阻垢缓蚀剂对含沥青质油井产能的影响.docx
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阻垢缓蚀剂对含沥青质油井产能的影响.docx
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阻垢缓蚀剂对含沥青质油井产能的影响
Effectofscaleandcorrosioninhibitorsonwellproductivityinreservoirscontainingasphaltenes
Abstract
DuringoilproductionfromseveralwellsinArabianGulfarea,significantproductivitydeclinewasnoticed.Oneofthereasonsbehindtheproductivitydeclinemightbeasphalteneprecipitation.Productiondataoftheparticularwellswerecollectedandanalyzed.Itwasfoundthatmanyofthesewellswereinjectedwithscaleandcorrosioninhibitorsindownholeandsurfaceequipment.Thus,itwasdesiredtoinvestigatethepotentialofformationdamageduetoasphalteneinthepresenceofscaleandcorrosioninhibitorsasfieldchemicals.Theeffectofasphaltenesonthewettability,surface,andinterfacialtensionsweremeasuredinthepresenceofscaleandcorrosioninhibitors.Itwasobservedthatthescaleinhibitordidnotindicateanyalterationofthewettability,whilethepresenceofcorrosioninhibitorindicateshighpotentialforwettabilitychangeintooil-wetconditionsespeciallyinthepresenceofasphaltenicoil.Similarresultswereobtainedfromthemeasurementsofsurfaceandinterfacialtensions,inwhichcorrosioninhibitorsshowedasignificantdecreaseinsurfaceandinterfacialtensions.Toassessthepotentialofasphalteneprecipitationinthepresenceofbothinhibitorsandtostudytheeffectofasphaltenesontheoilproductivity,floodingexperimentswerecarriedoutandoil/waterrelativepermeabilitywasdetermined.
Theresultsoffloodingdisplacementsshowedthatthepresenceofscaleinhibitorsindicatesnoeffectontheoil/waterrelativepermeabilityeveninthepresenceofasphaltenes,whileasignificantdecreaseinoilrelativepermeabilityassociatedwithanincreaseofresidualoilsaturationwasobservedinthepresenceofcorrosioninhibitors.
Mixtureofscaleandcorrosioninhibitorsshowednoeffectonrelativepermeabilitycurves.
1.Introduction
Asphaltenesaregenerallydefinedassolidmaterials,whichareinsolubleinn-pentaneorn-heptaneandremainsolubleinbenzene,andtheyexistintheoilasacolloidalsuspension,stabilizedbyresinadsorbedontheirsurface(Gholoumetal.,2003;Al-Sahhafetal.,2001;Yinetal.,2000;Edler,1999;KokalandSayegh,1995).Asphaltenesprecipitationanddepositionoccurinthefacilitiesatthesurface,inthewelltubing,ornearwellboreduetodifferentreasonssuchascompositionalchangesandpressurevariations.Thesephenomenacreateaserioustechnicalandeconomicalproblemduringproductionandtransportationofcrudeoilandwillreducethewellproductivityorinjectivity(Kocabas,2003;Sarma,2003;ZekriandEl-Mehaideb,2003;Kokaletal.,2002;Shedid,2001).Asphaltenedepositionmayoccuralsoinfieldsinwhichchemicaltreatmentsuchasenhancedoilrecoverymethodsoracidizingprocesswasconducted(ZekriandEl-Mehaideb,2003;Sarma,2003;Yangmingetal.,2003;Yinetal.,2000).
However,thetreatmentorremovalofasphalteneprecipitationespeciallynearwellboreorinthewelltubingrequiresworkoveroperations,inwhichdifferentmethods,suchaschemical,thermal,ormechanicalmethod,canbeapplied.Theseoperationsareexpensiveandtime-consuming.Therefore,preventingasphaltenedepositionisessentialtomaintainwellproductivity.Thiswasthetopicofmanyinvestigations,buttheeffectoffieldchemicals,suchasscaleandcorrosioninhibitorsonasphalteneprecipitation,wasnotstudied.
Inthispaper,laboratoryinvestigationswerecarriedoutusingcrudeoilwithandwithoutasphaltenestoevaluatethecompatibilityofscaleandcorrosioninhibitorswithasphaltenicoilandtostudytheflow
behaviorofasphaltenicoilbasedonoil/waterrelativepermeabilityapproach.
2.Materialsandexperimentalprocedures
Tostudytheeffectofscaleandcorrosioninhibitorsonformationdamageinthepresenceofasphaltenicoil,pre-investigationsonrelevantphysicalpropertieswerecarriedout,suchascontact
angle,andsurfaceandinterfacialtensions.Finally,differentfloodingexperimentswereperformedtoevaluatethepresenceofasphaltenesaswellastheeffectofscaleandcorrosioninhibitorsonoil
productivity.
