石油工程双语版课件02石油地质及储油层

Chapter2

PetroleumGeologyandReservoirsReservoir(储油层)Wemaydefineareservoirasanaccumulationofhydrocarboninporouspermeablesedimentaryrock.Theaccumulation,whichwillhavereachedafluidpressureequilibriumthroughoutitsporevolumeatthetimeofdiscovery,isalsosometimesknownasapool.Ahydrocarbonfieldmaycompriseseveralreservoirsatdifferentstratigraphichorizonsorindifferentpressureregimes.23

Field

4Lease

5Reservoir(储油层)

具有商业价值的石油(及天然气)地层--reservoir，所需具备之条件

(1)合适之地层形貌(Shape/Configuration-traps)(2)顶盖层(caprock,rockseal)(3)储油层之面积(area)大

(4)储油层之厚度(thickness)大

(5)储油层之孔隙率(porosity)大

(6)储油层之含水饱和度(watersaturation)小

(7)储油层之渗透率(permeability)大6原油现地藏量

Originaloilinplace(OOIP)OOIP=A*h**(1-Sw)*1/BowhereA=储油层之面积(area)h=储油层之厚度(thickness)

=储油层之孔隙率(porosity)

Sw=储油层之含水饱和度(watersaturation)Bo=石油地层体积因子(oilformationvolumefactor)7原油现地藏量

Originaloilinplace(OOIP)OOIP=7758*A*h**(1-Sw)*1/Bowhere

OOIP=原油现地藏量,STB

A=储油层之面积(area),acresh=储油层之厚度(thickness),ft

=储油层之孔隙率(porosity),fraction

Sw=储油层之含水饱和度(watersaturation),fractionBo=石油地层体积因子(oilformationvolumefactor),bbl/STB1acres=43560ft21bbl=5.61458ft38资源量及蕴藏量定义资源量

(PetroleumResources，或Resources，或TotalPetroleuminplace，或Originaloilinplace)

在一区域或矿区所存在的石油（含天然气）之总量，称为资源量。蕴藏量(PetroleumReserves，或Reserves)

在一已知区域或矿区中，自某一时间点开始，依据当时的经济条件(E)、工程技术(F)、及地质条件(G)下，在可预见的未来所能采收的石油（含天然气）之量称为蕴藏量，或最终采收量。9Reserves(蕴藏量)

Reserves=OOIP*recoveryfactorwhereOOIP=A*h**(1-Sw)*1/Borecoveryfactor(采收因子)=f(k,E,P,T…)k=permeability(渗透率)

Thesettingforhydrocarbonaccumulationisasedimentarybasinthathasprovidedtheessentialcomponentsforpetroleumreservoiroccurrence,namely(a)asourceforhydrocarbons,(b)theformationandmigrationofpetroleum,(c)atrappingmechanism,i.e.,theexistenceoftrapsinporoussedimentaryrockatthetimeofmigrationandinthemigrationpath.Thediscoveryofoilbyexplorationwelldrillinginsomeoftheworld’ssedimentarybasinisshowninFigs.2.1and2.2Lowerrightline(0.1103m3oil/km2)/(100

willcatwells/104km2)=104m3oil/willcatwell=6.289*104bbl3oil/willcatwellUpperleftline(10103m3oil/km2)/(1

