UnconventionalPetroleum Geology
SecondEdition
CainengZouetal. ResearchInstituteof PetroleumExploration&Development People’sRepublicofChina
Elsevier
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2.2 Sandy Debris Flow
2.3 lacustrine Carbonate Rock 108 Unconventional Petroleum
3. Types of Reservoirs 108 Techniques
3.1 Tight Sandstone Reservoirs 109
3.2 Mud Shale Reservoirs 115
Assessment Methods for 3.3 Tight Carbonate Reservoirs 118 5.
4. Microscale to Nanoscale Pore-Throat Unconventional Petroleum Systems
4.1 Microscale to Nanoscale Pore-
Throats
in China and Abroad
and Characteristics of 4.2 Nanoscale Pore-Throat Petroleum
4.3 Nanoscale Hydrocarbon
5. Mud Shale Pore Evaluation
5.1 Three-Dimensional Pore System Test
5.2 Nitrogen Adsorption Test
5.3 Controlling Factors for Pore Evolution
5.4 Mud Shale Pore-Throat Evaluation
Tight Sandstone Reservoir Evaluation
6.2 Diagenetic Evolution
6.3 Main Controlling Factors for Reserving
6.4 Evaluation of Tight Sandstone Reservoirs
4. Unconventional Petroleum
1. High-Quality Source Rock Systems 143
1.1 Type and Formation of Source Rocks 143
1.2 Evalualion Criteria for High-Quality
Rocks 145
Experimental Analysis
2. Continuous Petroleum Accumulation 147 Numerical Simulation Techniques
2.1 Concepts of Continuous Petroleum
Accumulation 147
2.2 Characteristics of Continuous
Petroleum Accumulation 148 Mechanism of Continuous Petroleum
Techniques for Testing the Absorbed 2.3
Contents of Coal and Shale 211 Accumulation 148
3. Evaluation of the Six Characteristics 151
7. Geophysical Techniques
3.1 Evaluation of Lithology, Oil Possibility, and Physical Properties 151 1. Logging Evaluation Techniques 213
3.2 Evaluation of Source Properties 156 1.1 Logging Evaluation of Source Rock
3.3 Evaluation of Brittleness 159 Quality 213
3.4 Evaluation of Geostress Anisotropy 160 1.2 Logging Evaluation of Lithology and 3.5 Case Study 162 Physical Properties 214
4. Method of Evaluating Sweet Spots 163 1.3 Logging Evaluation of Oil and Gas
4.1 Evaluation Criteria for Unconventional Possibility 217 Petroleum "Sweet Spots" 165 2. Reservoir Prediction Technology Based on
4.2 Main Evaluation Parameters for Tight Prestack Seismic Data 218 Oil Sweet Spots 165 2.1 Basic Theory of Prestack Seismic
4.3 Evaluation Parameters and Standards Inversion 219 for Tight Oil Sweet Spots 170 2.2 Main Technical Methods for AVO
4.4 Integral Evaluation Method for Tight Irwersion 221 Oil Sweet Spots 171 2.3 EI Inversion Techniques 222
Miscellany
2.1 Concept of Shale
2.2 Formation and Distribution of
in the San Juan Basin
Low.Ranking Coalbed Methane in Organic·Rich Shale 276 the Powder River Basin
2.3 Geochemistry of Organic·Rich Shale 282
3. Characteristics of Shale Reservoirs 284
3.1 Petrological Properties of Shales 284
Heavy Oil and Bitumen
3.2 Physical Properties of Shale 285 1. Summary
3.3 Oil and Gas Possibility of Shale 286 2. Physical and Chemical Properties of
3.4 Evaluation of Shale Reservoirs 287 Heavy Oil and Bitumen
2.1
3.3
5.2
Foreword
Thisbookprovidesasystematicdescriptionofthetheories,keytechnologies,andmaintypesofunconventionalpetroleum geologyafteranalyzingthedevelopmenttrendsinthepetroleumindustryalongwiththetheories,technologies,developmentprospects,andstrategicconsiderationsrelatedtounconventionalpetroleum.Thebookcomprisesthreeparts:Part 1, “EssentialsforUnconventionalPetroleumGeology,” includestheintroduction,aswellasintroducesthemeaningof unconventionalpetroleumgeology,unconventionalpetroleumreservoirs,andunconventionalpetroleumaccumulationand evaluation;Part2, “UnconventionalPetroleumTechnology,” describesunconventionalpetroleumresourceevaluation methods,experimentalanalysistechniques,geophysicaltechniques,andwell-drilling,andcompletiontechniques;andPart 3, “MiscellaneousUnconventionalPetroleum, ” coverstightoilandgas,shaleoilandgas,coalbedmethane,heavyoiland bitumen,oilshale,naturalgashydrate,andotherunconventionalpetroleumresources.Placingequalstressontheoretical systems,technicalmethods,andtypicalexamples,thisbookrepresentsacombinationofscienceandpracticalityinbothits contentandstructure.
Thisbookcanbeusedasatextbookforacademicandresearchinstitutesaswellasareferenceforpetroleumexplorers andresearchers.
FOREWORDI
Petroleumresourcescanbegroupedintotwobasictypes:conventionalandunconventional.Asdrillingandproduction processesadvance,thehistoryoftheoilandgasindustrycanbeorganizedintothreestages:conventionalpetroleum exploitation,conventional unconventionalpetroleumexploitation,andunconventionalpetroleumresourceexploitation. InChina,thedegreesofprovenconventionalpetroleumresources(includingtightgas)areonly36%foroiland16%for naturalgas.Thedegreeofprovenunconventionalpetroleumresourcesis2%forcoalbedmethane(CBM)andthe firststep forshalegasexplorationjuststarts.Asfarasresourcesareconcerned,petroleumcanstillmeetthedemandsofhuman societyatitscurrentrateofdevelopmentforaconsiderablelengthoftime.Thedevelopmentofunconventionalpetroleum willextendthelifeofthepetroleumindustryforanotherfewcenturies,offeringmankindsuf ficienttimetodevelop renewableandnewenergysources.
Theorycomesfrompractice,whichinturnservestheory.Theextensive,successfuldevelopmentoftightoilandgasin theOrdosBasinintheShaanxi-Gansu-NingxiaregionandInnerMongoliaprovidesexperiencesandlessonsforunconventionalpetroleumdevelopmentinChina.Afterindustrialoil flowwasyieldedbytheYan-1wellintheUpperTriassic YanchangFormationtightsandstonein1907,PetroChinaChangqingOilfieldCompany,ShaanxiYanchangOil field Company,andPetroChinaZhenjingOilfieldreportedanannualoilproductionof3547 104 tin2012.Thecumulativeoil productionis27,940 104 t.Thetotalnumberofproductionwellsismorethan100,000.In1989,Shaancan-1yielded industrialgas flowfromtheLowerOrdovicianMajiagouFormationlimestone.The1990switnessedanotherdiscoveryof extensiveLowerPermianShiheziFormationandShanxiFormationtightsandstonegasplays.The314 1012 m 3 gas producedin2012includes270 1012 m 3 oftightsandstonegasand44 1012 m 3 oflimestonegas.Thecumulativegas productionis1745 1012 m3.Morethan10,000gaswellshavebeenbuilt.In1997,PetroChinacompletedtheinstallation oftheShaanxi Beijinggastransmissionpipeline,registeringthestartofgassupplytoBeijing.ItisimperativeforChinato guidethedevelopmentofunconventionalpetroleumresourceswithasustainableoutlookandtoseeklow-costdevelopmentbycreatingadvanced,applicabletechniquesaccordingtothegeologicconditionsofeachindividualpetroliferous basin.
InanefforttopushforwardthedevelopmentofunconventionalpetroleumresourcesinChina,withthesupportofa state-of-the-artunconventionalpetroleumlaboratoryandbasedonyearsofresearchandinvestigation,Dr.Zoufromthe ResearchInstituteofPetroleumExploration&Development(RIPED)andhisresearchteampublishedthe firstandsecond editionsofUnconventionalPetroleumGeologyin2012(Beijing,GeologicalPublishingHouse)anditsEnglisheditionon Elsevierinthesameyear.Theseworksprovidesystematicdescriptionsofthemeaning,geologiccharacteristics,
distributionrules,resourcepotential,andexplorationanddevelopmenttechniquesofunconventionalpetroleum.In2013, Dr.Zouandhiscolleaguespublishedanarticleentitled “Geologicalconcepts,characteristics,resourcepotentialandkey techniquesofunconventionalhydrocarbon:Onunconventionalpetroleumgeology” in PetroleumExplorationand Development (Issue4).Inaddition,theauthorscommunicatedthetheoriesandtechnologiesforunconventionalpetroleum explorationinsideandoutsideofChinaatPetroChinapetroleumtrainingsessionsandresearchacademies.Congratulations onthepublicationofthisbook,whichoffersamasterpieceforChina’sunconventionalpetroleumprofessionals,academics, andenergyprofessionals.
LiDesheng AcademicianofChineseAcademyofScience
FOREWORDII
Dr.Zouandhiscolleagueshaveembarkedbeginningin2011onamajorefforttoputtogetheracomprehensivebook coveringoneofthetwomostimportantglobalaspectsofthefutureofpetroleumnamelyunconventionaloilandgas(the otheroneisinmyviewthechallengeofimprovedoilrecoveryinconventional fields).
