Gas bearing potential and exploration strategy of organic shale in Guangxi

In order to deepen the understanding of shale gas-bearing potential in Guangxi, the authors in this research analyzed the gas-bearing potential of key organic-rich shale layers in Guangxi and the controlling factors of shale adsorbed methane gas volume, and discussed the favorable distribution area and exploration countermeasures of gas-bearing potential layers, through shale isothermal adsorption experiment method combined with TOC content, organic matter type, vitrinite reflectance (R_O), whole rock and clay X-ray diffraction analysis and testing. The study shows that the shale of Luzhai Formation has the best gas potential, and the average saturated adsorption capacity is 2.87 m³/t, followed by Luofu Formation, Qingxi Formation, Shengping Formation, and Shipao Formation. The areas with the best shale adsorption performance are Shanglin and Nandan in Luofu Formation, Nandan-Liuzhou and Mashan Zhoulu in Luzhai Formation, and Shangsi in Shipao Formation. The main factors controlling the methane gas adsorbed by shale in Guangxi include TOC content, organic matter type, R_O, pore volume of mesopore and micropore, content of illite /smectite mixed layers, and caprock conditions, but the main controlling factors of different shale layers are slightly different. In general, the exploration evaluation should focus on finding out the sedimentary microfacies, TOC content of shale, clay mineral types and relative content, structure and caprock preservation conditions. For areas with strong structural activity and high R_O, the exploration principle of “looking for static in motion and selecting low from high” should be followed. The study aims to guide the exploration and development of shale gas in Guangxi for a new breakthrough.