willcatwell/104km2)=108m3oil/willcatwell=6.289*108bbloil/willcatwellLowerrightline(0.01106m3oildiscovered/willcat)/(1106m3oildiscovered/successfulwildcat)=1%successfulwildcat/willcatUpperleftline(0.1106m3oildiscovered/willcat)/(0.1106m3oildiscovered/successfulwildcat)=100%successfulwildcat/willcat15现今的石油钻井很安全；很多国家都有制定法令以保护地表及地下之自然环境。在七个探勘井中会有一口具有生产利润的生产井对于不具生产价值的井，必须用水泥及泥土将井口封闭起来16PetroleumGeologyGeology(地质)---研究(1)地球的历史及构造(2)记录在岩石的生物(命)形式PetroleumGeology(石油地质)---研究地质以预测石油累积之处所17地球的历史及构造地球的形成—40～50亿年前由宇宙尘(Cosmicdust)的凝结而成地球内部大构造—Core---heavy(4,400miles)Mantle---Lighter(1,800miles)Crust---10~30miles18地球内部大构造19在地球上，不管您走到哪里，你都是在岩石（Rock）的上面。在某些地方，你是站有岩石的上面20哩处20哩是多少?6MILES=9.6KILOMETERS20MILES=32KILOMETERS喜马拉雅山大约有6哩高所以20哩是喜马拉雅山的3倍高，其间有很多的岩石。20地球表面的变化--RockcycleMagma(岩浆)Igneousrocks(火成岩)Sediments(沉积物)SedimentaryrocksMetamorphicrocks地球内部WatervaporandgasesPrimeval(初期的)Atmosphere(大气)地壳冷却地壳收缩变形而皱摺喷出形成heatheatpressureerosionerosionpressurecementationerosion下雨21ReservoirRockReservoirRockProrsityPermeabilitySandstones(SiO2)CarbonatesLimestones(CaCO3)Dolomites(CaCO3,MgCO3)ClasticChemicalOrganicOtherConglomerateSandsonteSiltstoneShaleCarbonateEvaporitePeatCoalDiatomiteLimestoneChertLimestoneDolomiteGypsumAnhydriteSaltPotash22沉积岩的分类

ClasticChemicalOrganicOtherConglomerateSandsonteSiltstoneShaleCarbonateEvaporitePeatCoalDiatomiteLimestoneChertLimestoneDolomiteGypsumAnhydriteSaltPotash碎屑岩化学岩有机岩其他砾岩砂岩粉砂岩页岩碳酸盐蒸发岩泥炭煤硅藻土石灰岩角岩石灰岩白云石石膏硬石膏盐岩碳酸钾(钾化合物)23地球的历史寒武纪(Cambrian)【约5.5亿年前】开始在海洋里有大量的生物(生命)

在寒武纪之前为前寒武纪(Precambrian)地质年代自寒武纪开始

>地质代年表(GeologicTimeScale)泥盆纪(Devonian)时期【约3.3亿年前】陆上有大量植物及动物24GeologicalTimeScale25Petroleumaccumulation

(石油累积)Petroleumaccumulation(石油累积)必须具备

(1)Oil＆gas之来源

(2)具有孔隙(porosity)及渗透率(permeability)之ReservoirRock(3)要有trap(封闭)以阻挡流体的流动26石油的来源－石油来自沈积岩的有机物质－海洋里大量的生物不停的，缓慢的掉落到海底。虽然在掉落的过程中，有部分被吃掉或被氧化掉，但另部份(动物或植物)掉落海底而埋在沼泽或泥泞之海底－海底继续被Sand(砂)，Clay(土)及debris等沈积物埋没一直到几千英呎－沈积物的压力开始作用。细菌由残余的有机物质中，用掉氧而分解物质，使其仅存碳及氢－在高度的压力及重量的地层影响之下，

Clays变成Shales→石油产生27

Petroleumformationrequiresthatorganicsourceclaysbecomematurebysubjectiontopressureandtemperature.

28石油形成的重要条件225℉<temperature<350℉有利条件

temperature<150℉不可能形成石油

temperature>500℉有机物质碳化，不能形成石油2930

Prolongedexposuretohightemperatures,orshorterexposuretoveryhightemperatures,mayleadprogressivelytothegenerationofhydrocarbonmixturescharacterizedascondensates,wetgasesandgas.Theaverageorganiccontentofpotentialsourcerocksisabout1%byweight.TheKimmeridgeclay,theprincipalsourcerockforNorthSeaoilaverageabout5%carbon(~7%organicmater)withlocalrichstreaksgreaterthan40%.Thehydrogencontentoftheorganicmattershouldbegreaterthan7%byweightforpotentialasanoilsource.31

Itisaruleofthumbthatforeachpercentagepointoforganiccarboninmaturesourcerocks,some1300~1500cubicmetersofoilperkm2-m(or10~40barrelsofoilperacre-ft)ofsedimentcouldbegenerated.Itisnot,however,necessarilytruethatalltheoilgeneratedwillbeexpelledortrappedinporousrock.32石油移栖石油形成后Traps＆ReservoirRocksMigration经过porousbed有permeability由于CompactionofSourcebedThemigrationprocessinvolvestwomainstages,namelythroughthesourcerockandthenthroughapermeablesystem.33Migrationofpetroleum