Thegrowingdemandforenergyingeneraliscontinuouslygrowingduetothetwinfactorsofpopulationgrowthand improvedstandardoflivingworldwideandinChinaspeci fically.Asfaraspetroleumisconcernedtheemerging importanceofunconventionalresourcescannotbeoverstated,onlyaboutathirdoftheworld’soilandgasreservesare conventional,theremainderareinunconventionalresourcesincludingunconventionalresourcesliketightgassandsand carbonates,coalbedmethane(CBM),shalegasandoil,heavyoil/tarsands,andmethanehydrates.Theseresourcesare called “unconventional” becauseinordertoeconomicallyaccessandproducethemunconventionalmethodsandexpertise arerequired.
Mostimportantlyunconventionalhydrocarbonreservoirshavelowpermeabilityandporosityandsoaredifficultto produce.Oftenenhancedrecoverytechniques,suchasfracturestimulationorsteaminjectionetc.,mustbeperformed, makingtheprocessmoredifficultthanaconventionalplay.
UnconventionalPetroleumGeologywrittenbyDr.Zouandhiscolleaguesisabroad,updated,andatrulyunprecedentedoverviewofthekeytechnicalaspectsandprogressesofallunconventionalresourcesE&P,andtheirlatestprogressesonnanoporecharacterizationintightoil/gasandshaleoil/gasrocksinChina,hydrocarbonenrichmentand producingmechanism, “sweetspot” evaluation,andspatialdistributionandpredictionofpetroleumresources,allofwhich arefullofscientifi cvalueandpracticalsignificance.Thisbookpromisestoserveasthe firstcomprehensivetextbookever forgraduate/postgraduatestudies.TheappearanceofbothprospectiveEnglishandthisChineseversionwillmakethis uniquetextbookuseableworldwide.
IcongratulateDr.Zouandhisteamfortheirmajorcontribution.
AmosNur StanfordUniversity Member,USNationalAcademyofEngineering
Preface
Energy,water,andfoodconstitutethethreemajorfactorsonwhichmanreliesforexistence.Energyislikethepowerthat drivestheearthhumansforward.Petroleumislikethesensitivenervesoftheearthhumans.Manwillundergothreemajor energytransitions:from firewoodtocoal,fromcoaltopetroleum,andfrompetroleumtonewenergy.Withthecontinuouslyincreasingenergydemandsoftheworld’seconomyandsociety,internationaloilpricesrunningathighlevel,and theadventofalow-carbonsociety,thethirdtransitionfromconventionalpetroleumtonewenergyisinevitable.However, itwillbedifficultfornewenergytoliveuptoitsmissionwithinaforeseeableperiodoftime,anditwillhavetobe supplementedbyitsconventionalprimaryenergycounterparts(i.e.,oil,naturalgas,andcoal),withoilandgasstill contributingover50%ofallenergyinthefutureenergystructure.Threestagescharacterizethecurrentworldpetroleum industry:acontinuousdevelopmentstageforconventionalpetroleum,astrategicbreakthroughstageforunconventional petroleum,andagoldendevelopmentstageforpetroleumtechnologicalinnovation.
Bytype,petroleumresourcesincludeconventionalandunconventionalresources,whichare “orderlyaccumulatedand spatiallyparagenetic.” Anindustrialsystemfeaturingthecodevelopmentofconventionalandunconventionalpetroleum willtakeform.Thepetroleumindustrywillundergostagesofconventionalpetroleum,conventionalandunconventional petroleum,andunconventionalpetroleum,comprisingtheentirelifeexpectancyofthepetroleumindustry.Researchindicatesthatthetotalamountofconventionalandunconventionalpetroleumresourcesintheworldisapproximately 5 1012 toe,forwhichtheconventional-to-unconventionalratioisontheorderof2:8.Theformerareprimarily distributedintheMiddleEast,Russia,NorthAmerica,andSouthAmerica,whilethelatterarefoundinNorthAmerica, Asia/thePacifi c,SouthAmerica,andRussia.Sofar,therecoverypercentageofconventionalpetroleumresourcesismerely 25%,whilethatofunconventionalpetroleumresourcesisnegligible.Intermsofresources,petroleumcanstillmeetthe demandsforthedevelopmentofhumansocietyforaconsiderablelengthoftime.Asforecasted,thelifeexpectancyofthe petroleumindustrywillbemorethan300years.
Researchhasdisclosed10basicrulesunderlyingtheformationanddistributionofconventionalandunconventional petroleumintheworld:(1)theaccumulationofconventionalandunconventionalpetroleumisorderly,andtheyspatially coexist;(2)theTethysdomaincontrolstheformationanddistributionoftheworld’soilandgasenrichmentzones;(3) forelandbasinthrustzonescontrolthedistributionsoflargetectonicoilandgas fieldgroups;(4)intracratonicuplifts controlthedistributionsofsupergiantoilandgas fields;(5)platformmarginscontrolthedistributionsoflargebioreef flat oilandgas fieldgroups;(6)passivecontinentalmarginscontroltheformationanddistributionsofhugemarineoilandgas fields;(7)forelandbasinforedeepslopescontroltheoccurrenceoflarge-scaleheavyoilandbitumen;(8)basinsedimentary slopescontroltheaccumulationoftightoilandgasandCBM;(9)basindeep-water,organic-richsedimentscontrolthe detentionofshaleoilandshalegas;and(10)low-temperature,high-pressurebottomsedimentscontrolthedistributionof hydrate.
Theworldhasenteredintoanewstageofstableproductionforconventionalpetroleumandfastdevelopmentof unconventionalpetroleum.TwomajorconventionalpetroleumproductionareashavetakenformintheMiddleEastand CentralAsia/Russia.Abouttwo-thirdsoftheremainingrecoverablereservesandundiscoveredresourcesofconventional petroleumintheworldarefoundintheseregions,togetheraccountingfor63%ofthetotaloiland67%ofthetotalnatural gasintheworld.Theoilandgasproductionintheseunconventionalpetroleumproductionareashasseencontinuous growth,withtheoilsharerisingfrom43%in2000to49%in2013,andthenaturalgasshareincreasingfrom34%in2000 to40%in2013.Ontheotherside,twomajorunconventionalpetroleumstrategicdevelopmentareasarealsotakingformin theUnitedStatesintheWesternHemisphereandChinaintheEasternHemisphere.Majorbreakthroughshavebeenmade inunconventionalpetroleumexplorationanddevelopment,particularlyinthe fi eldsoftightgas,CBM,shalegas,andtight oil,withtheshareofunconventionalpetroleumproductionintheworld’stotaloilproductionquicklyincreasingtohigher than10%.
Thepast10yearsrepresentthegoldendecadeofrevolutionarydevelopmentforshalegasandtightoilintheUnited States,whereshalegashasachievedcontinuousmajordevelopmentsfromBarnetttoHaynesvilleinthesouthand Marcellusintheeast,makingtheseareashotspotsforunconventionalpetroleumdevelopment.In2013,shalegasproductionwas3100 108 m3,orabout45%ofthecountry’stotalnaturalgasproduction.Tightoilhasalsoseencontinuous majorbreakthroughsfromBakkeninthenorthandEagleFordacrosstoUticaintheeast,makingtheseareashighlightsfor unconventionalpetroleumdevelopment.In2013,thetightoilproductionwas1.4 108 t,orabout28%ofthecountry’s totaloilproduction.Therapiddevelopmentofunconventionalpetroleum(e.g.,shalegasandtightoil)hasledtheUnited Statestodependmuchlessonforeignoilandgas.Asamatteroffact,theUnitedStates’ externaldependencewasonly5% fornaturalgasand33%foroilin2013.Unconventionalpetroleumhascontinuedtopropeltheimplementationofthe country’senergyindependencestrategy.ItisquitepossiblethattheUnitedStateswillguaranteeitslocalenergysecurityby realizingenergyindependenceinabroadsense.
Thepast10yearsrepresenttheexploratorydecadeofgroundbreakingdevelopmentfortightgasandtightoilinChina. Tightgashasbecomeanimportantareaforincreasingthereservesandproductionofnaturalgas,withnewproven geologicreservesoftightgasoverthepast10yearsaveraging2760 108 m3,orabout45%ofthecountry’stotalproven reservesofnaturalgasduringthesameperiod.In2013,thetightgasproductionincreasedtoaround2760 108 m 3 ,or about29%ofthecountry’stotalnaturalgasproduction.TheSuligetightgasregion,thelargestofitskindinChina,was discovered.Asoftheendof2013,theprovenandroughlyprovengeologicreservewas3.9 1012 m3,andtheannual productionwas212 108 m3.(5 10) 108 t.Reserve-scaletightoilregionshavebeendiscoveredintheOrdos,Junggar, andSongliaoBasins.MajorbreakthroughshavealsobeenmadeintheBohaiwanandSichuanBasins.AsforCBM,ground productionbaseshavebeensetupintheSouthQinshuiBasinandOrdosBasin.In2013,thegroundCBMrecoverywas 30 108 m3.InitialindustrialbreakthroughshavebeenreportedforshalegasintheSilurianLongmaximarineshaleinthe SouthandEastSichuanBasin(thecoverofthisbookisanimageofnanoporesinorganicmatterfromWei-201,the first wellinChinathatdiscoveredshalegasin2010;poresize ¼ 100 200nm).In2013,theproductionwashigherthan 2 108 m3.Tightoilandtightgashavebecomethe fi rstpartofChina’sunconventionalpetroleumdevelopment.CBM andmarineshalegaswillcomeintolarge-scaleproduction.
