石油地质学英文课件Chapter-1

Chapter1CrudeOil,NaturalGas,OilfieldWaterCrudeoilsNaturalgasesOil-fieldwaters1Crudeoils1.1Definition1.2Chemicalproperties1.3Distillation1.4Classification1.5Thedifferencesbetweenmarineand

terrigenousoils1.6Physicalproperties1.1DefinitionCrudeoilisdefinedasamixtureofhydrocarbonsandnon-hydrocarbons

thatexistspredominantlyasliquid,withvaryingamountsofdissolvedgasesand/orsemisolidhydrocarbonsinnaturalundergroundreservoirs.1.1DefinitionThewordpetroleumoriginatesfromtheLatinwordspetra(“rockandstone”)and

oleum(“oil”),justlike

itsChineseword,石油means“石”and“油”.Petroleumisakindofmineralresourcesthatoccursintheearthasgas,liquid,semi-solidsorinmorethenoneofthesestates.

Liquidpetroleumiscalledcrudeoilthatconsistschieflyoftheliquidhydrocarbons,withvaryingamountsofdissolvedgases,bitumens,andimpurities,whichcanbeproducedfromundergroundreservoirrocksthroughadrillpipe.GeneralFeaturesChemicallyanyliquidpetroleumisanextremelycomplexmixtureofhydrocarboncompounds,withvaryingamountsofnon-hydrocarboncompoundsofnitrogen,sulfur,oxygenandalsovanadium(V)andnickel(Ni)asimpurities.Theproportionsofthehydrocarbonconstituentsandthecontaminantsaredifferentinvariouspetroleumaccumulationsoroilfields.Thephysicalpropertiesofpetroleumaredifferentinvariousaccumulations/fields.1.2Chemicalproperties(1)Elementalcomposition

ThemainelementsareCarbonandHydrogen;TheminorelementsareSulfur,NitrogenandOxygen(normallylessthan3%);Traceelementsareheavymetals,suchasVandNi.NaturalGasCrudeOilAsphaltCoalKerogenCarbon7684.5(83-87)848379Hydrogen2413(11-14)1056Sulfur01.5(<1%)315Nitrogen00.5(<0.2)112Oxygen00.5(0.1-4.5)2108total100100100100100Thetablebelowshowstheelementalcontentsinnaturalgas,crudeoil,asphalt,coalandkerogen(2)Alkaneseries—ParaffinsThegeneralformulaisCnH2n+2.C1-4aregases.methane/CH4,ethane/C2H6， propane/C3H8,butane/C4H10C5-20areliquids.C20+areusuallywaxysolids.InCnH2n+2incrudeoil,usuallyn≤80.Alkaneseriescanbedividedinto2types:a.thenormalalkanes:n-alkanes

b.theisomericarkanes:i-alkanesMethaneEthanePropaneButanePentaneHexaneHeptane(3)NaphtheneorCycloparaffingeneralformular:CnH2nn≥5TheCycloparaffinsthatareformedbyjoiningthecarbonsinringarethemostcommonmolecularstructuresincrudeoils.Themostcommonnaphthenesincrudeoilaremethylcyclopentaneandmethylcyclohexane.Theaveragecontentofnaphthenesisabout50%incrudeoils,withthequantitiesincreasingintheheavierfractionsanddecreasinginthelighterfractions.Naphthenes(4)AromaticHydrocarbonsWithgeneralformularCnH2n-6;Thetermaromatichydrocarbonoriginatedfrompleasant-smellingcompoundsincrudeoils.HowevermostHCshaveverylittleodorinpurestate.AllaromaticHCscontainatleastonebenzenering.TheyareunsaturatedcycloHCserieswithdoublebondsbetweencarbonatoms,likesbenzeneanditshomologous:BenzeneNaphthaleneParanaphthalene(5)Nitrgen,sulfur,oxygencompounds(Asphaltics)Theyarecomplexstructuralarrangementsmadeofnaphtheno-aromaticnucleiwithchainsandheteroatoms(O,N,S).Sulfurcompounds：an

averagecontentofsulfurincrudeoilsis0.65%byweight.Loworhighsulfurcrudeoil:S<1.0%,S>1.0%b)Nitrogencompounds：Nitrogencontentisusuallymuchlowerthansulfurcontentincrudeoils.Theaveragenitrogencontentis0.094%bywt,inmostcrudeoilsnitrogencontentislessthan0.2%.Themostimportantnitrogencompoundisporphyrin:Nickel(Ni)andVanadium(V)porphyrin.c)Oxygencompounds:assaturatedfattyacids:phenolsAboutporphyrinPorphyrinsarecharacterizedbyatetrapyrrolicnucleus(4pyrrolerings),probablyinheritedfromchlorophyllorhemin.

