Reservoir Properties And Favorable Area Optimization For Longmaxi Formation,lower Silurian Shale In The Southeast Edge Of Sichuan Basin

The Sichuan basin and its surrounding area is one of the key exploration and development zones of China's marine shale gas,where the Longmaxi Formation of Lower Silurian has good geological conditions for shale gas' s development.Due to strong complex regional structure,later reformation and complex hydrocarbon content changing,objective understanding of its resource potential is the hotspot in theory research and exploration.This paper studys geological background of shale's development,reservoir properties and content of shale gas,which established the gas content prediction model and selected favorable area optimization with a multi-factor method.And obtained the following conclusions:The Longmaxi formation shale are formed in the deep continental shelf and shallow continental shelf environment,which are semi-closed.From the deep continental shelf to the shallow continental shelf environment,shale thickness becomes smaller and the abundance of organic matter decreased gradually.The main pore types of shale are organic pore,intergranular pore,intergranular pore,intergranular pore and dissolution pore with the middle hole,micro hole as the main.The organic matter content is the main controlling factor of nano pore volume and the surface area,with a good positive correlation.Shale reservoir physical property in deep continental shelf is better than that of the shallow continental shelf,which has low porosity and low permeability.The porosity and permeability is weakly positive correlated to the content of minerals such as quartz and is weakly negative correlated to the carbonate minerals,which has a increasing trend with the increase of depth.The main controlling factors of shale gas accumulation of Lower Silurian Longmaxi Formation are the total organic carbon content,organic matter thermal mature degree,BET surface area,quartz content,mineral content in clay,pyrite content and preservation condition,of which organic carbon content has highest correlation with containing gas.On the whole,the gas content is high,which is decreased from the deep continental shelf to the shallow continental shelf environment.The shale gas mathematics model and geological model are established through multiple linear regression,favorable sections are mainly concentrated in the deep continental shelf,which have a higher organic carbon content and good preservation conditions,including high shale gas.Using multivariate progressive superposition method for optimization of favorable area optimization for Longmaxi Formation,including the favorable areas of southern Sichuan Zigong-Yibin-Luzhou,favorable areas of the favorable areas of Southeast Chongqing Fuling-Wulong-Qianjiang,West of Hubei Lichuan-Enshi-Wushan,Chongqing northeast Wuxi-Kaixian-Wanyuan.Based on the evaluation results of the favorable area,the 6 core favorable areas are selected,which has a certain reference value for the exploration of shale gas in the study area.