Inthefuture,fourinnovationsareexpectedtodominatethetechnologicaldevelopmentoftheworld’spetroleumindustry:(1)higherrecoveryforoldoil fields;(2)landdeeppetroleum;(3)marinedeep-waterpetroleum;and(4)unconventionalpetroleum.Thetheoreticalandtechnologicalinnovationsrepresentedbytheshalegasrevolutionarefacilitating theentiretechnologicalrevolutioninunconventionalpetroleum.High-resolution3Dseismicexplorationandhorizontal wellvolumetricfracturinghavebecometwocoretechniquesforexploringanddevelopingunconventionalpetroleum. Multiwellplatform-basedfactoryproductionhasbecomeanewmodeloflow-costoilandgasproduction.
Thelarge-scaledevelopmentofunconventionalpetroleumhasbroughtaboutgreatchangesinpeople’sunderstanding ofpetroleumgeology,aswellasoilandgasexplorationanddevelopmenttechniquesandproductionmodels.Consequently,numerouslimitationsrelatedtotraditionalconventionalpetroleumgeologyhavebeenidentified:(1)thelimitation ofthephysicalpropertiesofreservoirs,whichisbasedontheknowledgethattightrocksandsourcerocksareallableto formeffectivereservoirs;(2)thelimitationofcaprocksealing,whichisbasedontheknowledgethattightreservoirscan serveasthecaprockthemselvesandwaterpotentialcanalsoprovidesealingfunctions;(3)thelimitationoftrap boundaries,whichisbasedontheknowledgethatmassstratiformreservoirbodiesareabletostorepetroleumandthattrap boundariesareinsignificant;(4)thelimitationofmigrationdynamics,whichisbasedontheknowledgethatbuoyancyis insigni ficant,sohydrocarbon-generatingpressurizationandcapillarypressuredifferencescanbethemainfactors influencingmigrationdynamics,whichgenerallyfollowtheNon-Darcy fl owlaw,andthedifferentialdistributionof oil gas waterisinsignifi cant;and(5)thelimitationofaccumulationlocations,whichisbasedontheknowledgethat unconventionalpetroleumistypicallyhostedinbasincenters,slopes,andothernegativetectonicunits.
Chinahasharvested10importantobservationsfromtheoreticalresearchonunconventionalpetroleumgeology. Speci fically,researchershavebeenable(1)tosuggestthathigh-qualitysourcerockscontrolthedistributionofmain unconventionalpetroleumandthatsource reservoirparageneticassemblagesarefavorablefortheoccurrenceofunconventionalpetroleum;(2)toestablishthegeneticdistributionpatternsoflargecontinentalopen-lakeshallow-water deltasrelativetosandydebris fl owsandtransitionalorganic-richshales,openingupnewareasoftightoilandgasand shaleoilandgasinbasinslopecenters;(3)todiscoverthemicro-tonanoscalepore throatsystemsofunconventionaltight reservoirs,whichcomprise70 90%ofthetotalnumbersofporesinsuchreservoirs,increasingthereservoirspaceand resourcepotentialofunconventionalpetroleum;(4)toestablishthemicro-tonanoscalepore throatstructuremodelofoil andgasaccumulation,revealtheaccumulationlawofunconventional, “continuous” petroleum,identifyits10differences fromconventionaltrappetroleum,andexpandtheareaofoilandgasexplorationanddevelopment;(5)tosuggestthat unconventionalpetroleumshouldbeevaluatedwithrespecttosixsourceproperties(lithology,physicalproperties,
brittleness,petroleumpossibility,andstressanisotropy)andtheirrelationshipswithoneanother,providingamethodology foridentifyingfavorableregions;(6)toestablishthemodelforselecting “sweetspots,” horizontalwellvolumetricfracturing,andplatform-based “factory” productionforunconventionalpetroleum,providingscientificproceduresfor explorationanddevelopment;(7)toestablishanL-curveandtheoreticalpredictionmodelforunconventionalpetroleum andrevealingthattherecoveryratesoftightoilandgasandshaleoilandgasarebeingimprovedmainlybyusingnew wellsinplaceofolderonesandbyemployingnewtechniques;(8)toformasoftwaresystemforevaluatingthesingle-well recoverablereservesandtheresourcesofotherperiodsforeighttypesofunconventionalpetroleumincludingtightoiland gasandshaleoilandgas,providingastandardmethodologyforresourceevaluation;(9)torevealthe “orderlyaccumulation” ruleofconventionalandunconventionalpetroleum,whichpointsoutthatunconventionalpetroleumisassociatedwiththedirectionofhydrocarbonsupplyforconventionalpetroleum,thatconventionalpetroleummaybeassociated intheperipheralspacesofunconventionalpetroleum,thatoildetectionshouldturnfrom “outsidethesource” to “insidethe source,” andthatanewmodelofconventional unconventionalcodevelopmentshouldbeestablished;and(10)to recommendthatChinaincreaseitsreserves,raisetheproductionoftightoilandgas,andenhancethescaledevelopmentof shalegas,CBM,andoilshaleoil,aswellasthatitstrengtheninnovationrelatedtoshaleoilandhydrateexplorationand pushunconventionalpetroleumintotheroleofastrategicreplacementresource.
Nevertheless,unconventionalpetroleumisalsofacedwith10challenges:(1)thechallengeofthetraditionalcoarsegrainedsedimentology,whichcallsforthedevelopmentof fi ne-grainedsedimentologyfocusedonclasticrocksand carbonaterocks;(2)thechallengeofconventionalporereservoirs,whichcallforthedevelopmentofunconventional reservoirscontainingmainlymicro-tonanoscalepores;(3)thechallengeoftheconventionaltrapaccumulationconcept, whichcallsforthedevelopmentofunconventionalpetroleumfocusedontheconceptofcontinuouspetroleumaccumulation;(4)thechallengeofthetraditionalgeophysics,whichcallsforthedevelopmentoftechnicalevaluationmethods relatedtothesixaforementionedcharacteristics;(5)thechallengeofthetraditionalresourcereserveevaluation,whichcalls fortheestablishmentofatechnicalandeconomicrecoverablereservesystemandstandard;(6)thechallengeofthevertical welldrillingtechnique,whichcallsforthedevelopmentoflarge-scalehorizontalwellfracturingtechniques;(7)the challengeoftheextractionmode,whichcallsforthedevelopmentofplatform-basedfactoryproduction;(8)thechallenge ofthemanagementmode,whichcallsfortheestablishmentofafull-processlow-costmanagementmodel;(9)thechallengeofnontechnicalissues,whichcallforeffectivesupportfrompolicies,oilpricing,money,environmentalprotection, andfacilities;and(10)thechallengeofschooleducation,whichcallsforthecultivationofnew,unconventional,and innovativetalents.
Thesuccessfuldrillingofthe fi rstindustrialoilwellintheUnitedStatesin1859isgenerallyconsideredtobethe beginningofmodernpetroleumexplorationanddevelopment.In1917,theAmericanAssociationofPetroleumGeologists (AAPG)wasfoundedandbeganpublishingtheAAPGBulletin,whichestablishedpetroleumgeologyasanindependent discipline.In1934,E.H.McCollough(1934)formallyintroduced “traptheory,” whichbecamethecoreofconventional petroleumaccumulation.In1954,AmericanauthorA.I.Levorsonpublished “GeologyofPetroleum,” whichrepresented thepreludetosystematicandscientifictheoriesofpetroleumgeologyandboostedtherapiddevelopmentoftheworld’s petroleumindustry.
Researchonunconventionalpetroleumdatesbacktothe1930s,whenunconventionalpetroleumwasdefinedasopen reservoirsaccordingtotheclassi ficationofW.B.Wilson(1934).Sincethe1980s,unconventionalpetroleumresources suchasbasin-centeredgas(Law,2002),coalbedgas(AyersJr.,2002),shalegas(Nielson,1990),tightsandstonegas (Masters,1979),andshaleoil(Parker,1970)havegraduallybecomethekeyareasforincreasingreservesandproduction aswellasresearchhotspots.Researchonunconventionalpetroleumgeologyhasgainedsubstantialprogress,encompassingtheresourcemeaning,types,geologicalcharacteristics,resourceevaluationmethodology,anddevelopment techniquesofunconventionalpetroleum.In1995,SchmokerandGautierfromtheUnitedStatesGeologicalSurvey (USGS)proposedtheconceptof “continuouspetroleumaccumulation,” whichreferredtothoseoilorgasaccumulationsin tightsandstone,coalrock,andshalerockoflargepetroliferousbasinswithindistinctlydefinedtrap capboundariesthat existmoreorlessindependentlyofoil gas waterinterfaces.
