挪威石油董事会油气储量分类标准和SPE的对比

NorwegianPetroleumDirectorate(NPD–2001)OneoftheprincipaltasksoftheNorwegianPetroleumDirectorate(NPD)istomaintainanoverviewofpetroleumresourcessothatauthoritiescanhavethebestpossiblebasisforplanningmeasurestoensurethattheyarewellmanaged,andtoforecastfutureproductionandactivity.TheNPD’sannualupdatingoftheresourceaccountforexpectedrecoverableresourcesfocusesonclassificationbymaturity.Thissystemwasdevelopedin1997.Basedonexperiencegainedinusingthesystemandincooperationwithseveraloilcompanies,theNPDdevelopedandpublisheditscurrentrevisedsystemin2001.ThecurrentsystembuildsontheSPE/WPC/AAPG2000classificationbutexpandsontheprojectmaturityaspect.ThemainprincipalintheNPDclassificationsystemisthatoriginallyrecoverableresourcesinafieldordiscoverymustbeclassifiedaccordingtotheirpositioninthedevelopmentchain,eitherfromadiscoverybeingmade,oranewopportunitytoincreaserecoverableresourcesinafieldbeingidentified,untilproductionoftheresourcesiscomplete.Thesystemisdesignedtoallowasinglefieldordiscoverybeingabletocontainresourcesindifferentprojectstatuscategories,i.e.resourcesatdifferentstagesofmaturityinthedevelopmentchain.Allresourcesmust,asfaraspossible,bereportedwithahighandalowestimateinadditiontothe“baseestimate”.Thisallowsanopportunitytodescribetheuncertaintyintheresourcequantitiesinboththeindividualfieldsandthefullresourceaccount(totalportfolio).Theresourcesaredividedintotendifferentprojectstatuscategories(Figure1).Figure1:NorwegianPetroleumDirectorateClassificationCategories0to7coverthediscovered,recoverableresources,Possiblefuturemeasurestoimprovetherecoveryfactorareplacedincategory7alongwithdiscoveriesthathavenotyetbeenevaluated.Categories6and9coverundiscoveredresources.The“F”labelidentifiesquantitieslinkedtotheinitialrecoveryprojectwhile“A”areadditionalquantitiesfromimprovedrecoveryprojects.Therearecaseswhere“A”canbenegative;forexample,oilrecoveryimprovementsmayinvolvegasconsumption.AllcompaniesoperatinginNorwaymustannuallysubmitresourceinformationaccordingtothisclassification.Moreover,themajorNorwegian-basedoilandgascompanieshaveadoptedthesameorsimilarsystemforinternalresourcemanagement.AcompletedescriptionoftheNPDclassificationcanbefoundontheirwebsiteat:(NPD2001)isbasedontheSPE/WPC/AAPG2000classification(figure2)withamodificationtoutilizeprojectstatuscategoriestodifferentiateprojectsbasedontheircommerciality,thatis,theirmaturitytowardsfullproducingstatus.Thesecategoriescanalsobeviewedasqualitativemeasuresofcommercialriskorchanceofcommerciality.Figure2:ComparisonofSPEandNPDClassificationsTheNPDclassificationisagoodexampleofamodifiedapplicationoftheSPE2000classification.Itadherestotheguidelinesprovided,inthatitisprojectstatusbased.Thismeansinprinciplethattheuncertaintyonthehorizontalaxisrelatestotheoutcomesofspecifiedrecoveryprojects,andthatthereisonelineforeachproject.WhiletheprojectstatuscategoriesfollowtheillustrativeexampleprovidedintheSPEguidelines(shownabove)toagreatextent,theyhavebeenadaptedtomatchtherequirementsoftheNorwegianlegalandregulatorysystem.Itfollowsfromtheprojectstatusapproachthattheremaybeseveralprojectsrecoveringoilandgasfromthesameaccumulation,andthesemaybeindifferentstagesofmaturity,andthusindifferentcategories.TheNPDhasfoundittobeconvenienttodistinguishbetweenthefirst(F)projectandadditional(A)projects.Probabilisticquantificationisprovidedfor,followingtheSPEscheme,butalsoallowingotherlegacyfractiletobeused,inordernottounnecessarilyburdencompanieswhowereusingP80andP20whentheexistingclassificationwasintroduced.Withtime,P90,bestestimatesandP10haveprevailedandtheP80andP20fractilesarenolongerusedasstandards.TheNPDsubstitutestheterm“baseestimate”for“bestestimate”.Itreflectsthecurrentunderstandingoftheextension,characteristicsandrecoveryfactorofthereservoir.Thebaseestimatecanbecalculateddeterministicallyorstochastically.Ifthebaseestimateiscalculatedbyastochasticmethod,itshouldcorrespondtothemeanvalue(notthemedian/P50).AstheNPDclassificationisdevelopedfortheresourcemanagementneedsoftheNorwegianGovernmentandthebusinessprocessmanagementneedsoftheNorwegiancompanies,emphasishasbeenmoreonreflectingrelevantquantitiesthatcomparableones.Thelatterisofcourseoftheessenceinfinancialreporting.Asaconsequence,theNPDclassificationislackinginprecisionwhenitcomestotechnicalandeconomiccriteriadefiningreserves.TheconceptofprovedreservesaccordingtodeterministiccriteriaisnotrecognizedasweknowitfromtheSECorSPEdefinitions.P90reservesarehoweverbothareasonableandsimple,well-definedsubstitute,rememberingthatfuture,uncommittedprojectsarenotallowedtocontributetothe2Pnor3Preserves.WhilethetermsProved,ProbableandPossiblearenotutilized,thedefinitionsoflow/1P,base/2P,andhigh/3Pestimatedquantitiesallowderivationoftheseentitiesifrequired(notwithstandingthatthebaseisthemeanandnotP50).TheNPDdefinesadiscoveryasonepetroleumdeposit,orseveralpetroleumdepositscollectively,whichhavebeendiscoveredinthesamewildcatwell,inwhichthroughte