Sonickelporphyrinandvanadiumporphyrinarebiologicalmarkersindicatingcrudeoilsderivedfromorganicmatters.Chlorophyll,thegreenphotosyntheticpigmentofplants.Hemin,theredpigmentofanimalblood.Thereareothermetals,likeiron(Fe),zinc(Zn),copper(Cu),lead(Pb),arsenic(As),molybdenum(Mo),cobalt(Co),magnesium(Mg),chromium(Cr)etcincrudeoils,butonlyaverylittleamount.1.3Distillationanduses

Distillationistheprincipalmethodforseparatingcrudeoilsintousefulproducts.Thecommondistillatefractionsare:Gasoline(C5-C10)Kerosine(C11-C13)Dieseloil(C14-C18)Heavygasoil(C19-C25)Lubricatingoil(C26-C40)Residuum(>C40)Adistillationtower

Arefinerytowerisequivalenttoaseriesofindividualdistillationflasks,inwhichthedistillatefractionsfromthefirstflaskiscondensedinthesecondflask,andthenredistilledtoproduceadistillateforthethirdflask.AromaticsNaphthenoaromaticsNitrogen,sulfur,andoxygencompoundsThelightgasolinefractionofoilisdominatedbythenormal,iso-,andcycroparaffins.FromGasolineintotheheavierfractions,ThereisamarkedincreasesintheAromatics+naphthenoaromatics.

AromaticsNaphthenoaromaticsNitrogen,sulfur,andoxygencompoundsAfterdiesel,NSOcompoundscontentincreasesmarkedly,theresiduumisdominatedbyNSOcompounds.1.4ClassificationSomeclassificationshavebeenproposedbygeochemistsandoilrefiners.AclassificationofpetroleumhasbeenproposedbyTissotandWelte(1978)basedprimarilyonthecontentsofthevariousstructuraltypesofhydrocarbons:P=ParaffinN=Naphthenes

AA=AromaticsandAsphaltenes+resinsS=Saturatedhydrocarbon1)S>50%,AA<50%,P>40%,P>N:Paraffinicoils2)S>50%,AA<50%,N>40%,N>P:Naphthenicoils3)S>50%,AA<50%,P≦40%,N≦40%:

Paraffinic-naphthenicoils4)S≦50%,AA≧50%,P>10%:Aromaticintermediateoils5)S≦50%,AA≧50%,P≦10%,N≧25%:Aromaticnaphthenicoils6)S≦50%,AA≧50%,P≦10%,N≦25%:AromaticAsphalticoils

ParaffinicNaphthenicParaffinic

–naphthenicAromaticintermediateAromaticnaphthenicAromaticAsphalticP=ParaffinN=NaphthenesAA=AromaticsandAsphaltenes+resins2540505040605060901075OnoiltypesOnwaxcontentsOnsulfurcontentsOntraceelementalcontents,asV,Ni,V/NiOnstableisotopesofcarbon1.5Thedifferencebetweenmarineand

terrigenouscrudeoils1.6Physicalproperties1)DensityandSpecificGravity2)ViscositySmell3)Fluorescence4)Color5)Smell6)CalorificValues1)DensityandSpecificgravity

Oildensityisusuallylessthan1000kg/m3,oilislighterthanwater.Butsomecrudeoils,denseoils,canheavierthanwater,theirdensitycanlargerthan1000kg/m3.Toproducedenseoilisverydifficult.

Viscosityisaninversemeasureoftheabilityofasubstance(fluid)toflow.Thegreaterviscosityofafluid,themoredifficultitflows.Oilviscosityisgenerallydependentchieflyontheamountofgasdissolvedinitandonthetemperature.2)Viscosity3)

Fluorescence

Alloilsexhibitmoreorlessfluorescence,thearomaticoilsarethemostfluorescent.Fluorescentcolorofcrudeoilscanbeyellow,green,orblue.Fluorescencemustbeobservedunderultravioletradiation.Fluorescenceisusedinwellloggingtolocateoilshowingincores,cuttings,anddrillingmuds.4)Color

5)Smell

6)CalorificValue

2NaturalGases2.1Concepts2.2Chemicalcompositions2.3Physicalproperties2.4Aboutgashydrate2.1ConceptsPetroleumgas,commonlycallednaturalgasorhydrocarbongas,consistsofthelighterparaffinhydrocarbons,ofwhichthemostabundantismethanegas(CH4).Intheoilindustry,naturalgasisdefinedasamixtureofhydrocarbonsandvaryingquantitiesofnon-hydrocarbconsthatexistseitherinthegaseousphaseorinsolutionwithcrudeoilinundergroundreservoirs.

2.1Concepts

Associatedgas:thegasoccurswithoil.

Non-associatedgas:thegasoccursalone.

Aggregatedgas:Thegasingasreservoir,Condensedgas.Thegasinoilandgasreservoir.

Decentralizedgas:Thegasdissolvedinoil,thegasdissolvedinoil-fieldwaters,theliquefiedgas,thecoalbedgas,andthemethanehydrate.2.2Chemicalcompositions1.