In2009,inlightoftheprogressmadeinunconventionalpetroleumexplorationandresearchinChina,theauthors introducedtheideaofcontinuouspetroleumaccumulationandrevealed10characteristics.In2011and2013,hepublished the firstandsecondeditionsof “UnconventionalPetroleumGeology.” In2012,Zoupublished “UnconventionalPetroleum Geology” inElsevier.In2013,Dr.Zouandhiscolleaguespublishedanarticleentitled “Geologicalconcepts,characteristics,resourcepotentialandkeytechniquesofunconventionalhydrocarbon:onunconventionalpetroleumgeology” in PetroleumExplorationandDevelopment (4).Since2012,theauthorhasundertaken “TrainingCoursesontheTheoryand EvaluationTechniquesofUnconventionalPetroleumGeology,” organizedbythehumanresourcesdepartmentofChina NationalPetroleumCorporation,whereheintroducedthelatestexplorationandresearchoutputsinsideandoutsideof
China,pushingforwardtheunconventionalpetroleumofPetroChina.Since2011,theauthorhasalsocommunicatedonthe explorationandtheoreticalandtechnologicalprogressinunconventionalpetroleumaroundtheworldatBeijingUniversity, ChinaUniversityofPetroleum(Beijing,EastChina),SouthwestPetroleumUniversity,ChangjiangUniversity,andXi’an PetroleumUniversity.In2010and2011,Zouandhiscolleaguesofferedanoptionalpostgraduatecoursecalled “UnconventionalPetroleumGeology” atthepostgraduatedepartmentoftheResearchInstituteofPetroleumExplorationand Development.Acompulsorycourse, “UnconventionalPetroleumGeology,” hasbeenofferedtogeologypostgraduates since2012.
Theauthorsdefineunconventionalpetroleumgeologyasanewdisciplineofpetroleumgeologythatchie flyfocuseson thetypeofunconventionalpetroleum, fine-grainedsediments,micro-tonanoscalereservoirs,andtheformationmechanism,distribution,enrichment,outputregime,evaluationmethodology,coretechniques,development,andeconomic evaluationofpetroleum.Thecoreofunconventionalpetroleumgeologyis “whetherreservoirpetroleumaccumulates continuously.” Theevaluationofunconventionalpetroleumgeologyfocusesonthesourceproperties,lithology,physical properties,brittleness,petroleumpossibility,andstressanisotropy(sixcharacteristics)andtheirrelationshipswithone anothertoenablethedeterminationofwhethergeneration,storage,andproductionofpetroleumarepossible.Thegoalof explorationistolookforcontinuousorquasi-continuousdistributionboundariesand “sweetspots” ofpetroleumandto developlow-costextractiontechniquesandeconomicdevelopmentmodels.Regardingresearch,conventionalpetroleum geologyisremarkablydifferentfromunconventionalpetroleumgeology.Conventionalpetroleumgeologycentersaround “whethertrapsaccountforaccumulation” andtheevaluationfocusesonthe “source,reservoir,caprock,trap,transport,and preservation” (sixcharacteristics)andtheirrelationshipswithoneanother.Thegoalofexplorationistolocatepetroliferous traps.Developmentmainlyinvolvestheestablishmentofhigh,stableproduction.
Theobjectivesofunconventionalpetroleumgeologyaretouseunconventionalideastoexplorenewtheories,new methods,techniques,andmanagementmodesandtoresolvetherapidlygrowingtheoreticalandtechnologicalproblems andproductiondemandsofunconventionalpetroleumexplorationanddevelopment.Thedevelopmentofunconventional petroleumgeologyisintendednotonlytoresolvetheenergydemandforhumansocietybutalso,andmoreimportantly,to cultivateunconventionalthinking,providingtheunconventionalmethodsneededtoreformtheworldandunconventional talentsrequiredtodrivetheworld,andtoformanunconventionalphilosophy.
Theauthorshavepreparedandpublishedthisformof UnconventionalPetroleumGeology bymodifying UnconventionalPetroleumGeology (secondedition)toprovideatextbookforstudentsaswellasareferenceforresearchinstitutes andpetroleumcompanies.First,thelatestprogressrelatedtothetheories,techniques,andexplorationanddevelopmentof conventionalandunconventionalpetroleumaroundtheworldisdescribed.Thisdiscussionisbasedonthenationalmajor petroleumproject “Accumulationlaw,keytechniquesandobjectiveevaluationonpetroleumreservoirsinlithologic formations,” theNationalKeyFundamentalResearchandDevelopmentProgramfortightandshaleoil(the973Program) andtheauthors’ ownlatestresearchoutput.Then,thetheories,techniques,andmethodsrelatedtotheunconventional petroleumindustryinChinaaresystematicallyexplainedinordertoincreasethepopularityofthisindustry.
UnconventionalPetroleumGeology consistsof15chaptersinthreeparts.Part1, “EssentialsforUnconventional PetroleumGeology,” consistsoffourchapters: “Introduction,”“MeaningofUnconventionalPetroleumGeology,”“UnconventionalPetroleumReservoirs,” and “UnconventionalPetroleumAccumulationandEvaluation.” Part2, “UnconventionalPetroleumTechnology,” consistsoffourchapters: “UnconventionalPetroleumResourceEvaluationMethods,” “ExperimentalAnalysis,”“GeophysicalTechniques,” and “WellDrillingandCompletionTechniques.” Part3,entitled “MiscellaneousUnconventionalPetroleum,” consistsofsevenchapters: “TightOilandGas,”“ShaleOilandGas,” “CBM,”“HeavyOilandBitumen,”“OilShale,”“NaturalGasHydrate,” and “OtherUnconventionalPetroleum Resources.”
TheForewordwaswrittenbyZouCainengandZhangGuosheng.ThePreamblewaswrittenbyZouCaineng.Chapter 1, “Introduction,” waswrittenbyZouCaineng,ZhangGuosheng,TaoShizhen,YuanXuanjun,HuSuyun,LiJianzhong, LiXiaodi,YangTao,WangHongjun,YangZhi,LiXin,andLiangKun.Chapter2, “MeaningofUnconventionalPetroleumGeology,” waswrittenbyZouCaineng,TaoShizhen,YuanXuanjun,YangZhi,ZhangGuosheng,WuSongtao, GaoXiaohui,andPangZhenglian.Chapter3, “UnconventionalPetroleumReservoirs,” waswrittenbyZhuRukai,Yuan Xuanjun,ZouCaineng,WuSongtao,BaiBin,YangZhi,JiangYuqiang,andMaoZhiguo.Chapter4, “Unconventional PetroleumAccumulationandEvaluation,” waswrittenbyZouCaineng,HouLianhua,YangZhi,WangLan,YangFan, YangChun,andLuoXia.Chapter5, “ResourceAssessmentMethodsforUnconventionalPetroleum, ” waswrittenbyGuo Qiulin,XieHongbing,andChenNingsheng.Chapter6, “ExperimentalAnalysis,” waswrittenbyZhuRukai,LiuShaobo, LiuKeyu,WuSongtao,BaiBin,GongYanjie,MaXingzhi,andHuangXiu.Chapter7, “GeophysicalTechniques,” was writtenbyZhangYing,ZhouCancan,LiChaoliu,andLiXia.Chapter8, “WellDrillingandCompletionTechniques,” waswrittenbyZhangGuosheng,ZouCaineng,ZhangYing,LiangKun,andLiXin.Chapter9, “TightOilandGas,” was
writtenbyZouCaineng,BaiBin,ZhuRukai,HouLianhua,YangHua,DuJinhu,WuSongtao,YangZhi,WangLan, YangTao,JiaJinhua,ZhangXiangxiang,SuLing,andPangZhenglian.Chapter10, “ShaleOilandGas,” waswrittenby DongDazhong,ZouCaineng,YangZhi,HuangJinliang,WangShejiao,LiXinjing,WangYuman,LinSenhu,Cui Jingwei,andWangShufang.Chapter11, “CBM,” waswrittenbyLiuShaobo,SongYan,MaXingzhi,HongFeng,and JiangLin.Chapter12, “HeavyOilandBitumen,” waswrittenbyNiuJiayuandJiangLingzhi.Chapter13, “OilShale” was writtenbyWuXiaozhi,WangHongyan,LiuRenhe,andGuoWei.Chapter14, “NaturalGasHydrate,” waswrittenbyZou Caineng,YangZhi,andTaoShizhen.Chapter15, “OtherUnconventionalPetroleumResources,” whichcoverscarbonate fracture cavitypetroleum,volcanicreservoirpetroleum,andmetamorphicreservoirpetroleum,waswrittenbyHou Lianhua,ZouCaineng,ZhuRukai,WangZecheng,TaoXiaowan,ZhangGuangya,YangFan,WangZhaoming,LiWei, ZhuGuangyou,KuangLichun,andMengWeigong.Thisbookwas finalizedandmodifiedbyZouCaineng,TaoShizhen, ZhangGuosheng,Yangzhi,BaiBin,HouLianhua,ZhuRukai,YuanXuanjun,andDongDazhong.
WearegratefultoProf.LiDeshengoftheChineseAcademyofSciencesandProf.AmosNurofStanfordUniversity forwritingprefaceforthisbook.Wearealsothankfultotheleaders,academics,andexpertsfromtheheadoffi ceofChina NationalPetroleumCorporation,RIPED,andtherelatedoilandgas fieldcompaniesandpetroleuminstitutionsfortheir kindsupportandassistance,aswellastoeditorSunYayunofGeologicalPublishingHouseforhercarefulwork.We expectthatkindcommentsandopinionsfromreadersregardinganymistakeorincorrectnessinthisbookwillbecorrected inournextedition.Thankyou.
