搜索
SPE114992DevelopmentofCoalbedMethaneinAustralia:UniqueApproachesandToolsY.HamandA.Kantzas,UniversityofCalgaryCopyright2008,SocietyofPetroleumEngineersThispaperwaspreparedforpresentationattheCIPC/SPEGasTechnologySymposium2008JointConferenceheldinCalgary,Alberta,Canada,16–19June2008.ThispaperwasselectedforpresentationbyanSPEprogramcommitteefollowingreviewofinformationcontainedinanabstractsubmittedbytheauthor(s).ContentsofthepaperhavenotbeenreviewedbytheSocietyofPetroleumEngineersandaresubjecttocorrectionbytheauthor(s).ThematerialdoesnotnecessarilyreflectanypositionoftheSocietyofPetroleumEngineers,itsofficers,ormembers.Electronicreproduction,distribution,orstorageofanypartofthispaperwithoutthewrittenconsentoftheSocietyofPetroleumEngineersisprohibited.Permissiontoreproduceinprintisrestrictedtoanabstractofnotmorethan300words;illustrationsmaynotbecopied.TheabstractmustcontainconspicuousacknowledgmentofSPEcopyright.ABSTRACTCoalbedMethane(CBM),alsoknownasCoalSeamGas(CSG)orCoalSeamMethane(CSM)inAustraliaisfastbecomingasignificantcontributortothecountry’senergyneeds.ThepotentialcoalseamsformethaneproductioninAustraliaarefoundincoalzonesthatareJurassictoPermianinagewithcoalranksrangingfromsub-bituminoustolowvolatilebituminouscoals.ManyAustraliancoalseamscontainhighvolumesofmethanegasupto25m3pertonne.AustraliabeganproducingCBMin1988butitwasnotuntil1996whenthecommercialCBMproductionstartedinthestateofQueensland.AustraliahastotalCBMreservesofabout300to500Tcf(8.6to14.3trillionm3).WiththetotalamountofCBMin-placereservesworldwideestimatedtobebetween3,500and95,000Tcf(100and272trillionm3),CBMisconsideredoneoftheworld’slargestsourcesoffossilfuel.IntheUnitedStates,thetotalCBMin-placereservesareestimatedat749Tcf(21.4trillionm3),andCBMnowrepresentsalmost10%ofitsdomesticnaturalgasproduction.CanadahasjustbegunproducinggasfromCBMreservoirsanditsestimatedin-placeCBMreservesareabout1,300Tcf(37trillionm3).InAustralia,asCBMisseenasacleanandpipeline-qualityenergy,itisrapidlydeveloping.AlongwiththelargeCBMresource,themaindriversforthismovearethecontinuouslyreducingcostofcoalseamgasproduction,andthedepletingconventionalenergyresources.AnumberofsophisticatedCBMreservoirsimulationandexploitationtoolshavebeendevelopedbytheUniversityofNewSouthWalesandCSIROtosimulatetheconventionalCBMproductionaswellastheCBMrecoveryusingmulti-componentgases.Inthefield,AustralialookstowardenhancingCBMrecoverybyinjectingnitrogenandorcarbondioxidetoincreaseCBMextraction.ThispaperwillfocusonhowAustraliaismaximizingitsCBMproduction.INTRODUCTIONCoalis“theblackrockthatburns”(LandandRice,1993).Itisdefinedasareadilycombustiblerockthatcontainsmorethan50%byweightandmorethan70%byvolumeofcarbonaceousmaterialincludinginherentmoistureformedbycompactionandinduration(hardeningofsediment)ofvariousalteredplantremains.Thetypeofplantmaterials,degreeofmetamorphism,andtherangeofimpuritycharacterizecoal(BatesandJackson,1980).Acoalseamisabedofcoal,andthenaturalgasormethaneproducedfromcoalseamsisreferredtoascoalbedmethane(CBM).CBMproductionbeganinitiallytokeepcoalminingsafefromexplosions.Ifthemethane-airmixturewasintherangeof5to15%,methanewouldbeexplosive(Cervik,1967).However,withtheglobaloilproductiondeclineandthecoalbedmethanebeingaclean-burningfuelcomparedtotheconventionalfossilfuels,ithasbecomeanimportantresourcethatcanassistinaddressingtheworld’sgrowingenergyneeds.InCanada,since2000,therehasbeenanincreaseinCBMexplorationduetoincreasingnaturalgasprices,increasednaturalgasdemandbothdomesticallyandinternationally,developmentofnewtechnologies,andthematurationoftheWesternCanadianSedimentaryBasin(Beaton,2007).ItisexpectedthatCBMwillcontributesignificantlytofuturenaturalgassupply.Currently,itiscontributingnearly10%oftheU.S.gasneeds.2SPE114992WHATISCOALBEDMETHANE?Coalbedmethane(CBM)isanaturalbyproductofthecoalificationprocess,whichconvertsorganicmatterlikewood,andpeattocoal.CBMconsistsmostlyofmethane(CH4)buttheremaybesomeminoramountsofcarbondioxide,nitrogen,watervapour,andheavierhydrocarbonslikepropane,andethane.CBMisconsidered“sweet”not“sour”asitdoesnotcontainhydrogensulphide(H2S)(AlbertaEnergy,2007).CBMisanunconventionalgasthatisdifferentfromnaturalgasfromaconventionalsandstonereservoirinthat,unlikepetroleumresources,itisbothgeneratedandstoredwithinthecoalbeds.Therefore,itisanattractiveresourcethatcanbeproducedfromcoal,whichisthemostabundantfuelintheworld.AccordingtotheWorldCoalInstitute(2006),coalreservesareavailableinalmosteverycountryworldwideproviding25%oftheglobalprimaryenergyneeds,withrecoverablereservesinaround70countries.Attheendof2006,therecoverablecoalreservesamountedtoaround998billiontons,whichisequaltoabout4,417billionbarrelsofoilequivalent,andatcurrentproductionlevels,theprovencoalreservesareestimatedtosustainproductionfor164years(WikipediaonCoal,2007).CBMisphysicallyadsorbedonthemolecularsurfaceofthecoalandstoredinmicropores.Althoughcoalporevolumeissmall(10%ofitsvolume),themicroporesofcoalhaveimmensecapacityformethanestorage.Coalcanbelikenedtoaspongeasitcanstoresixtimesthe