Hydrocarbongas: Methane/CH4,maincompositionofgas Ethane/C2H6, Propane/C3H8,takesvariousamountsingas Butane/C4H102.Non-hydrocarbongas: N2,CO2,H2S,H2,CO,SO2,Hg,etc.SourGas(%)Frequency(%)HydrogenGas(%)HydrocarbonGas(%)2.3Physicalproperties1DensityandspecificgravityofnaturalgasDensitymeanstheweightofagivenvolume,suchaskilogramspercubicmeter.Thedensityofanaturalgasdependsonitspressure(p),temperature(t),apparentmolecularweight(m)andcompressibilityfactor(z).Dg=0.1196571×p×mg/(z×t)Thedensityofnaturegasunderthereservoirconditionislargerthanthatofstandardgas,usually150–250kg/m3.Thespecificgravityofnaturalgasmeanstheratioofnaturalgasdensitytothatofair(28.97).Alsotheratioofmolecularweightofnatural

gastothatofair:

rg=mg/28.972Thesolubilitya.inwater

Henlyformula:Q=C*P

Q:solubility,C:solutioncoefficient,P:pressure.

b.incrudeoilthesolubilitydependsonthepressure,temperature,compositionofgas,thecontentoflightHCincrudeoils.2.4Aboutthegashydrate(Justforreference)Gashydratesarecrystallinecompoundsinwhichtheicestructureofwaterisdistortedtoformcagesthatcontainthegasmolecules.Thehydratesaresolidsresemblingwetsnowinappearance,andtheyformbothaboveandbelow0℃underspecificpressure-temperatureconditions.Thewatermoleculesformtwokindsofunitcellstructures.Thesmallerunitstructurecontains46watermolecules,whichcanholdupto8methanemolecules.GasessuchasCH4,C2H6,H2S,andCO2canfitintothisstructure.Thelargerunitcellcontains136moleculesofwater.Gasessuchaspropaneandiso-butanecanfitintoit.Thesearetheonlygaseoushydrocarbonsthatformhydrates.Thepentanesandn-butanemoleculesaretoolarge.Amethanehydrateinwhichalltheicestagesarecompletelyfilledwithmethanecontainsabout172m3CH4ofhydrateatSTP.Innaturethemoretypicalratiois40m3CH4/m3ofhydrate.NaturalhydrateunitsgenerallyhavesixorsevenH2OmoleculesperCH4molecule.Thepressure-temperaturediagramformethaneanda0.6gravitygas(C1+C2+C3)isshowninFigure7-8.Hydratesareformedbyincreasingpressuresandaredecomposedbyincreasingtemperatures.Sincethepressurerequiredtoformgashydratesincreaseslogarithmicallyasthetemperaturesincreaselinearly,itisapparentthatthehydratesinmostsedimentarybasinsdecomposeinthetemperatureranging70to80℉(21to27℃),becausethepressuresareinadequatetopreservethem.Hydrateusuallyoccursinpermafrostterritory,polarregion,anddeepseabottomsediments.Itisestimatedthatthereisveryrichamountofhydratearoundtheworld.But,nowitisdifficulttoexploithydrateintechnical.3Oil-fieldWaters3.1Concepts3.2Sourceofoil-fieldwaters3.3Chemicalcompositionsanddegreeofmineralization3.4Classification3.1ConceptsOil-fieldwatersingeneralaretermed"brines".Thewaterfoundinpetroleumreservoirrocksisusuallyreferredtoas"interstitialwater",butitisimprobablethatthewaterwhichnowexistsintheporesofareservoirrockisthesamewaterwhichwasinthesamegroupofporesatthetimewhenthesedimentswerefirstlaiddown.Theexpressions"bottomwater"meaningwaterunderlyingtheoiland"edgewater“meanswaterlyingdowndipandthereforelaterallywithrespecttotheoilzone.Clearly,bothtermsareconcernedwiththesamebodyofwaterinagivenreservoirrock.Also,topwater,intermediarywaters.BottomwaterEdgewaterUnpermeablecoveringstrataUpperwaterInterbeddedwaterBottomwaterEdgewaterUnderlayerwaterIntermediarywaterphreaticwaterwaterbarrier3.2Sourceofoil-fieldwatersSedimentationwater:thewaterinwhichsedimentsweredeposited.Infiltrationwater:thewaterthathasfallenasrainwaterandhasfilleduptheporousandpermeablerocks.Transformwater:thewatertransformedfromclaymineralsororganicmatters.Plutonicwater:thewaterformedbymagmatismormetamorphism.

3.3Chemicalcompositionanddegreeof

mineralization1Inorganic:6kindsofion:

sodium(Na+)+potassium(k+),calcium(ca2+),magnessium(mg2+)

chlorides(Cl-),sulfates(SO42-),bicarbonates(HCO3-)+carbonates(CO32-),

andothertraceelements.3positiveions3negativeions2Organic:HC,Phenols,saltoforganicacid

Indeed,ithasbeenproposedthatalateralincreaseinthebenzenecontentofthebrineinagivenstratummaypointtowardsanoilaccumulationinthatstratum.3thegasdissolvedinoil-fieldwaterThedegreeofmineralizationIt’salsocalledconcentrationorsalinityofo