Authors
Preamble
UNCONVENTIONALTHINKING
Conventionalpeoplemusthaveunconventionalthinking.Petroleumwillneverbeexhaustedbeforepeoples’ ideasare. Mistakenunderstandingistheforbiddenzoneofexploration.Petroleumexistswhereverwecanimagine.Petroleumis liberatedwhereverthehumanmindisliberated.Unconventionalpetroleumisfarbeyondconventionalideasandtechniques.Conventionalthinkingshouldbebrokentoseekunconventionalthinking.Evenconventionalpetroleumcallsfor unconventionalmethods.Oilisfoundbyconstantlyupdatingtheoildetectiontheories,techniques,andthinking;by breakingthroughthetraditionalknowledge,techniques,andmethods;andbycontinuouslyincreasingthemaximum hydrocarbongeneratingtemperature,decreasingtheminimumreservoirporosity,andincreasingthemaximumpetroleum depth.Oilcanbefoundbydevelopingoldzones,openingnewzones,andbreakingforbiddenzones.Petroleumcanbe foundbysearchingintherightdirectionandwiththerightmethod.Thedirectiondetermineswhetheranygivenpetroleum searchwillbesuccessful,whereasthemethodologydeterminestheamountofpetroleumfound,tolookthroughtheearth withwisdomandtominimizetheriskswithtechniques.Geologistsidentifywherepetroleumislocated,andexplorers pumpoutthepetroleum.Researchandexplorationnevercease.Discoveryisanabsoluteprinciple.Productionisanabsolutegoal.Tolookforpetroleumistolookforrulesandlargescales.Petroleumisfoundbyworkingrelentlesslyand nevergivingup.Findingpetroleumisbothatechniqueandanart.
THREEENERGYTRANSITIONS
Water,food,andenergyarethethreeelementsthatareindispensablefortheexistenceofhumanbeings.Energyislikethe powerthatdrivestheearthhumansforward,andpetroleumislikethesensitivenervesoftheearthlings.Theenergyuseof mankindhasundergonethreemajortransitionsfrom firewoodtocoal,fromcoaltopetroleum,andfrompetroleumto renewableenergy.Theperformanceofenergyextractionandtheefficiencyofenergyutilizationwillbecomethethemefor energytechnologicalinnovation.Withthecontinuousincreaseintheenergydemandoftheworldeconomyandsociety, thehigh-leveloperationofinternationaloilpricesandtheadventofalow-carbonsociety,thethirdtransitionfromconventionalpetroleumtonewenergyisboundtobecomeaninevitabletrend.Withinaforeseeableperiodoftime,however, newenergywill findithardtoliveuptoitsmission.Coal,petroleum,andenergyfromotherfossilfuelswillstillcontribute around80%oftheworld’stotalenergy.Conventionalandunconventionalpetroleumwillstillbetheprimaryenergy sources.Conventionalpetroleumresourceswillbechallengedbyunconventionalcounterparts,whicharedevelopinginto newconventionalresources.
THREE-HUNDRED-YEARLIFEOFPETROLEUMINDUSTRY
Threestageswillcharacterizethehistoryofthepetroleumindustry:conventionalpetroleum,conventionalandunconventionalpetroleumcodevelopment,andunconventionalpetroleumresourceexploitation.Thesestageswillcomprisethe entirelifeexpectancyofthepetroleumindustry.Thelifeexpectancyoftheworld’spetroleumindustryisforecastedtobe ontheorderof300years,startingfrom1859,whenthemodernpetroleumindustrycameintobeing.Thetraptheory proposedbyE.H.McColloughin1934isanimportantmilestonefortheformationofthetheoryofconventionalpetroleum geologythathasguidedtheexplorationanddevelopmentofconventionalpetroleumresources.Theideaofcontinuous petroleumaccumulationproposedbyJ.W.Schmokerin1995marksthebeginningofthetheoryofunconventionalpetroleumthathasprovidedthescienti ficbasisfortheeffectivedevelopmentandutilizationofunconventionalpetroleum resources.Continuousinnovationsrelatedtooildetectiontheories,techniques,andmethodshavealreadyoverthrownthe peaktheoryproposedbyM.K.Hubbertin1956.Itispossiblethattheworld’spetroleumproductionpeakwilloccuruntil the2030sor2040s,andthelifeexpectancyoftheworldpetroleumindustrywillbelongerthan300years.
TENMISTAKESINTHETRADITIONALUNDERSTANDINGOFPETROLEUM
Thereare10mistakesinthetraditionalunderstandingofpetroleum:(1)thatsourcerockscanonlyserveaspetroleumgeneratingstrataratherthanasreservoirs,whereasbreakthroughshavebeenmadeinshalegas;(2)thattightreservoirs arenotabletoreachindustrialcapacity,whereasindustrialproductionhasbeenrealizedbytightoilandgasandshalegas reservoirs;(3)thatpetroleumaccumulationisdependentontraps,whereasunconventionalcontinuouspetroleum accumulateswithoutdistincttraps;(4)thatpetroleumcanonlyaccumulatebysecondarymigrationunderbuoyancy, whereasunconventionalpetroleumcanaccumulateinsideornearsourceswithoutbuoyancy;(5)thatoil,gas,andwaterare distributedwithgasatthetop,oilinthemiddle,andwateratthebottom,withidenticalboundaries,whereasunconventionalpetroleumreservoirsdonotdisplayidenticaloil gas waterinterfaces;(6)thatpetroleumaccumulateswith caprock,whereasunconventionalpetroleumresourcesthemselvescanserveascaprock;(7)thatadeadlineexistsforthe petroleumexplorationdepthandthatultra-deeppetroleumhasnoeconomicvalue,whereas6000 8000multra-deep petroleumhasbeendiscovered;(8)thatthereareforbiddenzonesforpetroleumexploration,whereasoilandgas breakthroughshavebeenachievedinvolcanic,metamorphic,andshalereservoirs;(9)thatnegativestructuresinbasinor slopecenterschie flyreservewaterandhostlittleoilorgas,whereasscaleoilandgashavebeendiscoveredinnegative tectonicunits;and(10)thatpetroleumaccumulationindexesarerigidlyrestrictedbyupperandlowerlimits,whereasno suchrigidupperandlowerlimitsexistfortheformationandaccumulationofunconventionalpetroleum.Onlybybreaking throughthesemisunderstandingscanwe fi ndnewoilzones.
SIXNEWTRENDSFORRESEARCHINPETROLEUMGEOLOGY
Asthepetroleumindustrydevelops,fundamentalresearchinpetroleumgeologyhasdisplayednewtrends:(1)hydrocarbon generationevaluationisexpandingfromfocusingonthepeakperiodtotheentireprocessofhydrocarbongeneration;(2) reservoirtargetresearchisexpandingfromdiscoveringmicrometerporethroatstomillimeterporethroatsandfromhighqualityreservoirstonanoscalepore throatreservoirs;(3)geneticresearchisextendingfromconduit fl owaccumulation forreservoirshavingcarbonatefracturesandcavitiesandseepage fl owaccumulationformicro-tomillimeter-porereservoirstotheretentionreservingofnanoscalepore throatreservoirsundertightconditions;(4)petroleummigration dynamicsresearchisexpandingfrombuoyancydrivingtomultitypedynamicssuchasdifferentialdrivinganddiffusion; (5)petroleumaccumulationresearchisexpandingfromfocusingoncontinuousorsubcontinuouslargetrappetroleum zonesormeasurestorevealingtheorderlyspatialparagenesisamongdifferenttypesofconventionalandunconventional petroleumresources;and(6)resourcedistributionresearchischangingfromgeologicresourceevaluationtothespatial predictionoftechnicallyandeconomicallyrecoverableresources.
CHARACTERISTICSOFTHEPETROLEUMTECHNOLOGYREVOLUTION
Thepetroleumindustryismovingfromconventionalpetroleumtounconventionalpetroleum,triggeringamajorpetroleum technologyrevolutioninwhichtheminimumreservoirphysicalpropertiesarecontinuallydecreasingandthemaximum petroleumaccumulationdepthandtheultimatepetroleumrecoveryratioareconstantlyincreasing.Thepetroleumtechnologyrevolutionexhibitsthreeremarkablecharacteristics:overwhelmingtheories,technicalbreakthroughs,andindustrial production.Moreexactly,thetransitionfromlookingfortrapstosearchingforlargereservoirsexceedstheexploration scopeofthetraditionaltrapaccumulationtheory;thetransitionfromconventionalverticalwellexploitationtolarge-scale horizontalwellfracturingindicatesthatexploitationisnotlimitedtobeingperformedviathetraditionalverticalwell extractionmethod;thetransitionfromconventionalsingle-wellextractiontoplatform-basedmultiwellfactoryproduction doesnotfollowtheone-site,one-wellpattern.Thenewtechnologyrevolutionispilotingtheindustrialproductionof unconventionalpetroleumandadvancingthetheoriesandtechnologiesoftheworld’spetroleumindustry.
RESULTSOFTHEPETROLEUMTECHNOLOGYREVOLUTION
Thehistoryofthepetroleumindustryisahistoryoftechnologicaldevelopment.Thecontinuousinnovationinthetheories andtechnologiesofpetroleumgeologyprovidesinexhaustiblepowerfortheeconomicandsocialsustainabilityofthe world.Thetransformationfromconventionaltounconventionalpetroleumhasgeneratedtwogeologicaltheories(thetrap accumulationtheoryforconventionalpetroleumandthecontinuousaccumulationtheoryforunconventionalpetroleum) andfourcoretechnologies(verticalwelldrillingforconventionalpetroleum,seismicpredictionforconventional petroleum,large-scalehorizontalwellfracturingforunconventionalpetroleum,andnanotechnologyandgasdisplacement
forincreasingpetroleumrecovery).Thesetheoriesandtechnologieshavepushedthepetroleumindustryforward.In2013, theglobalpetroleumproductionexceeded70 108 toilequivalent.Technologydrivestheeffectiveutilizationof petroleumresources,whichinturnsatis fiesthepetroleumdemandofhumansociety.
