Research On Reservoir Characteristics Of The Sinian Dengying Formation In Northern Sichuan Basin

Deep and ultra-deep carbonate reservoir is becoming the hotspot of oil and gas exploration,and the discovery of Anyue oversize gas field reveals the great exploration potential of the Dengying Formation.Reservoir characteristics of the Dengying Formation in northern Sichuan basin is complicated because of the old age,great burial depth and multiple diagenetic transformation.Based on the theories of carbonate sedimentology and reservoir geology,this paper systematically studies the reservoir characteristics of the Dengying Formation in northern Sichuan basin by means of outcrop and core observation,thin section identification,porosity and permeability measurement,geochemical analysis,etc.The sedimentary facies of the Dengying Formation in the study area is mainly carbonate edge platform,including algal mound,grain beach,dolomitic flat and lagoon subfacies.The main lithology of the reservoir in the study area is thrombolite dolomite,stromatolithic dolomite and grain dolomite,and the reservoir space is mainly secondary dissolved pores.The Dengying Formation in the study area has experienced complicated diagenesis;the constructive diagenesis includes penecontemporaneous dolomitization,dissolution and late tectonic fracturing;the destructive diagenesis includes cementation,compaction and silicification.Cementation and dissolution are the main diagenesis affecting the porosity evolution.Reservoir development in the study area is controlled by sedimentary facies and diagenesis.Algal mound and grain beach in platform edge are the favorable subfacies for reservoir development,and penecontemporaneous fresh water dissolution controlled by sequence is the key diagenesis to the development of reservoir space.