页岩油开采外文文献翻译Word下载.docx

页岩油开采外文文献翻译Word下载.docx

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Fandcarbondioxideatvariouscombinationsofpressure（1000psi,2000psi,3000psi,and4000psi）andtemperature（−15°

F,0°

F,32°

F,and74°

F）wasinjectedintothem.OilRFforeachexperimentwasmeasuredafterfivedaysofproductionperiod.Additionally,porosity,permeabilityandultrasonicvelocityofeachcoresampleweremeasuredbothpriortoandafterconductingtheexperiment.

TheresultsindicatethatinjectingCO2 

atlowtemperatureresultsinhigheroilrecoveryfactor（upto7%）thaninjectingcarbondioxideatambienttemperature.ItwasalsoobservedthatinjectingcoldCO2 

enhancedbothporositiesandpermeabilitiesofthecoresamples.Theporositiesandthepermeabilitiesofthecoresamplesenhancedbyupto3.5%and8.8%,respectively.Also,anoticeablereduction（between100 ft/sand400 ft/s）inP-wavevelocitywasobservedafterinjectingthecoldgasintothecoresamples,whichisanindicationofcreatinginducedfractures.Theresultsalsorevealedthatinjectingthecoldgasincreasedthebrittlenessindicesofthecoresamplesbyupto8.Hence,cycliccoldcarbondioxideinjectioncouldbepotentiallyimplementedintheshaleoilfieldstoimprovetheefficiencyofthecurrentindustrypracticeofcyclicgasinjectiontechnique.

Keywords:

Shaleoilreservoirs,Cyclicgasinjection,Carbondioxide,Oilrecovery,Thermalshock

1. 

Introduction

Shaleformationshaveultra-lowpermeabilitiesanddonotproduceeconomicallyunlessfracturingtreatmentsareperformed.Despiteusingcurrentstimulationtechniques,shalereservoirsonlyproduce5–7%oftheirinitialoilinplace.Therefore,researchersarestillworkingonexploringnewtechniquestoimproverecoveryfactor（RF）inshale-oilreservoirs.Consequently,severalEnhancedOilRecovery（EOR）techniqueshavebeenstudiedtoimproveultimateoilRF.Oneofthemostpromisingtechniquesiscyclicgasinjection“HuffandPuff”,whichhasbeensuccessfullyimplementedinbothconventionalandunconventionalreservoirsusingdifferentgases（nitrogenandcarbondioxide）.

Inthisstudy,effectsoftemperatureofinjectingCO2 

onoilRFinshaleoilformationswasinvestigated.Inthisexperimentalstudy,CO2 

wasinjectedintofourcoresamplesatdifferentpressuresandtemperaturesandoilRFattheendofeachtestwascalculated.

Itisbelievedthatrapidlyinjectingcoldgasintohotformationscreatescracksattheexposedsurfaceareaoftherock,whichincreasesoilRF.Thistechniqueiscalledthermalshocking.Sincethermalshockcreatesfracturesattherocksurface,itisbelievedthatporosity,permeabilityandrockmechanicalpropertiesoftherocksampleswillbealteredtoo.So,porosityandpermeabilityofthesamplesweremeasuredbeforeandaftereachinjectiontest.Also,ultrasonicvelocitymeasurementtestswereconductedtoassesschangesindynamicyoung’sModuliandPoisson’sratiosofthecoresamples.

SinceEagleFordisoneofthelargestunconventionalresourcesintheU.S.,coreplugsfromitsoutcropwereobtainedandusedinthisstudy.Additionally,CO2 

wasusedinthisexperimentalstudybecauseofitssuccessfulimplementationsinEORoperationsinthepastdecades. 

[13] 

reportedthatthefollowingparametersmaycontributetoincreaseinoilRFusingcarbondioxide;

reductionofoilviscosity,miscibilityeffects,andinternalsolutiongasdrive.

1.1. 

Cyclicgasinjectionmethod

CyclicGasInjectionalsoknownashuff-and-pufftechniqueisanefficientEORmethodinwhichagasisinjectedintoareservoireitherinmiscibleorimmisciblecondition（huffcycle）.Thenthewellisshut-infora“soak”periodtoallowtheinjectedgastointeractwiththeformationoilandreachequilibrium.Attheendofthesoakingperiod,theproductionisresumedthroughthesamewell（puffcycle）.

Thismethodhasbeensuccessfullyimplementedinshaleoilfields. 

[9] 

reportedthatCO2 

greatlyenhancesthediffusionprocess,whichimproveshydrocarbontransportintightmatrixes（especiallydenselyfracturedshale-oilformations）.

