquoThermaldamage and the evolution of crack connectivity and permeabil-ity in ultra-low permeability rocksrdquo in Proceedings of the 6thNorth America Rock Mechanics Symposium Paper ARMA 04-537 Houston Tex USA June 2004

[20] R M Graves and E T Bailo ldquoAnalysis of thermally altered rockproperties using high-power laser technologyrdquo in Proceedingsof the Canadian International Petroleum Conference CalgaryCanada June 2005

[21] T Mehmannavaz M Ismail S Radin Sumadi M A RafiqueBhutta M Samadi and S M Sajjadi ldquoBinary effect of fly ashand palm oil fuel ash on heat of hydration aerated concreterdquoThe


Scientific World Journal vol 2014 Article ID 461241 6 pages2014

[22] W H Somerton Thermal Properties and Temperature-RelatedBehavior of RockFluid Systems Elsevier Science Publisher BVAmsterdam The Netherlands 1992

[23] C I Killian ldquoThe VpVs ratio after 40 years uses and abusesrdquoin Proceedings of the SEGAnnualMeeting Paper SEG 2006-1183New Orleans La USA October 2006

[24] W C James and P B Alan ldquoPetrophysics of low-permeabilitymedina sandstone Northwestern Pennsylvania AppalachianBasinrdquoThe Log Analyst vol 39 no 4 pp 36ndash46 1998

[25] Y-L Kang and P-Y Luo ldquoCurrent status and prospect of keytechniques for exploration and production of tight sandstonegas reservoirs in Chinardquo Petroleum Exploration and Develop-ment vol 34 no 2 pp 239ndash245 2007

[26] J Mahadevan M M Sharma and Y C Yortsos ldquoEvaporativecleanup of water blocks in gas wellsrdquo SPE Journal vol 12 no 2pp 209ndash216 2007

[27] R H Friedman B W Suries and D E Kleke ldquoHigh-temperature sand consolidationrdquo SPE Production Engineeringvol 3 no 2 pp 167ndash168 1988

[28] M C Ross E Rangel M L Castanier S P Hara and R AKovscek ldquoA laboratory investigation of temperature-inducedsand consolidationrdquo SPE Journal vol 11 no 2 pp 206ndash2152006

[29] K K Kelley and E G King Contributions to the Data on The-oretical Metallurgy US Bureau of Mines Bulletin WashingtonDC USA 1960

[30] J-P Zuo H-P Xie H-W Zhou and S-P Peng ldquoExperimentalresearch on thermal cracking of sandstone under differenttemperaturerdquo Chinese Journal of Geophysics (Acta GeophysicaSinica) vol 50 no 4 pp 1150ndash1155 2007

[31] Y Zhang X Zhang and Y-S Zhao ldquoProcess of sandstonethermal crackingrdquo Chinese Journal of Geophysics vol 48 no 3pp 656ndash659 2005

[32] Q-R Meng Z-Q Kang Y-S Zhao and D Yang ldquoExperimentof thermal cracking and crack initiation mechanism of oilshalerdquo Journal of China University of Petroleum (Edition ofNatural Science) vol 34 no 4 pp 89ndash98 2010

[33] F W Albaugh ldquoOil well production processrdquo US Patent2685930 1954

[34] I Barshad ldquoTemperature and heat of reaction calibration of thedifferential thermal apparatusrdquo American Mineralogist vol 37no 8 pp 667ndash694 1952

[35] D Carroll ldquoClay minerals a guide to their x-ray identificationrdquoSpecial Paper of the Geological Society of America vol 126 pp1ndash80 1970

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


with conventional stimulation methods like hydraulic frac-turing and acid treatment the advantages of formation heattreatment mainly consist in the following

(1) It prevents water blocking by evaporation of blockedwater and dehydration of clay structure [15]

(2) It enhances permeability and porosity in microscaleuniformly Meanwhile it makes anisotropy of rock inmesoscale and macroscale under control

