Shale Gas Accumulation Conditions Analysis of Cambrian Xiaoyanxi Formation in Anhua Area of Hunan Province

In order to find out the shale gas exploration potential of Cambrian Xiaoyanxi Formation in the Anhua area, Hunan Province, based on the analysis of published shale gas drilling data, combined with field geological survey, magnetotelluric survey and analysis data, research on the shale development characteristics, organic geochemical index, rock and mineral composition, reservoir space, gas-bearing property and preservation conditions of Cambrian Xiaoyanxi Formation have been carried out in this study. The results show that the dark shale of Cambrian Xiaoyanxi Formation in the Anhua area is generally more than 100 m in thickness, developed with high organic carbon content, Type I organic matter and a high degree of thermal evolution; The content of brittle minerals in shale is high, and the lithofacies types are siliceous shale, including four micro pore types: dissolution pore, intergranular pore, mold pore and microfracture; The desorption gas content of drilling shale core was low, but the content of adsorbed gas was significantly higher under experimental conditions, indicating that the shale gas had escaped; The structures in the area are mainly open folds, and the faults are relatively undeveloped. The sealing ability of the shale roof is acceptable, but the siliceous rock in the floor develops high-angle fractures, which would easily become the escape channel for shale gas. The comprehensive analysis shows that the Cambrian Xiaoyanxi Formation in the Anhua area of Hunan Province has ideal material conditions for shale gas accumulation. However, the buried depth of the target layer at the drilling location is shallow and the floor sealing ability is inadequate, which is not preferable for the preservation of shale gas. The area close to the syncline core to the south provides better preservation conditions for shale gas and therefore should lead to certain exploration potential.