|Abstract:The Permian Longtan Formation is one of the most important shale gas exploration strata of marine-continental transitional facies in Sichuan Basin. Based on drilling core and thin section observation, X-ray diffraction analysis, scanning electron microscopy, organic geochemical analysis, porosity and permeability testing, in-situ gas content analysis and Langmuir adsorption isotherm, taking Well SD1 as an example, the characteristics of source rock and shale gas potential of Longtan Formation in Shibao mining area, southeast Sichuan were studied. The results show that: 1) The cumulative thickness of shale in Longtan Formation is about 47.74 m, which interinteracts with coal seam and fine sandstone, and is mainly deposited in microfacies of interdistributary bay and marsh. 2) The shale is characterized by high clay mineral content (49.7% on average), rich in siderite, pyrite and anatase, and lack of feldspar and carbonate minerals. 3) The organic matter is mainly composed of vitrinite. The δ13C of kerogen is concentrated in the range of -22.8 ‰ to -24.2 ‰. The Longtan shale has high total organic carbon (TOC) of 7.37% and contains type III gas-prone organic matter. The thermal evolution of organic matter is in the over-mature stage, showing good hydrocarbon potential. 4) The pore types mainly include microfractures, organic matter pores, dissolution pores and intercrystalline pores. The porosity varies from 3.05% to 4.35% with an average of 3.79%. The permeability is about 0.486μD, far below 1mD. Therefore, Longtan Formation is an obvious ultra-low porosity and ultra-low permeability reservoir. 5) The in-situ gas content of shale varies from 0.61m3/t to 4.70 m3/t, with an average of 2.16 m3/t, indicating relatively high gas content. Saturated adsorption gas content is greater than 2.00 m3/t, showing good adsorption performance. Generally, the comprehensive study shows that the shale gas development potential of Longtan Formation is great in Shibao mining area, and the C13-C15 carbonaceous mudstone/shale with coal seam assemblage in the middle part of upper Longtan Formation and the C17-C24 carbonaceous mudstone/shale with coal seam assemblage in the upper part are the main exploration sections.