Reservoir Characteristics And Comprehensive Evaluation Of Wumishan Formation In Jizhong Depression

Based on previous research,this paper makes use of data from field outcrops,cores,ordinary sheets,cast thin sections,scanning electron microscopy and geochemical tests to study the characteristics of rocks,reservoir spaces and reservoir physical properties,to identify types of reservoir diagenesis and to discuss the relationship between reservoir diagenesis and pore evolution in Wumishan formation in Jizhong depression.After analyzing four major controlling factors of the high quality reservoir,combing with the evolution of sedimentary structures in the study area,this paper establishes a high quality reservoir formation and evolution model.Based on the reservoir evaluation of single-well and connecting-well section,and guided by the model of the high quality reservoir formation and evolution,this paper superimposes multiple factors of the development of favorable reservoir to complete reservoir comprehensive evaluation.The results show that main rock types in Wumishan formation in the study area are microbial dolomites,grain dolomites,crystal dolomites and siliceous dolomites.Main reservoir spaces include algae frame pores,intergranular pores,intragranular solution pores,moldic pores and tectonics.The physical property of the reservoir is characterized by high porosity and high permeability,and it has the highest porosity and permeability in the area of Renqiu and Xiongxian.The diageneses in the study area mainly include cementation,dolomitization,silication,dissolution,and rejuvenation of crystals.In combination with diagenesis stages,this paper establishes the sequence between diagenesis and pore evolution.The main factors controlling high quality reservoir development include sedimentary facies,diagenesis,fractures and faults,and ancient landforms.Among them,algal facies and reef facies,dissolution diagenesis(especially epigenic karstification),fractures and faults,paleotopographies of karst highland and karst slope are favorable factors for high quality reservoir development.There are three types of reservoirs in the Wumishan formation in the study area.Type I reservoirs are mainly located near Xiongxian and Renqiu,type II reservoirs are mainly in the middle of the study area,and type III reservoirs are mainly developed in Baoding to Dingzhou and Xiongxian north to Daxing.