• / 7
  • 下载费用:5 下载币  

1-s2.0-S1876380415300124-main

关 键 词:
s2 S1876380415300124 main
资源描述:
RESEARCHPAPERPETROLEUMEXPLORATIONANDDEVELOPMENTVolume42,Issue2,April2015OnlineEnglisheditionoftheChineselanguagejournalCitethisarticleas:PETROL.EXPLOR.DEVELOP.,2015,42(2):247–253.Receiveddate:15Oct.2014;Reviseddate:28Feb.2015.*Correspondingauthor.E-mail:wangyoujing@petrochina.corn.cnFoundationitem:SupportedbythePetrochinaScienceandTechnologyMajorProject(2011B-1205).Copyright©2015,ResearchInstituteofPetroleumExplorationandDevelopment,PetroChina.PublishedbyElsevierBV.Allrightsreserved.Dynamicfracturesareanemergingnewdevelopmentgeologicalattributeinwater-floodingdevelopmentofultra-lowpermeabilityreservoirsWANGYoujing1,*,SONGXinmin1,TIANChangbing1,SHIChengfang1,LIJiahong1,HUIGang1,HOUJianfeng1,GAOChunning2,WANGXiaojun2,LIUPing21.PetroChinaResearchInstituteofPetroleumExploration2.PetroChinaChangqingOilfieldCompany,Xi’an710018,ChinaAbstract:Basedonthedynamiccharacteristicsofwater-floodinginultra-lowpermeabilityoilfields,theconceptofdynamicfractureisproposedanditsformationmechanismandimpactsonoilfielddevelopmentarediscussed.Dynamicfracturesrefertothenew-generatedfracturechannelswhenbottomholepressureexceedsrockbreakdownpressureandpropagationpressure,ortheeffectivefracturechan-nelsgeneratedwhentheoriginallyclosedorfillednaturalfracturesarereactivated,duetohighpressureinnearwellboreareaofinjectionwellinalongtermwaterinjectionoftheultra-lowpermeabilityreservoir.Dynamicfractures,controlledbythecurrentstressfield,con-stantlyextendtowardthedirectionoftheoilwellwiththeriseoftheinjectedwatervolumeandbottomholepressure,untilconnectingwiththeoilwellhydraulicfractures.TheanalysisofthesealedcoringwellgroupsL76-60andL88-40locatedinthesameblockintheJAOilfield,ChangqingOilfield,NWChinashowsthatthedynamicfractureschangedtheseepagecharacteristicsofwaterdisplacingoilintheultra-lowpermeabilityreservoir,greatlyaggravatedthereservoirheterogeneity,whichledtothereductionofprofileproducingdegreeandthedistributionofremainingoilonbothsidesofthefracturesincontinuousordiscontinuousbelts.Thegenerationandpropagationofdynamicfracturesarecloselyrelatedtowaterinjectionpressure,injection-productionratio,oilandwaterwellstimulationmeasures.Whentheporosity-permeabilityconditionofthematrixallowseffectiveoildisplacement,highpressurewaterinjectionoroilandwaterwellstimulationmeasuresshouldbeavoidedasfaraspossible.Keywords:dynamicfracture;ultra-lowpermeabilityreservoir;developmentgeologicalattribute;formationmechanism;water-floodingsweptvolumeIntroductionSincethe1990s,byestablishingeffectivepressuredis-placementsystemanddevelopingkeytechnologiessuchasadvancedwaterinjection,wellpatternoptimizationandhy-draulicfracturing,lowpermeabilityoilfieldshavebeende-velopedeffectively[1−3],withthelowerlimitofpermeabilitygoingdownandcrudeoiloutputgoingupconstantly.Atpre-sent,thereservoirswithpermeabilityaslowas0.3×10−3μm2haverealizedwaterinjectiondevelopment.Havingenteredintomiddle-highwatercutstage,typicalultra-lowpermeabil-ityoilfieldsrepresentedbytheAnsaiandJinganoilfieldsinOrdosBasinandtheXinminandXinlioilfieldinSongliaoBasintookonrapidincreaseofwatercut,largedropofoilrecoveryrate,andbigchallengeinkeepingproductionstable.Uncertaincontrollingfactorsanddistributionpatternofre-mainingoilbecomethebottleneckrestrictingoilrecoveryenhancementoftheseoilfields.Basedonthewaterinjectiondynamiccharacteristics,thisarticlepresentsthatdynamicfracturesareanewdevelopmentgeologicattributeoccurringinthemiddle-highwatercutstageofthiskindofultra-lowpermeabilityreservoir,andanimportantfactorcontrollingremainingoildistribution,andwealsodiscussitsformationmechanismandimpactonoilfielddevelopment.1.ConceptofdynamicfractureWiththedeepeningofoilfielddevelopment,thetypicalul-tra-lowpermeabilityoilfieldssuchasAnsaiandXinminshowthemaincontradictionofdirectionalwaterbreakthroughofproducersafterenteringintomiddle-highwatercutstage.StatisticsontheWYblockoftheAnsaioilfieldshowthat89%oftheproducersshutdownduetohighwatercutorconvertedtowaterinjectorsarelocatedinthedirectionconnectingwithinjectorsintheoriginalwellpattern,thatisthemaximumWANGYoujingetal./PetroleumExplorationandDevelopment,2015,42(2):247–253−248−Fig.1.Performancecharacteristicsofdynamicfractures.horizontalprincipalstressdirectionofcurrenttectonicstressfield(inshortastheprimarydirectionwell).Theirwatercutrisesinstepmanner(Fig.1a),welltestinginterpretationcurvesofcorrespondinginjectorsshowfractureseepagecharacteristics(Fig.1b),theprofilesofwaterabsorptionshowpeakwaterabsorptionofindividuallayers(Fig.1c),tracermonitoringshowsobviousdirectivity(Fig.1d).ThepermeabilityofTriassicYanchangreservoirinOrdosBasinisgenerallylessthan10.00×10−3μm2.ThecorrelationbetweenporosityandpermeabilityofthemajorpayChang61inAnsaioilfieldispoor(Fig.2).Theaveragematrixperme-abilityfromcoreanalysisis1.29×10−3μm2,butatpresent,theeffectivepermeabilitythroughwelltestinginterpretationis1-2ordershigherthanthatofcoreanalysis.StatisticalanalysisonthepermeabilityfromwelltestinginterpretationshowsthattheWYblockhasanaveragepermeabilityof10.54×10−3μm2,itsratiowiththematrixpermeabilitycanreachmorethan5-8.Thefracturehalflengthobtainedfromwelltestinginterpreta-tionismorethan200m,andfracturehalflengthhasagoodcorrelationwithpermeability(Fig.3).Thesewaterfloodingdynamicresponsesshowthatduringthelongtermwaterinjectiondevelopmentofultra-lowper-meabilityreservoirs,duetopressurebuildupnearwaterin-Fig.2.Correlationchartofporosityandpermeability.Fig.3.Correlationchartoffracturehalflengthandpermeability.WANGYoujingetal./PetroleumExplorationandDevelopment,2015,42(2):247–253−249−jectors,whenbottomholepressureexceedsrockfractureandpropagationpressure,fracturesinitiate,ortheclosednaturalfracturesinoriginalstateareresurrectedintonew,effectivefracturechannels.Thesefracturesarecontrolledbycurrenttectonicstressfield.Withtheincreaseoftheinjectedwatervolumeandbottomholepressure,thesefracturesconstantlyextendtowardthedirectionoftheproducer,untilconnectingwithhydraulicfractures.Theauthorsnamethesenew,effec-tivefracturesasdynamicfractures,whichhavesimilarforma-tionmechanismwithwaterinjectiongrowingfracturesmen-tionedinliteraturesabroad[4−5].2.Formationmechanismofdynamicfractures2.1.NewlygeneratedfracturesThepressurechangepatternintheprocessoffracturegen-erationisthat,firstthebottomholepressurekeepsrisingtotherockcrackingpressureandthefractureinitiates[6];thenthepressuredecreasesslightly.Underthefracturepropagationpressure,thefracturesgrowandextendconstantly.Therockfracturingpressureiscalculatedbythefollowingequation[7]:()fprtpo21υpppkpSυ⎛⎞=+−−+⎜⎟−⎝⎠(1)where,pfisthefracturingpressure,MPa;ppistheporepres-sure,MPa;poistheoverburdenrockpressure,MPa;υisPoisson’sratio;kisthegeologicaltectonicstresscoefficient,dimensionless;Srtistherocktensilestrength,MPa.Thefracturepropagationpressurecanbecalculatedas[5]:()tipHmin2fπ21UEpσυr=+−(2)where,ptipisthefracturepropagationpressure,MPa;σHministheminimumhorizontalprincipalstress,MPa;Uistheseamsurfaceenergy,J/cm2;Eiselasticitymodulus,MPa;rfisthefracturehalflength,cm.Thefracturepropagationpressurecanbesimplifiedas[6]:tipHminrtpσS≈+(3)thatis,fracturepropagationatleastneedstogetoverthesumoftheminimumhorizontalprincipalstressandrocktensilestrength.Thefracturesinitiatewhenbottomholepressureexceedsrockfracturingpressureduetopressurebuildupnearinjectorintheprocessofwaterinjection,andpropagatetowardtheproducerwiththeriseofinjectedwatervolumeandbottomholepressure,untilconnectingwithhydraulicfracturesoftheproducer.Producersofultra-lowpermeabilityreservoirsaregenerallyputintoproductionafterhydraulicfracturing,anddeflagration,explosionfracturingandcompositeperforationareusuallyappliedtotheinjectorinordertostrengthenwaterinjectioncapacity.Thedeflagrationandexplosionfracturingstimulatetheformationnearthewell,resultingintheforma-tionofdozensofshortradialincidentfractures[8−9],whicharenotcontrolledbystressandmuchsmallerthanartificialhy-draulicfracturesinscale.Compositeperforationtechnologyallowsperforationandhighenergygasfracturingsimultane-ously,notonlyimprovingthereservoirporosityandperme-abilitybutalsomakingtheperforationtunnelintheformofcrackextendforward,andformmulti-directionfractures[10−11].Thenewsmallscalefracturescreatedbydeflagration,explo-sionfracturingandcompositeperforationpropagatetowardsthecurrentmaximumhorizontalstressunderfractureexten-sionpressure,whichcouldcausesuddenwater-outofproduc-erslocatedintheprimarydirection.Accordingtorockmechanicsexperimentandanalysisofdipoleacousticlog,Chang6intervalofTriassicYanchangFormationinWYblockhasaPoisson’sratioof0.122−0.335,elasticitymodulusof7.30−13.66GPa,tensilefracturingpressureof23.6−28.8MPa,minimumhorizontalprincipalstressof17−20MPa,androcktensilestrengthof3.5−5.0MPa,sothecalculatedfracturepropagationpressureisroughly20.5−25.0MPa.Thebottomholepressureofsomeinjectorshavereachedthefracturepropagationpressure.Un-derthecurrentwaterinjectiondevelopmentregime,newfracturesextendcontinuouslyandfinallyconnectwithhy-draulicfracturesoftheproducers,formingfractureseepagechannels.2.2.NaturalfracturesGenerallylowpermeabilityreservoirshavenaturalstruc-turalfractures[12−13].Becauseoftheeffectofpaleo-tectonicstressfieldintheYanshanianandHimalayanperiods,twosetsofnaturalfracturesoccurintheTriassicYanchangFormationinOrdosBasin.IntheYanshanianperiod,asetofconjugateshearfracturesofNWandEWdirectiongeneratedduetotheNWW-SEEhorizontalcompressiontectonicstress,andintheHimalayanperiod,asetofconjugateshearfracturesoftheSNandNEdirectionformedbecauseofNNE-SSWhorizontaltectoniccompression[14−17](Fig.4).InAnsai-ZhijingareaofOrdosBasin,themaximumhorizontalstressdirectionofthepresenttectonicstressfieldisaboutNE70°,thefracturesparalleltothisdirectionaremorelikelytobeopened,revived,andintensified.WhereasNWfracturesformedinYanshanianandSNfracturesformedintheHimalayanarerestrainedun-derthepresenttectonicstressfield.Themainfracturedirec-Fig.4.Rosediagramofnaturalfractureoccurrence(modifiedondataprovidedbyChangqingOilfield).WANGYoujingetal./PetroleumExplorationandDevelopment,2015,42(2):247–253−250−tionongeologicaloutcropsareNE92°andNE22°(Fig.5).Highanglefracturescanalsobeobservedoncoresampleswithadipangleofabout80°(Fig.6)andthefracturelengthof40−70cm,andsomesmallcalcitecementationmassonthefracturesurface.Analysisofimagelogdatashowsthefracturedipanglerangesfrom71°to85°andfracturestrikeismainlyNEE(Fig.7).Duetopressurebuildupinnearwellboreareaofinjectorsintheprocessofwaterfloodingdevelopment,whenthebottomholepressureexceedsthefracturepropagationpressure,thenaturalfracturesareactivatedfrominvalidfrac-turestoeffectiveonesandextendcontinuously,formingdy-namicfractures.3.Impactofdynamicfracturesonthedevelopmentofultra-lowpermeabilityoilfieldsTheformationofdynamicfracturesaggravatesthehetero-geneityofultra-lowpermeabilityreservoirsinmiddle-highwatercutstage.Thebigpermeabilitydifferencebetweenfracturesystemandmatrixwouldaffectthesweptvolumeofwaterflooding.TakingseveraltypicaldevelopmentblocksofChang6oillayerofYanchangFormationinOrdosBasininmiddle-highwatercutstagewithrichsealedcoringdataasexamples,thisarticlediscussestheimpactofdynamicfrac-turesondevelopmentofultra-lowpermeabilityoilfields.3.1.ImpactonprofileproducingdegreeTheW16-15sealedcoringwellgroup,locatedinthecenterofWYBlockofASoilfield,isdevelopedbyirregularsquareinvertednine-spotwellpattern.WhendrillingthesealFig.5.Fracture(geologicoutcrop).Fig.6.Fracture(core).Fig.7.WJ16-155imaginglog.coredwell,thiswellgrouphadanaveragesinglewellproduc-tivityof0.49t/d,totalwatercutof85.5%,andrecoveryper-centofreservesof16%.PutintoproductiononAugust,1990,theprimarydirectionwellW15-18sawinjectedwaterafterthreeyearsofproduction,andthenthewatercutroseinstepmanner(Fig.1a).Whendrillingthesealcoredwell,thepro-ducerW15-18hadawatercutof76.2%,productivityof0.32t/d,andcumulativeoilproductionof0.9106×104t.AnalysisshowsthatthewaterinproducerW15-18isfrominjectorW16-15,thegenerationofdynamicfracturesledtothehighwatercutofW15-18.Inordertofindoutthewater-outstatus,eightsealedcoringwellsweredeployed,atdifferentwellspacingandrowspacinginthewellgroup(Fig.8).Throughcarefulobservationanddescriptionofcoreinter-valsofthese8sealedcoringwells,incombinationwithdrip-pingwaterexperiment,coresettlementexperiment,fluores-centdisplayandcalculationofcoredisplacementdegree,thewaterflushingstatuswasanalyzed(Table1).Theresultshows,WANGYoujingetal./PetroleumExplorationandDevelopment,2015,42(2):247–253−251−Fig