Integration of Core Data, Well Logs and Seismic Attributes for Identification of the Low Reservoir Quality Units with Unswept Gas in the Carbonate Rocks of the World＇s Largest Gas Field

TightzonesofthegasbearingKanganandDalanformationsoftheSouthParsgasfieldcontainaconsiderableamountofunsweptgasduetotheirlowporosity,lowpermeabilityandisolatedporetypes.Thecurrentstudy,integratescoredata,rockelasticpropertiesand3Dseismicattributestodelineatetightandlow-reservoir-qualityzonesoftheSouthParsgasfield.Inthefirststep,thedynamicreservoirgeomechanicalparameterswerecalculatedbasedonempiricalrelationshipsfromwelllogdata.Thelog-derivedelasticmoduliwerevalidatedwiththeavailablelaboratorymeasurementsofcoredata.CrossplotsbetweenestimatedporosityandelasticparametersbasedonYoung'smodulusindicatethatlowporosityzonecoincidewithhighvaluesofYoung'smodule.Theresultswerevalidatedwithpetrographicstudiesoftheavailablethinsections.Thecoresampleswithlowporosityandpermeabilityarecorrelatedwithstrongrockswithtightmatrixframeworksandhighelasticvalues.Subsequently,rockelasticpropertiesincludingYoung'smodulusandPoisson'sratioalongwithporositywereestimatedbyusingneuralnetworksfromacollectionof3Dpost-stackseismicattributes,suchasacousticimpedance(AI),instantaneousphaseofAIandapparentpolarity.Distinguishinglowreservoirqualityareasinpayzoneswithunsweptgasisthenfacilitatedbylocatinglowporosityandhighelasticmodulusvalues.Anhydritezonesareidentifiedandeliminatedasnon-payzonesduetotheircharacterizationofzeroporosityandhighYoungmodulusvalues.Themethodologydescribedhasapplicationsforunconventionalreservoirsmoregenerally,becauseitisabletodistinguishlowporosityandpermeabilityzonesthatarepotentiallyproductivefromthoseunprospectivezoneswithnegligiblereservoirquality.