TYPESOFPETROLEUMRESOURCES
Basedontraditionaltraps,petroleumresourcescanbeclassi fiedastectonic,lithostratigraphic,andcompositepetroleum reservoirs.Basedongeological,technical,andeconomicfactors,petroleumresourcescanbegroupedintoconventional andunconventionaltypesthatareincasualandspatialassociation.Conventionalpetroleumresourceschie flyinclude singletectonic,clusteredlithologic,andstratigraphicpetroleumreservoirs.Unconventionalpetroleumresourceschie fly includecontinuousoilsand,carbonate,andvolcanicreservoirfracture cavitypetroleum;continuoustightoilandgas, shaleoilandgas,andCBM.Theglobalpetroleumindustryisexpandingquicklyfromlandtodeep-waterzones,from shallowandmiddlelayerstodeepandultra-deeplayers,andfromconventionaltounconventionalresources.Ultra-deep (>3000m)marinezones,ultra-deep(>6000m)landmeasures,andpore(<1000nm)-ultra-tighttypeswillbecomethe threenewstrategic fieldsforpetroleumindustrydevelopment.
MEANINGOFUNCONVENTIONALANDCONVENTIONALPETROLEUM
Unconventionalpetroleumisdefinedascontinuousorsubcontinuousaccumulationsofpetroleumresourcesforwhich naturalindustrialproductionisnotachievablebytraditionaltechniquesandeconomicextractionisnotpossibleunlessnew techniquesareusedtoimprovethereservoirpermeabilityor fluidviscosity.Unconventionalpetroleumischaracterizedby twokeyindicators:(1)theextensive,continuousdistributionofpetroleumwithnodistincttrapboundariesand(2)no stablenaturalindustrialproductionandindistinctDarcy flow.Geologically,unconventionalpetroleumischaracterizedby source reservoirparagenesis,extensiveoccurrenceinbasinslopeandcenters,indistincttrapboundariesandhydrodynamics,andextractionchie flybylarge-scalehorizontalwellfracturing,platform-basedfactoryproduction,and/ornanoand gasdisplacementtoincreaserecovery.Bytype,unconventionalpetroleumincludesshaleoilandgas,CBM,tightoiland gas,heavyoil,andbitumen.Ontheotherhand,conventionalpetroleumisdefinedbytrap-typepetroleumresourceswhose naturalindustrialproductionisachievablebyexistingtechniques.Geologically,conventionalpetroleumischaracterizedby favorablereservoirphysicalproperties,source reservoirseparation,distincttrapboundariesandhydrodynamics,identical oil gas waterinterfaces,typicaloccurrenceinpositivetectonicunitsineithersingleorclusteredform,andexploration andextractionnormallybytraditionaltechniquessuchasverticalwellorseismicmethods.Bytype,conventional petroleumincludestectonic,lithologic,andstratigraphicreservoirs.
DIFFERENCESBETWEENUNCONVENTIONALANDCONVENTIONALPETROLEUM
Unconventionalresourcesareoilandgasthatarelocatedinstrataandthat flownegligibly.Conventionalresourcesareoil andgasthatarelocatedintrapsandthatare fl owable.Inpetroliferousbasins,unconventionalpetroleumresourcesare commonlydistributed,whileconventionalpetroleumresourcesaccumulatedintrapsaretheenriched “sweetspots” inthem andhavelimiteddistributions.Theprimaryfactorsthatdifferentiatebetweenunconventionalpetroleumaccumulationand conventionalreservoirsarerelatedtowhetherthepetroleumiscontrolledbytrapsandwhethernaturalindustrial productionisachievablebysinglewells.Unconventionalpetroleumisstudiedtoanswerwhetherpetroleumiscontainedin reservoirs,exploredtoidentify “sweetspots” andestablishtheboundariesofcontinuousorsubcontinuouspetroleum zones,developedtoseekinitialhighproductionandlong-termcumulativeproduction,andthekeyworkcontentisto prepareamaturesetofoutputs:aplanelayoutofthesourcerockthickness,aplanelayoutofthereservoirthickness,a structuraldiagramofthereservoirtop,andanevaluationtabledescribingthecorezones(threediagramsandonetable).As techniquesadvance,itwillbepossibleforunconventionalresourcestodevelopintoconventionalresourcesovertime. Conventionalpetroleumstudyistoanswerwhethertrapsareabletoformaccumulations,conventionalpetroleum explorationistolocatetheboundariesofpetroliferoustraps,conventionalpetroleumdevelopmentistoseeklong-termhigh andstableproduction,andthisworkistoprepareplanelayoutsoftraps,aswellascross-sectionsofreservoirsandtablesof trapelements(twodiagramsandonetable).
UNCONVENTIONALTOCONVENTIONALPETROLEUMRESOURCERATIO:80:20
Generally,unconventionalpetroleumresourcesmakeup80%ofallpetroleumresources,whileconventionalpetroleum makesuptheadditional20%.Theamountofrecoverableunconventionaloilresourcesintheworldisapproximately
6200 108 t,whichisroughlythesameasforconventionalpetroleum.Theamountofrecoverableunconventionalnatural gasintheworldisapproximately4000 1012 m3,whichrepresentseighttimesthatoftheconventionalcounterpart.The amountofrecoverableunconventionaloilinChinaisapproximately240 108 t,whichisroughlythesameasthatofthe conventionalcounterparts.TheamountofrecoverableunconventionalnaturalgasinChinaisapproximately 100 1012 m3,whichrepresents fi vetimesthatoftheconventionalcounterparts.Greatbreakthroughshavebeenmadein unconventionalpetroleum.Oilsandstoneoil,heavyoil,tightgas,andCBMhavebecomethekeyareasforunconventional petroleumdevelopment.Shalegasandtightoilhavebecomethehotspotsforunconventionalnaturalgasandoildevelopment,respectively.Unconventionalpetroleumhasbecomeanimportantpartoftheworld’spetroleumsupply.In2013, unconventionaloilandnaturalgasproductionalreadycontributed6%andmorethan17%,respectively,oftheworld’stotal oilandtotalnaturalgasproduction.Asforecasted,unconventionalpetroleumproductionwillcontributeover20%ofthe world’stotaloilandgasproduction.
ORDERLYACCUMULATIONOFCONVENTIONALANDUNCONVENTIONAL PETROLEUM
Theorderlyaccumulationofconventionalandunconventionalpetroleumisthecontinuouschargingofconventionaland unconventionalpetroleumovertimeandspaceinpetroleum-richbasinsorsags,wheretheyaregeneticallydifferentfrom, relianton,andcloselyparagenicwitheachother,formingauniformpetroleumaccumulationsystem.Thissystemreveals theorderlyaccumulationlawofdifferenttypesofpetroleumresources,suggestingthatconventionalandunconventional petroleumresourcesinpetroleum-richbasinsandsagsshouldbestudied,deployed,andexploredsynchronouslyandthat multiwellplatform-basedsynchronousextractionmaybeappliedtoplan,build,anddevelopdifferenttypesofpetroleum withthepurposeofincreasingexplorationanddevelopmentandimprovingtheresourceexploitationeffi ciencyand economicbenefits.Throughthislaw,itispossibletoinvestigatethespatiallocationofdifferenttypesofpetroleum. Generally,thediscoveryofconventionalpetroleumisanindicationofthepossibleparagenesisofunconventional petroleuminthehydrocarbonsupplydirection,andthediscoveryofunconventionalpetroleumindicatesanassociation withconventionalpetroleumintheperipheralspaces.Horizontally,conventionaltectonicreservoirsandlithostratigraphic reservoirsaregenerallyhostedonbasinmarginsandslopes,whileunconventionaltightoilandgasandshaleoilandgas accumulateinsagsanddepocenters.Longitudinally,fromshallowtodeeplevels,far-sourceconventionalreservoirs,nearsourcetightpetroleum,andinside-sourceshaleoilandgasaredistributed.Oildetectionguidelineshavevariedoverthe pastyears.Generally,intheearlytomiddlephase,sourcecontroltheorywasappliedtosearchforlargetectonicreservoirs, andcompoundpetroleumaccumulationzoneorlargepetroleumzonetheorywasappliedtolookfortectonicandlithostratigraphicreservoirclusters.Inthemiddletolatephase,moreattentionhasbeenpaidtounconventionalpetroleum resources,andthecontinuouspetroleumaccumulationpropositionhasbeenappliedtosearchfornear-sourcetightoiland gasandinside-sourceshaleoilandgas.However,thereorganizationthatisobservedinorderlyconventional unconventionalpetroleumsystemsdoesnotfollowthetraditionaloildetectionguidelines,requiringthatoilandgas detectiongeologicaltheoryadvancefromenablingsearchesforpoints,zones,orplanestoallowingsearchesformasses. Thisobservationalsodemandsthatthe “richbeforepoor” guidelinesthatlookforconventionalresourcesbeforeunconventionalresourcesbediscarded.Conventionalandunconventionalpetroleumcantherebybeexploredanddeveloped totheutmost.
