Favorable Layer Optimization And Evaluation For Longmaxi Formation,Lower Silurian Shale In Southeast Upper-Yangtze

On the southeastern margin of the upper-Yangtze area is South China marine shale gas development in key areas,especially the Longmaxi formation shale thickness is big,wide distribution,high organic carbon conten,and shale gas exploration had greatly advanced.Paper based on the analysis of a large number of experimental tests,Systematic analysis of shale gas development geological conditions in study area,discussed the different microfacies segments shale gas-bearing features,optimized the exploration and development of shale favorable layer,combined with the parameters of the shale favorable layer to geological evaluation,mainly achieved the following understanding:On the southeastern margin of the upper-Yangtze of Longmaxi formation organic-rich shale thickness from deep shelf sedimentary center to the edge until the shallow shelf gradually thinning.The type of shale organic matter is maily?,followed by the?₁,high-quality gas-bearing shale layers with higher organic carbon content,high thermal evolution of features.Black shale with high brittle mineral conten;Various pore types,maily including intergranular pore,intragranular pore,organic matter pores and micro cracks;pores in the majority of mesopore,microporous content is also high,which the development of a large number of large contributions contrast surface by organic matter micropores..According to the study area sedimentary facies flag subfacies further divided into muddy shelf,sand and mud mixing shelf,and sandy shelf three microfacies,combined with the mineral composition and content of organic carbon in the Longmaxi shale is divided into 12 types of lithofacies.By analyzing different typical shale gas drilling shale sedimentary microfacies characteristics segment,recognizing the deep shelf muddy shelf shale segment and deep shelf sand mud mixed shelf shale segment of shale development conditions beneficial to shale gas generation and accumulation,and the brittle mineral content,have great potential for exploration and development.The study area Longmaxi formation shale gas-bearing high value area on the plane located in the area of Daozhen–Shizhu–Zhongxian,gradually decreased to the edge of sedimentary center.Vertically Longmaxi formation organic-rich shale gas-bearing with the depth of the show a good increase trend.Combined with shale sedimentary microfacies characteristics of the selection of two favorable areas of shale in the favorable segment,namely the muddy shelf shale segment and sand mud mixed shelf shale segment.According to the geological quality conditions for the development of shale gas,sedimentary facies and gas-bearing features,select evaluation parameters,establish the evaluation criteria of weight assignment,geological comprehensive evaluation of different shale segment in different sedimentary environments.Comprehensive parameters index considered,the deep shelf sedimentary center mud shelf shale layer is the most favorable segment,followed by the edge of muddy shelf shale segment,sand and mud mixed mass shelf of the deep shelf sedimentary is also have a certain value of exploration and development.