2.1.Crudeoil
Arabianlightcrudeoilwastaken,whichhasaviscosityof11cPandAPIgravityof31.28
measuredatambientconditions.Theasphaltenicoilwaspreparedbymixingacertainweightofsolidasphalteneparticlesinthecrudeoilusingmagneticstirringat200rpmforaperiodof8h.Theasphalteneconcentrationsselectedinthisstudywerebasedonthesolubilitybehaviorofasphaltenesintheusedcrudeoil.Themaximumconcentrationwasdeterminedbyobservingflocculationandprecipitationofasphaltenesforaperiodof5daysafterpreparingthesamples.Itwasfoundthattheusedcrudeoilcouldstabilizeanasphalteneconcentrationupto3%duetothehighpercentageofresinexistinginthecrudeoil,whichisabout15%(KokalandAl-Juraid,1998).Thecontactangle,andsurfaceandinterfacialtensionsoftheobtainedasphaltenicoilsamplesweremeasuredinthepresenceofbrineaswellasbrinecontainingscaleandcorrosioninhibitors.Thecontactangleformedbetweentwoimmisciblefluidsisimportanttoevaluatethepreferentialwettingcharacteristicsofthesolidsystem.Wettabilitydescribesthetendencyofonefluidtospreadonoradheretoarocksurfaceinthepresenceofanotherimmisciblefluid(Anderson,1986;Marcella-DeSilvaandDawe,2003).Thesurfaceandinterfacialtensionsdescribetheinteractionsbetweenmoleculesofdifferenttypeandtheinterfacialtensionarisesduetotheattractiveforcesbetweenthemoleculesinthedifferentfluids.
TheasphaltenesamplesassolidparticlesshowedinFig.1wereobtainedfromtheKuwaitInstituteforScientificResearch(KISR)andtheseparationprocessisdescribedinthepaper(Gholoumetal.,2003).
Fig.1.Photographofasphaltenesample.
2.2.Scaleandcorrosioninhibitors
Fivedifferentscaleinhibitors(S-10,S-27,S-45,S-78,andS-81)andtwodifferentcorrosioninhibitors(C-68andC-62E),whicharewidelyusedinthepetroleumindustry,wereappliedthroughthisstudy.1Theconcentrationoftheinhibitorsolutionswassetat200ppmaspermanufacturerrecommendation.Thesurfacetensionofallinhibitorsolutionsaswellastheinterfacialtensionbetweeninhibitorsandcrudeoilwithandwithoutasphaltenesindifferentconcentrationsweremeasuredusingaringtensiometer.
2.3.Coresamples
Bereasandstonecoresamplesconsistingmainlyofquartzwereusedtoconductthefloodingexperiments.Thecoresampleswerewashedanddriedinanovenat1208Cfor24h.Thedimensionsofthecoreplugsrangebetween9.8and10.3cminlengthand5.2cmindiameter.ThecoresamplewasplacedinHockcell(coreholder)witharubbersleevearoundit.Aconfiningpressurewasappliedusinghandpump.Thecoresamplewasevacuatedandsaturatedwith5%brine.Theporevolumewasmeasuredandtheporositywascalculated.ThecorepermeabilitywasthendeterminedusingDarcy’sequationatconstantflowratebyrecordingthepressuredropbetweentheinletandoutletsides.Theobtainedporositiesandabsolutepermeabilitiesvariedbetween24%and25.1%,andbetween500and610mD,respectively.Thecoresampleswerethenfloodedwiththecrudeoilanddisplacedwithbrineatconstantflowratewithcontinuousrecordingofthepressuredroptodeterminetherelativepermeability.However,fourdifferentseriesofdynamicdisplacementtestswerecarriedoutwithfollowingprocedures:
Firstseriesincludescorefloodingusingcrudeoildisplacedby5%brinerepresentedasreferenceexperiment.
Secondseriesincludescorefloodingusingcrudeoildisplacedby5%brinecontainingscaleorcorrosioninhibitorstoevaluatetheeffectofinhibitorsolutionsonthedisplacementefficiencyinthepresenceofcrudeoilwithoutasphaltenes.
Thirdseriesincludescorefloodingusingasphaltenicoilatasphalteneconcentrationof1%displacedby5%brine.Theseexperimentsrepresentthecorefloodingwithasphaltenicoilasareference.
Fourthseriesincludescorefloodingusingasphaltenicoilatasphalteneconcentrationof1%displacedby5%brinecontaining200ppmscaleorcorrosioninhibitors.
Theoil/waterrelativepermeabilityofthecoresampleswasdeterminedusingunsteadystatemethods.Therelativepermeabilityisoneoftheessentialelementsusedtoevaluatetheinfluenceofanyparameteronthemultiphasefluidflowthroughporousmedia.Relativepermeabilitycurvesareusuallyplottedasafunctionofwatersaturationandvarybetweenzeroandone.Themobileoilsaturationliesbetweentheirreduciblewatersaturation(Swi)andthewatersaturationatresidualoilsaturation(Swor).Therelativepermeabilityiscloseto1.0nearSwianddecreasesrapidlyasoilisdisplacedbywaterwhilethewaterrelativepermeabilityrisesgraduallyasthesaturationapproachesSwor.Therelativeflowoffluidsisafunctionofporesizedistribution;thereforeanychangeofthisdistributionduetoprecipitation,particlemovement,orphaseblockingwillchangetherelativepermeabilitycurves(CivanandDonaldson,1987).
However,inunsteadystatemethod,adrivingfluidataconstantratedisplacestheinsitufluid.Thepressuredropandfluidsaturationarerecordedwithrespecttotime.Relativepermeabilityvaluesoftheinsituandthedrivingfluidsarethencalculated.Differentmethodsareavailabletocalculatetheoil/waterrelativepermeability,suchasJohnson–Bossler–Naumann(JBN),Welge,andJones–Roszellemethods(Castanoetal.,2002;ZekriandEl-Mehaideb,2002;MohamadIbrahimandKoederitz,2001;Tothetal.,2001).Inthisstudy,theJBNmethodwasused(Johnsonetal.,1959).Toapplythismethod,p
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