Sedimentary Evolution And Reservoir Characteristics Of Shaximiao Formation,in Mabian-Muchuan Area In The South Of Sichuan Basin

China's onshore natural gas resources are abundant,among which tight clastic gas reservoirs occupy an important position.At present,natural gas production in tight sandstone gas reservoirs accounts for about one-fifth of China's total annual natural gas production.In terms of proven reserves and technological capabilities,tight sandstone gas reservoirs are the most unconventional natural gas fields in China with realistic significance for exploration and development.The Mabian-Maichuan Shaximiao Formation in southern Sichuan is a typical tight sandstone,but the current exploration level is low and the exploration is difficult,and sedimentary evolution and reservoirs are the key.Based on sedimentology,reservoir geology,diagenesis and related research results at home and abroad,this paper used sample experimental analysis,thin section and other experimental data,combined with previous research results on the petrological characteristics and reservoir properties of the study area.The pore type,pore structure characteristics,and diagenesis type work.The characteristics of sedimentary evolution and sedimentary facies of the Shaximiao Formation in the study area were systematically studied,and the reservoir characteristics and control factors of Shaximiao Formation in the study area were further studied.On the basis of previous studies,the Middle Jurassic Shaximiao Formation in the Mabian-Muchuan area has been divided into three subsections:outcrop rock color,rock structure,sedimentary structure,sedimentary sequence characteristics,combined with cross-section study and geochemical research.For an ultra-long-term cycle,it can be divided into 2 long-term cycles and 7 medium-term cycles.During the deposition of the Shaximiao Formation,the regional sedimentary environment was generally a river-lake depositional environment.According to the detailed description of the field profile,indoor thin film and geochemical analysis,it is believed that the depositional environment of the Shaximiao Formation in this area is river sedimentation,and the type is meandering river.The macroscopic analysis of the reservoir sediment source and sedimentation rate of the Shaximiao Formation sandstone was combined with the microscopic observations of reservoir petrological characteristics and physical characteristics to study the relationship between reservoir physical properties and diagenesis type and sedimentary characteristics.The Shaximiao Formation in the study area is mainly composed of tight sandstone reservoirs with low porosity and low permeability,reservoir space,and the control of diagenesis,sedimentation,and tectonic action on reservoir properties.