(3) It accelerates desorption and diffusion of methane inmatrix especially for rocks rich in organic [16]

(4) Formation heat treatment does not need water sourceand it also does not contaminate groundwater It istotally eco-friendly

However systematic studies on heat treatment are stillrare and the application on stimulation of tight gas formationis urgent to understand The previous studies on formationheat treatment are based on sandstone and samplesrsquo perme-ability is relatively high [8 9 15 17] Also thermal crackingin rock which has been studied a lot in nuclear waste storagemining technique HDR geothermal extraction and stabilityanalysis of constructions is mostly based on granite thatis not the natural gas reservoir [13 18ndash21] Therefore theeffect of high temperature on tight gas reservoirs which isimportant in the development of petroleum industry needsto be evaluated Furthermore the effect of heat treatmenton different kinds of tight rocks also still needs to be distin-guished In this work samples from the representative tightgas reservoirs were treated under high temperature in argongas environment to simulate the in situ anoxic conditionSeveral lab experimental methods were comprehensivelyutilized to investigate the effect of heat treatment on physicalproperties of tight rocks Then the essence of the changesof physical properties for tight rocks after heat treatmentis analyzed comprehensively Lastly field implementation ofheat treatment process is discussed

2 Experimental Sample and Procedure

21 Samplesrsquo Description Tight rock samples in this study aretaken from three kinds of representative tight gas reservoirsShale samples are from the Longmaxi formation of LowerSilurian in Sichuan Basin which is recognized as the mostproducible and profitable shale gas reservoir in China Tightsandstone samples are from Upper Palaeozoic in Permianin Ordos Basin which is the most giant tight sandstone gasreservoir in China And the tight carbonate rock sample isfrom Feixianguan formation of Lower Triassic in northeastSichuan Basin which is the representative tight carbonategas reservoir in China Meanwhile in order to investigatethe influence of organic matter in thermal process mudstonesamples from Sichuan Basin are selected to be compared withshale samples These reservoirs are typically characterizedby various kinds of pore types complicated pore struc-ture and strong heterogeneity Porosity and permeabilitywere measured by CMS-300 Core-Automatic DeterminationInstrument for permeability more than 001 times 10minus3 120583m2 and

by LGPM700 with transient pulse decay method for perme-ability less than 001 times 10minus3 120583m2 Initial physical propertiesof these samples under conventional conditions (435 psi and20∘C) are presented in Table 1

22 Experimental Temperature Setting X-ray diffraction(XRD) analyses of these samples show that clay mineral andquartz are the main minerals (Table 2) except that tightcarbonate rock is mainly composed of dolomite The clayminerals of samplesmainly consist of illite chlorite kaoliniteand mixed-layer mineral of illitesmectite except that shaledoes not contain kaolinite Within a certain temperaturerange structure of clay minerals would be destroyed Besidesclay minerals thermal reactions can occur in other mineralconstituents such as quartz and carbonate Particularly thequartz which has a volume expansion of 27 in 2sim5 secondswhen temperature elevates to 573∘C due to the 120572 rarr 120573inversion of quartz has a dominant effect on themagnitude ofthermal expansion [19 22] Heats of reaction for several mainminerals of samples are concluded in Table 3 According tothe temperature range of heat reaction for minerals shown inTable 3 various temperature values that is 100 200 300 400500 600 700 and 800∘C were specified as the temperatureset-points to evaluate the effect of heat treatment on physicalproperties of tight rocks

23 Experimental Equipment andMethods In order to simu-late the in situ anoxic condition samples with correspondingirreducible water saturation were mounted in a tube furnacefilled with argon gas Mass of samples was measured beforeand after heat treatment by precision electronic balance ina controlled humidity oven at 20∘C and 0RH Acousticcompressional wave (P-wave) and shearwave (S-wave) transittime were measured before and after heat treatment underconventional conditions (435 psi and 20∘C) through SCMS-J Acoustics-Resistivity Measurement Equipment which isresearched and developed independently by the State KeyLaboratory of Oil and Gas Reservoir Geology and Exploita-tion of SWPU and the frequency of ultrasonic wave is170 kHz Porosity and permeability weremeasured before andafter heat treatment through CMS-300 for permeability morethan 001times10minus3 120583m2 and through LGPM700 for permeabilityless than 001 times 10minus3 120583m2 under conventional conditions(435 psi and 20∘C)

