Sedimentaryfaciesisanimportantfactorinfluencingshalegasaccumulation.Itnotonlycontrollshydrocarbongeneration,butalsoaffectsreservoircharacteristicsanddistribution.ThispaperdiscussestheLowerSilurianLongmaxiFormationinthesouthoftheSichuanBasin.Outcrop,core,drillingandloggingdataidentifythesedimentaryfaciesoftheformationascontinentalshelffacies,whichispidedintotwosubfacies:aninnershelfandanoutershelfsubfacies.Thesetwosubfaciescanbefurtherpidedintosevenmicrofacies:muddysiltyshallowshelf,calcareoussiltyshallowshelf,muddylimyshallowshelf,stormflow,muddydeepshelf,siltymuddydeepshelfandcontourcurrentmicrofacies.Verticalandhorizontaldistributionofmicrofaciesestablishesasedimentationmodelofthecontinentalshelffacies.Combinedwithanalizationorcalculationofgeochemical,mineralogical,physicalandgas-bearingpropertiesofsamples,sedimentarymicrofaciesisevaluatedusingnineparameters:totalorganiccarboncontent,effectiveshalecontinuousthickness,vitrinitereflectance,kerogentype,mineralcomponents,porosity,permeability,watersaturationandgascontent.Theevaluationrevealedthatthemostfavorablefaciesforshalegasexplorationanddevelopmentarethemuddydeepshelfandpartofthesiltymuddydeepshelfmicrofacies,withTOCmorethan2%,siliceouscomponentover50%,claylessthan30%,porositymorethan3%,watersaturationlowerthan40%,gascontentgreaterthan2m3/t.Theseresultsprovideatheoreticalbasisfordeciston-makingonthemostpromisingareasforshalegasexplorationintheSichuanBasinandformarineshalegasexplorationanddevelopmentinSouthChina.