--throughthesourcerock

**Capillaryeffect**Microfractures

Sincethegenerationofpetroleumisaccompaniedbyvolumechangeswhichcanleadtohighlocalpressures,theremaywellbeaninitiationofmicrofractureswhichprovideanescaperouteintopermeablesystemssuchassedimentaryrocksorfaultplanes.Thesourcerockmicrofracturesarebelievedtohealaspressuresaredissipated.34石油移栖石油形成后Traps＆ReservoirRocksMigration经过porousbed有permeability由于CompactionofSourcebed35Migrationofpetroleum

--throughapermeablesystem**Fluidpotentialgradientorgravityeffect

Inthepermeablesystemthetransportoccursunderconditionsofafluidpotentialgradientwhichmaytakethehydrocarbontosurfaceortosomeplacewhereitbecomestrapped.Itmightbeassumedthatlessthan10%ofpetroleumgeneratedinsourcerocksisbothexpelledandtrapped,asshownintheexampleofFig.2.5.3637PetroleumtrapsThecharacteristicformsofpetroleumtrapareknownasstructuraltraps(构造封闭)and

stratigraphictraps(地层封闭),

withthegreatmajorityofknownaccumulationbeingintheformerstyle.38地质构造（GeologicalStructures）Erosion－SedimentationUplift－wearingdownUppercrustmoveUpwarddownwardFaultNormalReverseThrustLateralStrataorbedUnconformity－disconformity－AngularunconformityFoldsArches(orupfold)→anticlinesTraughs(ordownfold)→synclinesImportanttopetroleumaccumulation39

Figure1.12.Twogeneralkindsofunconformitiesaredisconformity(A)andangularunconformities(B)and(C).造山运动之应力所造成沉积过程所造成Figure1.13.Basichydrocarbonreservoirsarestructuraland/orstratigraphictraps.40

封闭(traps)

封闭(traps)Structuraltraps－anarcheduppersurfaceStratigraphictraps---up-dipterminationofporosity(permeability)StructuraltrapsAnticlinetrapFaulttrapDomeandplugtrapStratigraphictrapsUnconformitytrapsLenticulartrapDisconformityAngularunconformityCombinationtraps41Caprock

Impermeablerocksprovidesealaboveandbelowthepermeablereservoirrocks.

Atequilibriumconditions,thedensitydifferencesbetweentheoil,gasandwaterphasescanresultinboundaryregionsbetweenthemknownasfluidcontacts,i.e.gas-oilandoil-watercontacts.42Structuraltrapa(构造封闭)

--AnticlineLongitudinalviewofatypicalanticline.Theoilcannotescapeupwardbecauseoftheimperviousshalebedabovetheoilsand;neithercanittraveldownwardbecauseofthewaterthatisassociatedwithanaccumulationofthistype.Anticlines－Ofthemanytypesofstructuralfeaturespresentintheupperlayersoftheearthscrustthatcantrapoil,themostimportantistheanticlines－thetypeofstructurefromwhichthegreaterpartoftheword’soilhasbeenproduced.

Anticlinesareupfoldsofbedsintheearth’scrust,and,whentheproperconditionsarepresent,oilaccumulateswithintheclosureoftherefolds.43Structuraltrap--Anticline

Lateral,orendview,ofatypicalanticline.Planviewofatypicalanticline,showinglocationsoflongitudinalviewA-BandlateralviewC-D.44StructuraltrapsFigure1.7.Schematiccrosssectionshowsdeformationofearth’scrustbybuckingoflayersintofoldsFigure1.8.Simplekindsoffoldsaresymmetricalanticline(A),plungingasymmetricalanticline(B),plungingsyncline(C),anddomewithdeepsaltcore(D).Figure1.9.SimplifieddiagramoftheMilano,Texas,fault.45Structuraltraps–dome&anticlineFigure1.15.Oilaccumulatesinadome-shapedstructure(A)andananticlinaltypeoffoldstructure(B).Ananticlineisgenerallylongandnarrowwhilethedomeiscircularinoutline.(CourtesyofAmericanPetroleumInstitute)4647Structuraltraps--faultsFigure1.10.Simplekindsoffaultsarenormal(A),reverse(B),thrust(C),andlateral(D).Figure1.11.Variationsofnormalandreversefaultingarerotationalfaults(A)andupthrustfaults(B).48StructuraltrapsFigure1.14.Commontypesofstructuraltraps49Structuraltrap–fault&anticlineFigure1.17.Showninmapview,faulttrapsmaybesimple(A)orcompound(B).Figure1.16.Gasandoilaretrappedinafaulttrap-areservoirresultingfromnormalfaultingoroffsettingofstrata.Theblockontherighthasmovedupfromtheblockontheleft,movingimperviousshawloppositethehydrocarbon-bearingformation.(CourtesyofAmericanPetroleumInstitute)50Stratigraphictraps

(地层封闭)51

Figure1.12.Twogeneralkindsofunconformitiesaredisconformity(A)andangularunconformities(B)and(C).造山运动之应力所造成沉积过程所造成Figure1.13.Basichydrocarbonreservoirsarestructuraland/orstratigraphictraps.52StratigraphictrapsUnconformity

－Disconformity

－AngnlarunconformityPinctoutSandlensesChangesinsedimentation53

Figure1.22.Oilistrappedunderanunconformity.(CourtesyofAPI)Figure1.23.Lenticulartrapsconfineoilinporouspartsoftherock.(CourtesyofAPI)54StratigraphictrapAnexampleofastratigraphictrapwheretheoilzonepinchesout.Astratigraphictrapwheresandlensesareinterspersedinashalebed.Theshaleactsasapermeabilitybarrier55StratigraphicTrapsAstratigraphictrapwherechangesinsedimentationactasapermeabilitybarrier.Anangularunconformityasanoiltrap.Theflat-lyingshalebedabovetheoilzonesactsasapermeabilitybarrier.56StratigraphictrapsStratigraphictrapsresultwhenadepositionalbedchangesfrompermeablerockintofine-grainimpermeablerock(Fig.2.8).5758CombinationtrapsManyreservoirsexistastheresultofacombinationofstructuralandstratigraphicfeatures.IntheVikingGrabenareaofthenorthernNorthSea,theBrentSandreservoirsarecharacteristicallyfaulteddeltaicsandstruncatedbytheCretaceousunconformity.59Reservoirfluidsandpressure

Fromapetroleumengineeringperspectiveitisconvenienttothinkofsedimentarybasinsasaccumulationswaterinareasshowsubsidenceintowhichsedimentshavebeentransported.61ReservoirfluidsandpressureReservoirfluidsGasOilwaterWater─connatewater(connateinterstitialwater)Freewater~AquiferBottomwaterEdgewaterGasSolutiongasFreegasReservoirpressures

Hydrocarbonreservoirsarefoundoverawiderangeofpresentdaydepthsofburial,themajoritybeingintherange500–4000mss.Inourconceptofthepetroliferoussedimentarybasinasaregionofwaterintowhichsedimenthasaccumulatedandhydrocarbonshavebeengeneratedandtrapped,wemayhaveanexpectationofregionalhydrostaticgradient.PressuregradientequationInawatercolumnrepresentingverticalporefluidcontinuity,thepressureatanypoint(Px)isapproximatedbytherelationship

Px=X．GwwhereX=thedepthbelowareferencedatum(suchassealevel)

Gw=thepressureexertedbyunitheightofwater,orpressuregradient

Gw=f(T,salinity)

Gw=0.433psi/ft(or9.79kpa/m)forfreshwater

Gw=0.44psi/ft(10kpa/m)~0.53psi/ft(12kpa/m)forreservoirwatersystemPressuregradientrangesInreservoirfoundatdepthbetween2000mSSand4000mSS,wemightuseagradientof11kpa/mtopredictporefluidpressuresaround220barsto440bars.65ReservoirpressureReservoirpressureNormalpressureAbnormalpressure

－Artesianeffect6667

Theprimarydepositionalprocessesandthenatureofthesedimentshaveamajorinfluenceontheporosityandpermeabilityofreservoirrocks.68