.8.WelllocationanddevelopmentstatusofW16-15sealedcoringwellgroup.Theradiussizeoftheproducersymbolreflectsthevolumeofdailyfluidproduction,redrepresentsoil,andbluerepresentswater.whenwatercutofW16-15sealedcoringwellgroupwas85.5%,thewaterfloodingproducingdegreeofthe8wellswas50.6%,andthestrongwaterfloodedpercentwasmerely13%.Thegenerationofdynamicfracturesreducestheprofileproducingdegreeunderthepresentwellpattern.3.2.ImpactonremainingoildistributioninplanLocatedinthesameblockofJAoilfield,sealcoredwellgroupL76-60andL88-40startedtoproducein2000withsquareinvertednine-spotwellpattern.Whendrillingsealedcoringwells,wellgroupL76-60hadanaveragesinglewellproductivityof3.95t/d,totalwatercutof47.2%andrecoverypercentofreservesof9.95%.Twosealedcoringwellsweredeployedinthisgroup(Fig.9a).Whendrillingsealedcoringwell,wellgroupL88-40hadanaveragesinglewellproduc-tivityof7t/d,totalwatercutof2.5%andrecoverypercentofreservesof21.4%,onlyonesealedcoringwellwasdeployedinthisgroup(Fig9b).Affectedbydynamicfrac-Table1.StatisticsonwaterfloodinglevelofW16-15sealedcoringwellgroup.WellVerticaldistancetofracture/mDistancefromin-jector/mOillayerthick-ness/mWaterfloodedsectionthick-ness/mPercentageofwaterfloodedthickness/%Percentageofweakwaterfloodedthickness/%Percentageofmod-eratewaterfloodedthickness/%Percentageofstrongwaterfloodedthickness/%WJ16-155011724.1423.0896.0482726WJ16-151018722.0610.6548.0433423WJ16-158021326.1016.4463.0562915WJ16-156427424.5516.0065.086113WJ16-1526813120.088.8744.0572616WJ16-15910115627.3411.0540.071300WJ16-15311811313.083.9630.010000WJ16-15413820023.724.4719.010000Average22.6311.8250.6632413Notes:Averagewaterfloodedpercentageateverylevelistheratioofthesumof8wellswaterfloodedthicknessateveryleveltothetotalthick-nessofthe8wells.Fig.9.Horizontaldistributionpatternofwatercut.Theradiussizeoftheproducersymbolreflectsthevolumeofdailyfluidproduction,redrepresentsoil,andbluerepresentswater.WANGYoujingetal./PetroleumExplorationandDevelopment,2015,42(2):247–253−252−tures,theproducersinwellgroupL76-60showwaterbreak-throughorsuddenwaterfloodingalongthedirectionoffrac-turehorizontally,whilethedisplacementdegreeinlateralisweak.Theremainingoilismainlydistributedonbothsidesofthedynamicfracturesincontinuousordiscontinuousbelts.Incontrast,inwellgroupL76-60,waterdistributionispatchyandcentersaroundinjectors.Thewaterfloodingfrontalmovementisrelativelyevenandtheremainingoildistributioniscontinuous.4.DiscussionsDynamicfractureshaveobviousfeaturesondevelopmentperformance,buttheyaredifficulttobecharacterizedandcomplicatedinformationmechanism.Theinitiation,activa-tionandpropagationofdynamicfracturesarecloselyrelatedtowaterinjectionpressure,injection-productionratio,pro-duceran
展开阅读全文
  石油文库所有资源均是用户自行上传分享,仅供网友学习交流,未经上传用户书面授权,请勿作他用。
0条评论

还可以输入200字符

暂无评论,赶快抢占沙发吧。

关于本文
本文标题:1-s2.0-S1876380415300124-main
链接地址:http://www.oilwenku.com/p-70326.html

当前资源信息

吾王的呆毛

编号: 20180607204856407371

类型: 共享资源

格式: PDF

大小: 3.54MB

上传时间: 2018-06-08

广告招租-6
关于我们 - 网站声明 - 网站地图 - 资源地图 - 友情链接 - 网站客服客服 - 联系我们
copyright@ 2016-2020 石油文库网站版权所有
经营许可证编号:川B2-20120048,ICP备案号:蜀ICP备11026253号-10号
收起
展开