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SPE-14371-MS中渗透储层油井压裂优化

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SPE 14371 MS 渗透 油井 优化
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SPE,SPE14371OptimizedOilwellFracturingofModerate-PermeabilityReservoirsvm.:-AmmnDrtw+mtinn&IbyIA.ImlL1,rwllwu”,,“”””..”,.---WE‘MeinbeiCopyrfght1985,.%rciityofPetrofeumEngineersThispaperwaspreparedforpresentationattheSOthAnnualTechnicalConferenceandExhibitionoftheSodetyofPetroleumEngineersheldinLeeVegas,NVSeptember&25,1985.ThispaperwasselectedforpresentationbyanSPEProgrsmCommitteefoiiowingreviewofhf~ifi~tkficon:,sinedhen....----d’=1.artm,brn!cscfbytheauthor(s).Oontenteofthepaper,esPreeermd,hsvanotbeenreviewedbytheSOCietyofPetroleumEngineersandaresubjecttocorrectionbytheauthor(a).Thematerial,aspresented,doesnotneceeeerilyreflectanypositionoftheS@efyofpetroleumEngineers,itsofioem,ormembers.pepersPmSWrtedatSPEmeetkweareSUMSCItoPubfiitiorrreviewbyEditorialCommitteeofthaSmiefyofPetrofeumEngineers.Pemtiesiontocopyisreetficmdtoanabatrectofnotmorethen200words.illustrationsmaynotbecopied.Theabstractshouldcontainconspicuousacknowledgmentofwhereandbywhomthapaperispresented.WritePublicationsManager,SPE,P.O.BoxS23S26,Richardson,TX750S3-SS36.Telex,720989SPEDAL.ABSTRACTto“conventional”fracturetreatmentsandusedtomodifyfracturetreatmentdesigns.BothsimulatedThispaperpresentsresultsfromananalysisofdataandfieldproductiondataarepresentedtoshowtheeffectoffracturingonmoderatepermeabi1ityoi1theeconomicbenefitsderivedfromthecreationofreservoirsunderprimarydepletionandsecondaryshort,highlyconductivefracturesinmoderaterecoveryprocesses.Thisanalysisindicatedthatthepermeabilityoilwells.optimumfracturehalflengthinwellshavingareser-voirpermeabilityof1-10mdisrelativelyshortandhighlyconductive.Bothsimulatedandfieldproduc-OPTIMIZATIONPROCEDUREtiondataareusedtosupportthisconclusion.TheoptimizationofoilwellfracturingrequiresthattheperformanceandcostofagivenfractureINTRODUCTIONconfigurationcanbepredicted.Reservoirandfracturedesignmodels,respectively,wereusedforHistorically,fracturestimulationshavebeenthispurpose.Resultsofthesesimulationswerethenusedtoovercomethedetrimentaleffectsofwellboredamage.These“conventional”treatmentswerecombinedinaneconomicmodeltooptimizeoilwellfracturing.generallysmallandoflimitedcapacityandlateralextent.Inrecentyears,increasedindustryactivityOilwellfracturingoptimizationrequiresthatandinterestindomesticproductionhasledtoreservoirsimulationsbeperformedtodeterminetheimprovementsinfracturingequipmentandmaterials,areservoirresponse@3agivenfractureconfiguration.greaterunderstandingoffracturemechanicsandulti-Eithersteadystateorreservoirmodelscanbeuse~rnately:tothedevelopmentofmassivehydraulictosimulatetheperformanceoffracturedwells.fracturing(MHF).ThistechnologyhasbeenusedtoHowever,reservoirmodelsw~reusedinth~sanalysiscreatelongfiniteconductivityfractures,whichaltertoallowtheeconomicbenefitsofunsteadystateflowtheflowgeometryaroundthewellboreandproviderateacceleration,andthetimevalueofmoneytobeincreasedsurfaceareatoflow,makingmany“tight”consideredintheeconomicdecision.Inaddition,US(gasreservoirscommerciallyattractive.However,inofareservoirmodelallowedtheeffectsofwell‘moderatepermeabilityoilreservoirs,thecreationofspacing,fractureconductivity,length,andorienta-shorthighlyconductivefractures,asopposedtotiontobeevaluatedaswell.Twomodelswereusedifmassivehydraulicfractures,hasbeenfoundtobethisanalysis.Athree-phase,two-dimensional,economicallyattractive.semi-implicittypemodelwasusedtopredicttheItisthepurposeofthispapertoshowaprocessperformanceofafractureinareservoirunderprimarjdepletionperformance.Arealsimulations.w~thbywhichtheoptimumfracturelengthandfracturecon-fracturesofhalflength,xf,andconductlvlty,kfw,ductivitycanbedeterminedforwellsinmoderatewereperformedinthisanalysisoftheeffectsofpermeabilityoilreservoirsunderprimarydepletionfracturingonprimarydepletionperformance.Aandsecondaryrecoveryprocesses.Theoptimumfrac-three-phasetwo-dimensional“blackoil”modelwithtureparametersdeterminedinthismannerarecomparedvariablebubblepointoptionwasusedfortheanalysi:oftheeffectsoffracturingonsecondaryrecoveryprocesses.BecausethismodelwasanexplicitReferencesand111ustratlonsatendofpaper.saturationtypemodel,theeffectivewellboreradius-–--------r.I-I-.urAmTIlTVDECCDVQ~~~2OPTIMIZEDOILWELLFRACTURINGOFMOUkKAIEF’EK17CHD1L1!J~.~.,..SPE14371conceptwasusedtocosteffectivelysimulatehydraulicfractures.Two-phaseoil/watersimulationswereperformedtoevaluatetheeffectoffractureorienta~ion,andthereforethelimitsofthisconcept.Treatmentcostestimatesweredevelopedwiththeaidofafracturedesignmodel.Fromthesesimulations,volumerequirementsforagivenfractureconfigurationwereobtained.Then,anest.iiiiat.ecftreatmentcostperfluidgallonof$1/galwasapplied.AnalysisoftreatmentsperformedinWestTexasduringthepastseveralyearsindicatesthatthisisareasonablecostestimationtechnique.Theproductionprofilesandtreatmentcostsdevelopedintheprecedingmannerweretheninputintoaneconomicmodelandtheeconomicbenefitsof~PaC~Urinnwereevaluated.....=..-Twoeconomicparameters,discountedpresentworthanddiscountedreturnoninvestment,wereusedintheeconomicanalysis.Discountedpresentworthisdefinedbythefollowingequation:PMi=FV.1/(1+i)nDiscountedreturnoninvestmentisdefined:OROIi=AFITPWofProjectofInvestment(1)(2)Botheconomicparametersrelatethetimevalueofmoneytotheeconomicdecision.However,forcapitalconstrainedprojects,presentworthwillbemaximizedwhendiscountedreturnoninvestmentisoptimized.Thisoptimizationprocedurewasusedtoevaluatetheoptimumfractureparametersforhydraulicfracturingofwellsunderprimarydepletionperformanceandsecondaryrecoveryprocesses.THEEFFECTSOFFRACTURINGONPRIMARYDEPLETIONReservoirsimulations’wereperformedtoevaluatetheeffectsofvaryingreservoirpermeability,fractureconductivityandfracturelength.Simulationresultswerethencombinedwithtreatmentcostestimatesandaneconomicanalysisoftheeffectsoffracturingonprimarydepletionperformancewasperformed.Figure1isaplotofincrementalpresentworthversusfracturehalflengthforafractureconductivityof1500md-ftandvariousreservoirpermeabilities.Thisfigurecomp~resthepresent-c-#m..-+,,waA“allWOithulaIIaGUUI=u“=,,pmhctlmstreamtoanunfracturedwellstreamandshowsthatbenefitsoffracturingdecreasewithincreasingreservoirpermeability.Thefigureshowsfora2.5mdreservoirthatthegreatesteconomicbenefitisderivedfromafracturehavinga200feethalflength.Thefigurefurthershowsforreservoirpermeabilitiesgreaterthan5mdtheoptimumfracturehalflengthis100feetorless.Fractureconductivitywasalteredandadditionalsimulationswereperformed.Theresultswerethencombinedwithtreatmentcostestimatesinordertoperformaneconomicanalysisofthebenefitsoffractureconductivity.Figure2isaplotofincrementalpresentworthversusfracturehalflengthdeveloDedfromthisanalvsisfora2.5mdreservoir.Asshownonthisplot,increasingthefractureconductivityfrom75to3000md-ftsignificantlyincreasestheeconomicbenefitoffracturing.Forexample,theincrementalpresentworthfora200feetfracturei’sincreasedfrom$11,000to$21,000byincreasingkwfrom75md-ftto3000md-ft.Further,asfractur&conductivityincreases,theoptimumfracturehalflengthincreasesaswell.Additionalsimulationswereperformedtoanalyzetheeffectsoffracturelength.Figure3showsaPIOofincrementalpresentworthversusfractureconductivityfora2.5mdreservoirandvaryingfracturelengths.Thisfigureshowsforfractureconductivitieslessthan950md-ftthereisnoeconomicbenefitassociatedwithincreasingthefracturelength.Conversely,ifthefractureconductivityisfrom1000to3000md-ft,someeconamibenefitcanbederivedfromincreasingthefractureL.ieng~nfrom100t~200feet.Itshouldbenoted,however,thatforallcasesconsideredtheoptimumfracturelengthwasnogreaterthan200feet.Thus,forwellsinmoderatepermeabilityreservoirsunderprimarydepletionperformancetheoptimumfractureisshortandhighiyconductive.THEEFFECTSOFFRACTURINGONTHESECONDARYTwo-dimensionalthree-phasesimulationswereperformedtoanalyzetheeffectoffracturingon5-spotpatternwaterfloodrecovery.Unfavorablyorientedfractureswereconsidered.Thesesimulationindicatedthatunfavorablyorientedfractures,inexcessoftwenty-fivepercent(25%)oftheinterwelldistance,weredetrimentaltorecoveryfroma5-spotwaterfloodpattern.Further,whenbothinjectionwellsandproducingwellswerefracturedthesumofthefracturehalflengthscouldnotexceedfiftypercentoftheinterwelldistancewithoutdetrimentallyaffectingrecovery.Figure4isaplotofmoveableoilrecoveryversushydrocarbonporevolumesinjectedforthecasewhereboththeproducinwellandinjectionwellina5-spotpatternarefracturedsimilarly.Thisfigureshowsthatultimaterecoveryisdetrimentallyaffectedifthefracturelengthexceedsapproximatelytwenty-fivepercent(sumofthefracturehalflengthsexceedfiftypercent)oftheinterwelldistance.Thisfiguredoesnotshow,however,thetremendousrateaccelerationbenefitsassociatedwithfracturing.SimulationswereperformedusingpropertiesfromaWestTexasreservoirtoanalyzetheeffectsoffracturingonthesecondaryrecoveryprocess.ThereservoirandsimulationparametersusedinthisanalysisaretabuiateciinTableiwiiilethefluidpropertyandrelativepermeabilitydatausedareshowinTables2and3,respectively.Analysisofthesesimulationsindicatethatinordertooptimallydepletea5-spotpattern,short,highlyconductivefrac;u~es~houldbecreatedinbothproducingwellsandiiijSCt.100+K2!!S.~~gure5isaplotofincrementalpresentworthversusfracturehalflengthforfivespotwaterfloodpatternsimulationswherethproducingwellandinjectionwellsarefracturedsimilarly.Thisfiguredisplaysthesignificanteconomicbenefitsassociatedwithincreasingfractureconductivity.Forexample,forfracturesoftwohundredfeethalflengthincreasingthefractureconductivityfrom500to5000md-ftwouldgenerateanadditional$87,000ofincrementalpresent~orth.TheSPE14371L.K.BRITT3figurefurthershowsthatasthefractureconductivityincreasestheoptimumfracturelengthincreasesaswel1.Thisfigureusespresentworthastheoptimizationparameter.Asdiscussedpreviously,foracapitalconstrainedenvironment,presentworthwillhefia~im;~ed~he~fiicc~,,”t~~r~t~rnoninvestmentis“,.,-”w,,+--optimized.Figure6isaplotofdiscountedreturnoninvestmentversusfracturehalflengthdevelopedforfractureconductivitiesof500-5,000md-ftfora5-spotpatternwhereboththeinjectionwellsandproducingwellswerefractured.Asshown,theoptimumfractureisshortandhighlyconductiveforthistypereservoir.FIELDAPPLICATIONToillustratethebenefitsofcreatingshort,highlyconductivefracturesinmoderatepermeabilityoilwells,severalfieldexampleswillbepresentedfromtheNorthCowdenandAntonIrishUnits.Figure7isamapwhichshowsthelocationoftheseunits.Thesefieldexampleswillbeusedtoillustratetheimportanceoffractureconductivitytothesuccessfulstimulationofmoderatepermeabilityoilwells.Further,theywillshowthatoptimizationoffracturelengthcanresultinreducedtreatmentvolumesandultimately,inreducedfracturingcosts.ExampleNo.i:TheNorthCowdenUnit.———@X!?9YS!!$!@!!Qw!@@!!TheNorthCowdenUnitisasecondaryrecoveryprojectwhichisoperatedbyAmocoProductionCompany.TheunitliesonthemarginoftheCentralBasinPlatformandtheMidlandBasininAndrewsandEctorCounties,Texas.Theunitcomprisesapproximatelyfifty-sevenpercent(57%]oftheNorthCowdenField,whichspansroughly200squaremiles.TheNorthCowdenFieldwasdiscoveredin1930andproducedundersolutiongasdriveuntil1950whenacooperativegasinjectionprojectwasinitiated.Theunitwasformedin1966andwaterinjectioncommencedin1967.TheNorthCowdenUnitproducesfromtheGrayburgformationwhichisofPermianAge.TheGrayburgformationishighlystratifiedandiscomprisedpredominatelyofdolomitewithvaryingpercentagesofsandandanhydrite.ThetopoftheGrayburgisatanaveragedepthof4,100feet.Theformationhasagrosspaythicknessofapproximately500feet,ofwhichapproximately200feetisproductive.TheGrayburghorizonisananticlinalstructurewiththeoilaccumulationassociatedwithacombinationstructural,stratigraphictrap.