页岩油开采外文文献翻译.docx

页岩油开采外文文献翻译.docx

《页岩油开采外文文献翻译.docx》由会员分享，可在线阅读，更多相关《页岩油开采外文文献翻译.docx（13页珍藏版）》请在冰豆网上搜索。

页岩油开采外文文献翻译

页岩油开采外文翻译中英文2019

英文

Improvingoilrecoveryfromshaleoilreservoirsusingcycliccoldcarbondioxideinjection–Anexperimentalstudy

KhalidElwegaa，HosseinEmadi,etc

Abstract

Inthisstudy,effectsofinjectinggastemperatureandpressureonoilrecoveryfactor（RF）ofshaleoilreservoirswereinvestigatedbyimplementingcycliccoldcarbondioxide（CO2）injectiononEagleFordShaleOilcoresamples.Also,effectsofinjectinggastemperatureonporosity,permeability,andbrittlenessindicesofthesecoresampleswereassessed.

AnexperimentalsetupwasdesignedandbuilttoimplementCO2 cyclicgasinjectionandthermalshocktests.FourEagleFordShaleoutcropcoresampleswereusedinthisstudy.Thesaturatedsampleswereheatedto180°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. [9] 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