As is shown in Figure 1 the testing procedures are asfollows

(1) Measure one samplersquos mass acoustic transit timeand porosity and permeability under the conditionsshown above

(2) Mount the sample in the tube furnace Fully evacuatethe sample at 62∘C to ensure that air includingadsorbed gas is excluded from the rock Then breakvacuum with argon gas until ambient pressure ofsample returns to atmospheric pressure

(3) Heat the sample to 100∘C at a rate of 5∘Cminstarting with atmospheric temperature (20∘C) Whentemperature in tube furnace is up to 100∘C the testingtemperature would be maintained for 2 h and then




0

gLength119871

0

cmDiameter119863

0

cmPorosityΦ

0

Permeability119870

0

10minus3 um2


119901


119904

120583sm Lithology







CMS-300 LGPM700



Oscilloscope




Sample


Sample

pump

Pressuregauge

Controlvalve














119901and Δ119879








119904Δ119879119901does


119904Δ119879119901without any



094

095

096

097

098

099

100

0 200 400 600 800


MiM

0

T (∘C)


0

05

1

15

2

25Sh

ale1

Shal

e2

Shal

e3

Shal

e4

Sand

1

Sand

2

Sand

3

Sand

4

Sand

5

Carb

onat

e

Mud

1

Mud

2

Mud

3

ΔTp

ΔTs

ΔT

800∘C

ΔT

20∘C





0

05

1

15

2

25Sh

ale1

Shal

e2

Shal

e3

Shal

e4

Sand

1

Sand

2

Sand

3

Sand

4

Sand

5

Carb

onat

e

Mud

1

Mud

2

Mud

3

ΔT

sΔ

Tp



to Δ119879119901


0

10

20

30

40

50

60

70

80

90

0 100 200 300 400 500 600 700 800


T (∘C)

KiK

0




05

10

15

20

25

30

35

40

45

0 100 200 300 400 500 600 700 800


T (∘C)

ΦiΦ

0



4 Discussions

















(a) Shale


(b) Tight sandstone




(d) Mudstone





119908





Evaporation

Dehydration

Quartzphase change


Fracture network

Water phase

Mineral

Rock

Temperature

Scal

e


Decomposition


Evaporation

200∘C573∘C

Ambient temperature

100∘C

400∘C






119908and genera-




6 Conclusions




119904Δ119879119901does









Acknowledgments


References
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




0

gLength119871

0

cmDiameter119863

0

cmPorosityΦ

0

Permeability119870

0

10minus3 um2


119901


119904

120583sm Lithology







CMS-300 LGPM700



Oscilloscope




Sample


Sample

pump

Pressuregauge

Controlvalve














119901and Δ119879








119904Δ119879119901does


119904Δ119879119901without any



094

095

096

097

098

099

100

0 200 400 600 800


MiM

0

T (∘C)


0

05

1

15

2

25Sh

ale1

Shal

e2

Shal

e3

Shal

e4

Sand

1

Sand

2

Sand

3

Sand

4

Sand

5

Carb

onat

e

Mud

1

Mud

2

Mud

3

ΔTp

ΔTs

ΔT

800∘C

ΔT

20∘C





0

05

1

15

2

25Sh

ale1

Shal

e2

Shal

e3

Shal

e4

Sand

1

Sand

2

Sand

3

Sand

4

Sand

5

Carb

onat

e

Mud

1

Mud

2

Mud

3

ΔT

sΔ

Tp



to Δ119879119901


0

10

20

30

40

50

60

70

80

90

0 100 200 300 400 500 600 700 800


T (∘C)

