Exploration potential for shale gas in the Upper Permian Longtan Formation in eastern Sichuan Basin

Based on the previous studies and in combination with field geological investigation and drilling data analysis, the research indicates that the thickness of the organic rich shale in the Upper Permian Longtan Formation in the eastern Sichuan Basin is generally over 50 m with the maximum thickness of 140 m. Lithological association varies significantly in both vertical and horizontal direction: there mainly developed shale with limestone interbed in the Yunyang-Tongjiang area in the north, shale with coal seam and limestone interbeds in the Guang'an area in the central, as well as shale with sandstone and coal seam interbeds in the south. The total organic carbon contents (TOC) are generally higher than 2%; Research on carbon isotopic composition of the shale kerogen and the organic petrology indicates that the organic matters are mainly of type II with excellent hydrocarbon generation potential. Analysis of X-ray diffraction and vitrinite reflectance indicates that the shale has a high content of brittle minerals such as quartz and displays a high evolution degree with favorable fracturability. The gas logging during drilling inthe Longtan Formation shale displays significant abnormity, reflecting the favorable gas potential. The prediction of shale gas resource suggests largeresource potential and exploration prospect for shale gas. A comprehensive analysis indicates that there have favorable exploration prospect for shale gas in Wanxian-Yilong-Tongjiang-Fengjie area in the north and the Yibin and Yongchuan-Xijiang-Chishui area in the south. ©, 2015, Oil and Gas Geology Editorial Board. All right reserved.