~FractureDesignandProductivityComparisonsProppedhydraulicfractureshavebeenusedformanyyearstoincreasetheproductivityorinjectivityofNorthCowdenUnitwells.These“conventional”.-----11..-<~fia~?~o?umea~~~im~tedtreat.ment.~wi2~egeikraiIyUIcapacity.Inthelastfewyears,withtheimprovementsinfracturingtechnologyandequipment,attemptshavebeenmadetogeneratehighconductivityfractures.Inthisregard,large(8/12mesh)sandwasused.Table4showsanexampleofatypicalNorthCowdenUnitfracturetreatmentdesignperformeddurinthelastfewyears.Asshown,approximately30,000gallonsofcrosslinkedfracfluid,andupto~2poundspergallonof8/12sandwereused.Pressuretransienttestingindicatedthatthefractureconductivitiesachievedwiththisdesignwereinth~rangeof1000-1500md-ft,farbelowdesignexpectations.Thesetestsfurtherindicatedthatfracturehalflengthsinexcessof300feetwerebeincreated.Thesefracturesweremuchlongerthantheoptimumfracturelengthdeterminedfromreservoirsimulations.Asaresult,thefracturestimulationdesignsweremodified.Thesemodifieddesignsusesandconcentrationsuptofivelbs/galinanattempttogeneratehigherfractureconductivity.Table5showsanexampleofamodif’ieddesign.Fracturestimulationsperformedwiththese“improveddesignshaveresultedinincreasedproduc-tivity.Table6showsacomparisonoftheperformance_=-..-TT=-.-~..~-~,.,+ththarnnue~~~~n~?~QS!9nt.OOTaWelI11-aul,ulcuWI-,!“!,=--“...wellsfracturedwiththemodifieddesign.Asshown,productionisbeingincreasedoverpreviouslevelswiththemodifiedfracturedesign.Oilproductionrates1.6timestheprefracratesarebeingreported90daysafterthestimulation.Further,themodifieddesignshaveresultedinproductivityincreaseswhichhavebeensustainedformorethan6months.RecentfracturestimulationshaveusedUDto6lbs/qalof8/12sand.Initialbeenexcellent.Asf.,-.memm+w=tinqcwillV“,,s=,,w,u“,”,.,“,..stimulations.&2!!!lX!!!Q:m@!@l!!!@@!@resultsofthesestimulationshavaresult,evenhighersandbe~~~dinfuturefractureAntonIrishUnit———FieldReview——TheAntonIrishUnitisasecondaryrecoveryprojectwhichisoperatedbyAmocoProductionCompanyTheunitislocatedinportionsofHale,Lamb,andLubbockCounties,Texas.TheAntonIrishFieldwasdiscoveredin1944andproducedundersolutiongasdriveuntil1951.Atthitime,thefieldwasunitized,AmocowasdesignatedthOperator,andpressuremaintenancebyinjectionofproducedgaswascommenced.Waterfloodoperationswereinitiatedin1969andgasinjectionceasedin1972.Presentunitdevelopmentconsistsof40acre5-spotpatterns.-r.A-*T.-:-LIl..:+....AI,--cfw~mthnInworInenncOiitr-IsIIUIIILpIUUuu==,,W,,I-,.-ClearforkformationwhichisofPermianAge.”-~~etopoftheLowerClearforkoccursataaveragedepthofccnn4-6+Th.fnvmatinnhasaarosspaythickness.l,duvIc=b.s..=,“s..s..”.”..-----~.._—ofapproximately500feet.Thenetpaysectionisapproximately250feetthickandcomposedpredominatelyofdolomiteAIUFractureDesignandProductivityComparisons—LargevolumefracturestimulationshavebeenusedintheAntonIrishUnitforseveralyears.Thetremendous6succe~softhesetreatmentshasbeendocumentedpreviously.Thesestimulationsconsistedofpumpingupto175~000gallonsoffracfluidand500,000lbsof20/40sandinconcentrationsupto12lbspergallon.Thesefracturetreatmentsweredesignedtocreatefractureswhichwererelativelyshortandhighlyconductive.However,pressuretransienttestsindicatedthatfracturesinexcessof4OPTIMIZEDOILWELLFRACTURINGOFMOOERATEPERMEABILITYRESERVOIRSSPE14371fourhundredandfifty(450)feetinlengthwerebeingSpecialrecognitionisdueR.G.Agarwal,R.O.created.ThesefractureswerenearlythreetimestheCarter,andK.G.Noltefortheirguidanceandsupporllengthoftheoptimalfractureasdeterminedfromwhileperformingthisanalysis.reservoirsimulationsinthisstudy.Asaresult,amodifiedfracturedesignwas*REFERENCESde
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本文标题:SPE-14371-MS中渗透储层油井压裂优化
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