KiK

0




05

10

15

20

25

30

35

40

45

0 100 200 300 400 500 600 700 800


T (∘C)

ΦiΦ

0



4 Discussions

















(a) Shale


(b) Tight sandstone




(d) Mudstone





119908





Evaporation

Dehydration

Quartzphase change


Fracture network

Water phase

Mineral

Rock

Temperature

Scal

e


Decomposition


Evaporation

200∘C573∘C

Ambient temperature

100∘C

400∘C






119908and genera-




6 Conclusions




119904Δ119879119901does









Acknowledgments


References
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of












119901and Δ119879








119904Δ119879119901does


119904Δ119879119901without any



094

095

096

097

098

099

100

0 200 400 600 800


MiM

0

T (∘C)


0

05

1

15

2

25Sh

ale1

Shal

e2

Shal

e3

Shal

e4

Sand

1

Sand

2

Sand

3

Sand

4

Sand

5

Carb

onat

e

Mud

1

Mud

2

Mud

3

ΔTp

ΔTs

ΔT

800∘C

ΔT

20∘C





0

05

1

15

2

25Sh

ale1

Shal

e2

Shal

e3

Shal

e4

Sand

1

Sand

2

Sand

3

Sand

4

Sand

5

Carb

onat

e

Mud

1

Mud

2

Mud

3

ΔT

sΔ

Tp



to Δ119879119901


0

10

20

30

40

50

60

70

80

90

0 100 200 300 400 500 600 700 800


T (∘C)

KiK

0




05

10

15

20

25

30

35

40

45

0 100 200 300 400 500 600 700 800


T (∘C)

ΦiΦ

0



4 Discussions

















(a) Shale


(b) Tight sandstone




(d) Mudstone





119908





Evaporation

Dehydration

Quartzphase change


Fracture network

Water phase

Mineral

Rock

Temperature

Scal

e


Decomposition


Evaporation

200∘C573∘C

Ambient temperature

100∘C

400∘C






119908and genera-




6 Conclusions




119904Δ119879119901does









Acknowledgments


References
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0

05

1

15

2

25Sh

ale1

Shal

e2

Shal

e3

Shal

e4

Sand

1

Sand

2

Sand

3

Sand

4

Sand

5

Carb

onat

e

Mud

1

Mud

2

Mud

3

ΔT

sΔ

Tp



to Δ119879119901


0

10

20

30

40

50

60

70

80

90

0 100 200 300 400 500 600 700 800


T (∘C)

KiK

0




05

10

15

20

25

30

35

40

45

0 100 200 300 400 500 600 700 800


T (∘C)

ΦiΦ

0



4 Discussions

















(a) Shale


(b) Tight sandstone




(d) Mudstone





119908





Evaporation

Dehydration

Quartzphase change


Fracture network

Water phase

Mineral

Rock

Temperature

Scal

e


Decomposition


Evaporation

200∘C573∘C

Ambient temperature

100∘C

400∘C






119908and genera-




6 Conclusions




119904Δ119879119901does









Acknowledgments


References
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of















(a) Shale


(b) Tight sandstone




(d) Mudstone





119908





Evaporation

Dehydration

Quartzphase change


Fracture network

Water phase

Mineral

Rock

Temperature

Scal

e


Decomposition


Evaporation

200∘C573∘C

Ambient temperature

100∘C

400∘C






119908and genera-




6 Conclusions




119904Δ119879119901does









Acknowledgments


References
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




119908





Evaporation

Dehydration

Quartzphase change


Fracture network

Water phase

Mineral

Rock

Temperature

Scal

e


Decomposition


Evaporation

200∘C573∘C

Ambient temperature

100∘C

400∘C






119908and genera-




6 Conclusions




119904Δ119879119901does









Acknowledgments


References
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of








Acknowledgments


References
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

research article laboratory measurement and interpretation...

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