The Main Controlling Factors For The Development Of The Upper Sinian Dengying Formation Reservoirs In Southeastern Sichuan

The deep-ultra-deep carbonate reservoirs are widely distributed and have large thickness.The discovery of the Anyue gas field reveals the formation mechanism and development model of ultra-deep carbonate reservoirs in the Sinian Dengying Formation Exploration of marine carbonate reservoirs has important economic and scientific value.Reservoir characteristics of the Dengying Formation in southeast Sichuan basin is complicated because of the old age,great burial depth and multiple diagenetic transformation.Based on the theories of carbonate sedimentology,geochemistry,and reservoir geology,this paper expounds the Characteristics of reservoir development and distribution of Sinian Dengying Formation in the southeastern Sichuan Basin by means of outcrop and core observation,thin-film identification,pore permeability measurement,and 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 evolution of pores and reservoir distribution.Through the analysis of the pore permeability of the study area,we found that the 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.