Reservoir-forming conditions and favorable exploration zones of shale gas in Lower Silurian Longmaxi Formation of Sichuan Basin

There develops shale with rich organic matters in Longmaxi Formation of the Lower Silurian in Sichuan Basin.This shale with a great thickness is the source of shale gas and widely distributed in the basin.As the source,the shale is characterized as high organic content,good organic type and high organic thermal evolution degree.As the reservoir,there exits great quantity of cracks,porous and wrinkles,which offers sufficient accumulated space for shale gas.The isothermal adsorption test shows that the shale has strong ability of gas adsorption.The structural condition in this basin is available for forming shale gas reservoir.The gas shows of many wells drilled in the shale strata of the Lower Silurian in this area indicated the great potential of shale gas.The shale indexes of thickness distribution,organic carbon content,thermal evolution degree and gas generation level in Sichuan Basin show that Yibin-Zigong-Luzhou and Dazhou-Wanxian areas are the favorable zones for shale gas exploration.