UsingCO2 

andshalecoresfromMancosandEagleFord, 

[4] 

conductedalaboratorystudytoinvestigateeffectsofsoakingperiod,soakingpressureandnumberofcyclesonoilRF.TheresultsshowedthatcyclicCO2 

injectionisaneffectivemethodtoimproveoilRFfromshaleoilreservoirs. 

conductedanexperimentalworkinjectinghigh-pressureCO2 

into21coresamplesfromBakkenshaleformationtoenhancethediffusion-dominatedflowinthereservoirmatrix.TheresultsindicatedthatCO2 

isabletorecoverupto99%ofoilfrommiddleBakkenformationand68%fromupperandlowerBakkenformations.AnotherCO2 

huff-n-puffexperimentalstudyinasupercriticalstatewascarriedoutusinglowpermeabilitycoresamples.TheresultsshowedthatthecyclicCO2 

injectioninsupercriticalstatecansignificantlyimprovetheefficiencyofoilfielddevelopmentforlowpermeabilityreservoirs 

[15].Incontrast,formationdamagecouldoccurwhenCO2 

isinjectedintoformationsduetocalciumcarbonateprecipitationandbrinecontent.SeveralparametersaffecttheinteractionbetweenCO2 

andformationrockincludingpressure,temperature,brinecompositionandCO2 

injectionrate.ThereactionbetweenCO2 

andformationrockcouldresultinpermeabilityreduction 

[11].

Inadditiontotheexperimentalstudies,CO2 

cyclicgasinjectiontechniquewassuccessfullyimplementedinsomeoilfields.Thismethodwassuccessfullyimplementedon240wellsintheBigSinkingFieldofeasternKentucky,USA.UsingliquidCO2 

resultedinadditionalrecoveryof180,000barrelsofoilfromthefield 

[10].AnotherfieldimplementationofCO2 

cyclicgasinjectionwascarriedoutinJiangsuoilfield,China.TheresultsdemonstratedimprovementinwellproductivityduetodissolutionofCO2 

andnearwellboredamageremoval 

[20].

1.2. 

Lowtemperaturegasinjection

Inthistechnique,gasatalowtemperatureisinjectedintohotreservoirs.Thisprocessiscalledthermalshocktechnique,whichleadstocreatingthermalstressontherock.Thethermalstressresultsincreatingnewfracturesand/orextendingexistingcracksyieldingtohigheroilRF.UsingEq.

（1）,thermalstressappliedtoasolidbodyduetotemperaturechangeiscalculated.

Inthelastfewyears,experimentalworkshavebeenconductedtostudythermalshocktechniqueanditsapplicationsintheoilandgasindustry.Usingliquidnitrogen, 

[2] 

conductedcryogenicfracturingtestsonconcrete,tightsandstone,andNiobrarashalesamples.Theresultsshowedthatinjectingliquidnitrogennotonlyenhancesrocks’permeabilities（especiallyshalesamples）,butalso,hasalmostnoformationdamagepotential. 

[23] 

conductedrockmechanicalpropertiestestsundercryogenicconditions（rocksamplesweresubjectedtoliquidnitrogen）.Theresultsshowedthatshearandtensilestrengthsoftherocksamplessignificantlydecreasedafterbeingsubjectedtoliquidnitrogen.Thermalshockcausedbythecryogenictreatmentcouldcreatenewmicrofracturesandextendtheexistingones. 

[21]conductedcryogenicfracturingexperimentstoinvestigateitseffectsonthepermeabilitiesofeight-inchcubicsyntheticrocksamples（concrete）.Eighttinythermocoupleswereembeddedinthesamplestomonitorchangesintemperatureduringthetest.Liquidnitrogenwascirculatedintothesamplesthrough6-in.-deepholeswhilethesamplesweresubjectedtotriaxialcompression.Theresultsshowedthatthepermeabilitiesoftheaffectedareaincreased. 

[3] 

concludedthatcryogenicfracturingisastimulationtechnology,whichdeployscryogenicfluidstofractureunconventionaloilandgasreservoirs.

[6] 

conductedanon-isothermalcompositionalsimulationstudytoexamineeffectofinjectinglowtemperatureCO2 

onoilRFinahightemperaturereservoir.TheresultsshowedthatinjectingliquidCO2 

increasesultimateoilRFby8.73%comparedtosupercriticalCO2 

injectioninisothermalmode（200°

F）after24 yearsofproduction.

2. 

Experimentalwork

Inthisstudy,severalexperimentswereconductedtoinvestigateeffectoftemperatureofinjectingCO2 

onoilRFinshaleoilreservoirs.Detaileddescriptionofporosity,permeability,ultrasonicvelocitymeasurementsandcyclicgasinjectionexperimentaregiveninthefollowingsections.FourEagleFordcoreplugswereusedinthisexperimentalstudy.Thesecoreswerecutparalleltothebeddingplanesandwereall1.5″indiameterand3″inlength.

2.1. 

Porositymeasurement

Aheliumporosimeterwasusedtomeasuretheeffectiveporositiesofthecoresamples.Theporositiesweremeasuredbothpriortoandafterconductingtheinjectiontests.

2.2. 

Permeabilitymeasurement

NewResearchEngland（NER）AutoLab1500（wasusedtomeasurepermeabilitiesusingcomplextransientmethodandhelium. 

Fig. 

showsajacketedcoresamplemountedbetweenthelow-permeabilitytransducerandthebottomplug.ThepermeabilitiesofallcoresamplesweremeasuredbeforeandafterconductingCO2 

injectiontests.Theresultswerethenusedtostudyeffectofthethe