NANOPORESYSTEMRESERVOIRS
Generally,unconventionaltightreservoirsarechie flynanoscalepore throatsystems,withmillimetertomicrometerpores locallydeveloped.Theporediameterrangesfrom50to500nminnanoscalepore throatsystemreservoirs,from5to 200nmforshalegasreservoirs,from30to400nmforshaleoilreservoirs,from40to500nmfortightlimestoneoil reservoirs,from50to900nmfortightsandstoneoilreservoirs,andfrom40to700nmfortightsandstonegasreservoirs. Betweenthe fluidsandthesurroundingmediainthesenanoscaleporethroats,thereareconsiderableviscousandmolecular forces.Petroleumisadsorbedonthesurfacesofmineralsorkerogensinanadsorbedstateorinsidesolidorganismsina diffusedstate,wheremigrationiscontrolledbypetroleumslippingandsurfaceinteractions,resultingindetentionthatis notsubjecttoDarcy’slaw.Differentialpressureanddiffusionaretheprincipaldriversofpetroleummigrationand accumulation.Poreconnectivitycangenerallybeusedtorepresentthe flowcapacity.Nanoscalepore throatsystems, whichaddtothereservoirspacesand fl owcapacityofpetroleumintightreservoirs,arethedecidingfactorsinthelongtermandcontinuousstableproductionofunconventionalpetroleum.
ARTIFICIALPETROLEUMRESERVOIRS
Conventionalreservoirs,alsocalled “trapreservoirs,” arenaturalpetroleumreservoirswithdistincttrapboundaries, identicaloil gas waterinterfaces,andnaturalpermeabilities.Thesereservoirscanproduceindustrialpetroleumgenerally withoutmanualfracturingorotherreforms.Unconventionalresources,whichhavenodistincttrapboundariesornatural industrialproductionanddemand “artificialpermeability,” canbecalled “artifi cialreservoirs.” Insuchreservoirs,verticalwellnetworkfracturingorhorizontal-wellvolumetricfracturingisnecessarytoformboreholelengthasthevolumetric unitsandartificialfracturingnetworkasthe flowpathwaysunderground.
Tightoilandgasandshaleoilandgasaretypicalexamplesofthese “artificialreservoirs,” fromwhichitisdiffi cultto obtainhighproduction,stableproduction,andenergyreplenishment.Currently,themostcommonpracticeinsideand outsideofChinaismultiwellplatform-basedfactoryextraction.Inthisextractionmethod,anumberofsimilarwellsare implementedintheformofawellfactoryplatform,constitutingatransformationfromthe “onewell,onereservoir” conceptinconventionalpetroleumextractiontothe “manywells,onereservoir” methodinunconventionalpetroleum extraction,whichseekstomaximizethestimulatedreservoirvolume.Refracturingcanalsobeappliedtoproduce “arti ficial permeability” againinoldreservoirs,therebyallowingcontinuedacquisitionattheproductioncapacity. “Arti ficialreservoirs” areexploitedbycontinuouswelldrillingtoincreasetheirproductioninitially,blockreplacementtoattainlongtermstableproduction,andwaterorgasinjectiontoprovide “artificialenergy.”
FINDINGOILNEARSOURCES
Sincetheexplorationphaseandpetroleumresourcetypediffer,somusttheoildetectionguidelinesandtheoretical framework.Generally,intheearlytomiddlephase,whichfocusedonconventionalresources,effortswereconcentratedon lookingforoiloutsidesourcesfromtrapsbytargetingtectonictrapreservoirsandlithostratigraphicreservoirgroups.Inthe middletolatephase,whichfocusedonunconventionalresources,effortswereconcentratedonsearchingfornear-source petroleumorinside-sourceshaleoilandgasbytheideaofsearchingoilnearsourcesfrommeasures,targeting.Thisphase furtherstheoildetectionguidelinesfromlookingforoiloutsidesourcesfromsingletrapstosearchingforoilnearsources fromcontinuousmeasures.
“Lookingforoilnearsources” istocomeintoorapproachtheoil-generatingmeasuresandlookforshaleoilandgas detainedinsidesources,near-sourcetightoilandgas,immatureoilshaleoilandCBM,etc.,whichisarevolutionfromthe traditionalguidelineoflookingfortrapreservoirsaroundsourcerocks,andthetraditionalmethodoflookingforoutsidesourceoilthathasexperiencedsecondarymigrationandtrappetroleumaccumulation.Lookingforoilinsidesourcesfrom measureshasledtochangesintheresearchguidelines,technicalmethods,anddevelopmentmodesofpetroleum exploration.Thetransitionsfromoutsidesourcesfromtrapstoinsidesourcesfrommeasuresandfrompetroleumreservoirs topetroleumformationsareinevitableresultsofpetroleumexplorationchangingfromemployingconventionalguidelines tousingunconventionalones.
TENSIGNIFICANTCHARACTERISTICSOFCONTINUOUSPETROLEUM ACCUMULATION
Continuouspetroleumaccumulation,thetypicaltypeofunconventionalpetroleumaccumulation,issignificantlydifferent fromconventionaltrapaccumulation.Ithas10characteristicsandtwokeysigns.The10characteristicsare(1)distributionin base/slopecentersandextensive, “continuous” distributionswithlocalenrichment;(2)developmentoflarge-scalenanopore systemreservoirs;(3)source reservoirparagenesis,continuousgenerationandaccumulation;(4)nonclosedtrapswithno distinctboundaries;(5)initialmigrationorshort-distancesecondarymigration;(6)accumulationchie flybypressuredifferenceanddiffusion,withbuoyanceplayingalimitedrole;(7)chie flynon-Darcy flow;(8)poor fluiddifferentiation,no identical fluidboundariesorpressuresystem,significantsaturationdifference,andlikelinessofthecoexistenceofoil,gas, andwater;(9)lowresourceabundance,withreservoirscalculatedbywell-controlledblocks;and(10)specialextraction processessuchastheuseofhorizontalwellsorotherselectivetechniques.Thetwokeysignsare(1)extensivereservoirs commonlycontainpetroleumand(2)buoyancyisnotthemaindynamicfactorforaccumulatingpetroleum.
PETROLEUMACCUMULATIONINSHALESYSTEMS
Basedontheirsource reservoirrelationships,petroleumdistributionscanbecategorizedassource reservoirseparated, source reservoircontacted,andsource reservoirintegrated.Unconventionaltrappetroleumistypicallysource reservoir
separated;unconventionaltightoilandgasismainlysource reservoircontacted;andshaleoilandgasandCBMare source reservoirintegrated.Petroleumexplorationhasprogressedfromsearchingforoilbasedontheappearancetodoing sobasedonthegeneticfactors,andfromfar-sourcetonear-sourceandinside-sourceshalesystems.Theshaleoilandgas andtightoilandgasinsideshalesystems,whichhavebecomethekeymeasuresanddirectionsforoildetection,canbe deployedasasetoftargetmeasuresduringexplorationanddevelopment.Petroleuminshalesystemshighlightspetroleum accumulationinsidesourcesorinreservoirswherethesourceandreservoirarecloselycontacted.Bytype,petroleumin shalesystemsincludesinside-sourceshaleoilandshalegasandtightoilandtightgasindirectcontactwiththesource rocks.Featuringsource reservoirparagenesisandcontinuousorsubcontinuousdistribution,thiskindofpetroleuminvolveslowgeologicrisksandisextractedbythescaleapplicationofhorizontalwellvolumetricfracturingorotherkey techniques.
SHALEOILPROSPECTS
Shaleoilreferstotheoilalreadygeneratedbutstilldetainedinthemicro-tonanoscalereservoirspacesoforganic-richmud shaleformations.Theoilhasbeendetainedinsituwithhardlyanymigration.Shaleisboththeoil-generatingrockandthe reservingrock.Unlikeitstightsandstoneandtightlimestonecounterpartsthathaveundergoneshort-distancemigration, shaleoilisgenerallydistributedextensivelyandcontinuouslyinbasincenters,inwhichtheshaleisentirelypetroliferous, providinghugestocksofresources.Noindustrialproductionofshaleoilhasbeenyieldedsofarfromthematrixporesof blackshalestrata.Continental,organic-richshaleisdevelopedinChina,wherenanoscalepore throatshalesystemsand fractureshaleoilhavebeendiscovered.Horizontalwellvolumetricfracturing, “natural,fracture” reformation,thecharring ofcoarseparticlestoform “arti ficialreservoirs,” gasinjectiontoproducehighgas oilratios,heatingandnanohydrocarbontechniquesarepossiblycoretechniquesforindustrializingshaleoil.ThetechnicalbreakthroughsandsuccessofNorthAmericawithrespecttomarineshalegasmakepossibleChina’sindustrializationofcontinentalshaleoil.