Secondaryprocesses,includingcompaction,solution,chemicalreplacementanddiageneticchanges,canacttomodifyfurthertheporestructureandgeometry.Withcompaction,grainsofsedimentaresubjecttoincreasingcontactandporefluidsmaybeexpelledfromthedecreasingporevolume.Iftheporefluidscannotbeexpelled,theporefluidpressuremayincrease.AbnormalpressureUndercertaindepositionalconditions,orbecauseofmovementofclosedreservoirstructures,fluidpressuresmaydepartsubstantiallyfromthenormalrange.OneparticularmechanismresponsibleforoverpressureinsomeNorthSeareservoirsistheinabilitytoexpelwaterfromasystemcontainingrapidlycompactedshales.AbnormalpressureregimesareevidentinFig.2.11.AbnormalhighpressureAllshowsimilarsalinitygradientsbutdifferentdegreesofoverpressure,possiblyrelatedtodevelopmentinlocalizedbasins.Anyhydrocarbonbearingstructureofsubstantialreliefwillexhibitabnormallyhighpressureatthecrestwhenthepressureatthehydrocarbon-watercontactisnormal,simplybecauseofthelowerdensityofthehydrocarboncomparedwithwater.72Arethewaterbearingsandsabnormallypressured?

Ifso,whateffectdoesthishaveontheextentofanyhydrocarbonaccumulations?732.3Fluidpressuresinahydrocarbonzone74HydrocarbonpressureregimesInhydrocarbonpressureregimes

psi/ft

psi/ft

psi/ft75PressureKickAssumesanormalhydrostaticpressureregimePω=0.45×D+15Inwaterzoneat5000ftPω(at5000)=5000×0.45+15=2265psiaatOWC(5500ft)Pω(atOWC)=5500×0.45+15=2490psia76PressureKickInoilzonePo=0.35xD+CatD=5500ft,Po=2490psi

→C=2490–0.35×5500=565psia→Po=0.35×D+565atGOC(5200ft)Po(atGOC)=0.35×5200+565=2385psia77PressureKickIngaszonePg=0.08D+1969(psia)at5000ftPg=0.08×5000+1969=2369psia

78PressureKickIngaszonePg=0.08D+CAtD=5500ft,Pg=Pω=2490psia2490=0.08×5500+CC=2050psia→Pg=0.08×D+2050AtD=5000ftPg=2450psiaOverburdenpressureThereisabalanceinareservoirsystembetweenthepressuregradientsrepresentingrockoverburden(Gr),porefluids(Gf)andsedimentgrainpressure(Gg).Theporefluidscanbeconsideredtotakepartoftheoverburdenpressureandrelievethatpartoftheoverburdenloadontherockgrains.

Gr=Gf+GgOverburdengradientThemagnitudeoftheoverburdengradientisapproximately1psi/ft(22.6kpa/m).

For100%rock(sand)Gg=0.433x2.7=1.169psi/ftFor100%waterGf=0.433psi/ftFor

=20%rockGr=0.2x0.433+0.8x1.169=1.022psi/ftCausesofabnormalpressureAbnormalfluidpressuresarethosenotininitialfluidequilibriumatthediscoverydepth.Magara(1978)hasdescribedconditionsleadingtoabnormallyhighandabnormallylowpressures.Someexplanationslieinreservoirsbeingfoundatpressuredepthshigherorlowerthanthedepthsatwhichtheybecamefilledwithhydrocarbon.Thismaybetheresultofupthrustordownthrownfaulting.CausesofabnormalpressureOverpressurefromtheburialweightofglacialicehasalsobeencited.InGulfcoastandNorthSeareservoirs,overpressureismostfrequentlyattributedtorapiddepositionofshalesfromwhichboundwatercannotescapetohydrostaticequilibrium.Thisleadstooverpressuredaquifer-hydrocarbonsystem.FluidPressureRegimes

Thetotalpressureatanydepth=weightoftheformationrock+weightoffluids(oil,gasorwater)[=]1psi/ft*depth(ft)FluidPressureRegimes

DensityofsandstonePressuregradientforsandstonePressuregradientforsandstoneOverburdenpressureOverburdenpressure(OP)=Fluidpressure(FP)+Grainormatrixpressure(GP)OP=FP+GPInnon-isolatedreservoirPW(wellborepressure)=FPInisolatedreservoirPW(wellborepressure)=FP+GP’whereGP<=GPInaperfectlynormalcase,thewaterpressureatanydepthNormalhydrostaticpressureInaperfectlynormalcase,thewaterpressureatanydepthAssume:(1)Continuityofwaterpressuretothesurface(2)Salinityofwaterdoesnotvarywithdepth.

[=]psia

psi/ftforpurewater

psi/ftforsalinewaterAbnormalhydrostaticpressure

(Nocontinuityofwatertothesurface)[=]psiaNorma