NATURALGASHYDRATEPROSPECTS
Inthe1980s,mancametorealizethathydrateswouldpossiblybecomeanewandimportantkindofenergyinthefuture, replacingoilandnaturalgas.Researchanddrillingexperimentsonhydratesareunderwayworldwide.Aconsensusis beingreacheduponthepossiblescaleeconomicextractionofhydratehostedinstabletemperature pressurezones.In 2001,Canadaprovedtheeconomicfeasibilityofhydrateextractionforthe firsttimeafterdrillinginthenortherntundra.In 2013,inthe firsthydrateextractiontest,Japanobtained11.9 104 m 3 ofnaturalgasfroma300mhydratebedbelowthe seabed,wheretheestimatedresourceamountwas1.1 1012 m3.Inthesameyear,Chinacompletednaturalgashydrate drillinginthenorthernslopeoftheSouthChinaSeaandobtaineddirectevidenceforhydratesfromtheloosesoftmud 10mbelowtheseabottomsurface.Inordertoovercomethetechnicalbarrierstohydrateextractionandtoindustrializethe productionofhigh-potentialhydrateresources,threetasksmustbecompleted.First,acommercialhydrateproductionscale mustbeachieved.InChina,thisprocesswillinvolve(1)evaluatingthesourcesupplyofstabletemperature pressure zoneswithafocusonhydratesontheslopesoftheSouthChinaSea,wheretheresearchbasisisfavorable;(2)identifying relativelycoarsereservoirfacieszones;and(3)determiningthedistributionrulesandeconomicresourcepotentialby drillingexperiments.Second,thecoretechniquesmustbeestablished,whichwillrequiredrillinganumberofgeologic surveyparametricwells,collectingthenecessarykeyparametersneededforevaluation,graduallyestablishinga comprehensiveevaluationmethodfor “sweetspots,” andovercomingkeytechnicalbottlenecksrestrainingthecommercial developmentofhydrates.Third,environmentalriskresearchmustbeperformed.Thedepressurizedextractioncurrently underexperimentationhasthepotentialtoinducegeologicdisasters,andthegreenhouseeffectcausedbymethanegasis morethan20timesthatcausedbycarbondioxide.Thenumerousenvironmentalproblemswilldirectlypreventthelargescaledevelopmentofhydrates.Commercialdevelopmentofhydratescouldconstituteanotherroundofrevolutioninnew energy,followingthe “shalegasrevolution.”
THREETECHNOLOGICALINNOVATIONSINUNCONVENTIONALPETROLEUM
Thestrategicbreakthroughsinunconventionalpetroleuminthenewcenturymainlyincludethreesymbolictechnological innovations:(1)aninnovationingeologictheory;namely,theknowledgeofthefactthatcontinuouspetroleumaccumulatesinnanoscalepore throatsystemreservoirs,breakingthetraditionalpropositionthattightreservoirsandshale stratahavepoorreservingabilities;infact,nanoscalepore throatreservoirspaceshavebeendiscovered;(2)aninnovation inthecoretechniqueinnovationoflarge-scalehorizontalwellfracturingtoformarti ficialpermeability;inthismethod,
long-intervalhorizontalwellvolumetricfracturingisappliedtoformthemaximalpetroleum flowspace,resolvingthe small-area fl owproblemexhibitedbynear-wellborepetroleumandchallengingthetraditionalverticalwelltechnique;and (3)aninnovationrelatedtothemodelofplatform-basedmultiwellfactoryextraction,namely,thattensofwellsworkon thesameblock,reducingthelandcoverageandcostandachievinghigherefficienciesthanarepossiblewiththetraditional one-blockone-wellmodel.Signi ficantbreakthroughsinthetraditionaltheory,techniques,andmodelshaveadvanced unconventionalpetroleumintoastrategicreplacementarea.
ADVANCESACHIEVEDFROMUNCONVENTIONALPETROLEUMBREAKTHROUGHS
Unconventionalpetroleumbreakthroughshavebroughtusthreeimportantadvances:(1)theknowledgethatpetroleum areashavethepotentialtoenableindustrialproductionin10 20yearsandthatkeepingfundamentaltheoryresearchand stabletechnologicalinputistheprerequisiteformakingunconventionalpetroleumbreakthroughs;(2)knowledgeofthe keytechniques,technicalinnovations,andlow-costindustrializationteststhatarefundamentalforindustrializingunconventionalpetroleum;and(3)theknowledgethathighprice,marketcompetition,policysupport,andcompleteground facilitieswillmakethelarge-scaleextractionofunconventionalpetroleumpossibleinaneconomic,effectivemanner.For example,theindustrialproductionoforganic-richshale,apossibleimportantreplacementforpetroleuminfuture,would bepossibleiflong-termpreparationsaremadeintermsofthenanoscalepore throatspaces,oilaccumulationamount, predictiontechniques,andextractionmethodsofblackshale.
EFFECTSOFUNCONVENTIONALPETROLEUMBREAKTHROUGHS
Unconventionalpetroleumbreakthroughshavehadthreesignificanteffects.First,theyextendedthelifeexpectancyofthe petroleumindustry,brokethetraditionalforbiddenzonesofresourcesandreservoirtheory,andincreasedthenumberof typesandtheamountsofresourcesextracted.Second,theytriggeredthepetroleumtechnologyrevolutionandspurredthe updatingoftheentiretheoreticalandtechnicalsystemofthepetroleumindustry.Third,theychangedtheworld’straditionalenergyspectrumtoproduceaconventionalpetroleumlandscapeintheEasternHemispherecenteredaroundthe MiddleEastandanunconventionalpetroleumlandscapeintheWesternHemispherecenteringonAmerica.IntheUnited States,energysecurityisachievedbyimplementingtheenergyindependencestrategypoweredbyunconventionalpetroleum,enablingstrategicreadjustmentandcreatingnewworldpowerhierarchiesintermsofpolitics,economy,and military.
FUTUREUNCONVENTIONALPETROLEUMTECHNIQUES
Inthefuture,keytechniquessuchashigh-resolutionseismics,large-scalehorizontalwellfracturing,gasreplacementto improverecovery,andnano-hydrocarbontechniquewillhavetobedeveloped.Nano-hydrocarbonwillpossiblybean importantdirectioninthefuture.Withtheadventofanewglobaltechnologyrevolution,cross-integrationofbiotechnology,informationtechnology,andnanotechnologywillbeessentialtoachievefurthertechnologicaldevelopments.The petroleumindustrywillenterananotechnologyera,bywhichkeytechniqueswillhavebeenproduced:(1)nano-CT reconstructed3Dreservoirmodelsand3Dseismic fl uoroscopy;(2)nano-hydrocarbon-displacingagentsthatmaximize theoilandgasrecovery;(3)nano-hydrocarbon-extractionrobotstoperformthekeypetroleumexplorationanddevelopmentprocesses;and(4)nanomaterialsthatwillbewidelyusedthroughoutthepetroleumindustrysystem.Nanotechnology,biotechnology,andinformationtechnologywillbecomethenewcoretechnologiesforthepetroleumindustry, bringingaboutaneraofsmartpetroleum.
UNCONVENTIONALPETROLEUMSITUATIONINCHINA
Theyear2010canbecalledthe “firstyearofunconventionalpetroleum,” markingthebeginningofChina’spetroleum industry.In2009,continuousaccumulationtheorywasdevelopedinChina.In2010,China’smarineshalewasdiscovered, andtightoilandgasbecameanewhighlightofunconventionalpetroleum.In2011,Chinaissueditsindustrystandardfor tightgas,signalingtheentryintoagoldentimeforChina’spetroleumindustry,inwhichconventionalandunconventional areequallyemphasized.Tightgasassociatedwithcoalmeasureshasbecomeanimportantareaforincreasingreservesand production.In2013,China’stightgasproductionwasalready340 108 m3,oraboutathirdofthenation’stotalnatural gasproduction.TightoilthatisassociatedwithlacustrinesourcerocksexhibitedgreatbreakthroughsintheChang-7oil layeroftheOrdosTriassicYanchangFormationandformeda(5 10) 108 tlargetightoilregionthere.ForCBM,two
groundproductionbaseshavebeensetup:oneinthesouthofQinshuiBasinandoneintheeasternmarginoftheOrdos Basin.In2013,China’sgroundCBMproductionwas30 108 m3.InSichuanBasin,aLowerPaleozoicmarineshalegas corezonewasdiscovered.In2010,verticalwellWei-201yieldedshalegaswitha1 104 m 3 dailyyieldfromtheSilurian LongmaxiFormationinSouthernSichuan.In2011,horizontalwellNing-201-H1yieldedshalegaswithadailyyieldof over15 104 m 3 fromtheSilurianLongmaxiFormation.FromJanuarytoAugust2014,themarineshalegasproduction inSichuanBasintotaledover10 108 m3.In2013,theannualoilshaleoilproductionbygrounddestructivedistillation was80 104 t.Naturalgashydrateandshalegasalsorecordedimportantprogressintheoreticalandtechnological research.
THREELEVELSOFCHINA’SUNCONVENTIONALPETROLEUMINTHEFUTURE
China’spetroleumexplorationwillexhibitthreepeaks:areserveincreasingpeakfocusingonconventionalpetroleum;a majordiscoverypeakforbothconventionalandunconventionalpetroleum;andatechnologicalinnovationpeakhighlightingunconventionalpetroleum.Unconventionalpetroleumresources,withfarhigherpotentialthantheirconventional counterparts,willplayanimportantstrategicroleinChina’spetroleumindustryinthefuture.Itisthereforeimportantto increasethereservesandproductionofconventionalpetroleumandbreakthroughtheunconventionalpetroleumareato securestrategicreplacement.China’sunconventionalpetroleumwilldevelopatthreelevels.First,theproductionscaleof tightreservoiroilandgaswillincrease,aswillthereservesandproduction.Second,theindustrializationofshalegas, CBM,andoilshaleoilwillbeenhanced,andlarge-scaleindustrial,economicalextractionwillberealizedwhileminimizingtheextractiontime.Third,greatereffortwillbeexertedinfundamentaltheoryresearchandtechnicalexplorationon shaleoilandhydratessothattheycanreplaceconventionalenergysources.
