Preservation mechanism of Fuling shale gas

The essential difference between conventional gas and shale gas in reservoir space is the difference in pore size or pore structure. The shale burial history, gas content, production data and isotope fractionation of desorbed gas in the Jiaoshiba area of Fuling, Sichuan Province indicate that shale gas was stored in the inter-connected pore units formed by single or multiple organic matter types, and its preservation mechanism was attributed to capillary pressure and static water pressure. Therefore, tectonic structure or trap shape has little impact on shale gas enrichment. The destruction of shale gas preservation conditions by tectonic activity was mainly determined by the decrease of static water pressure caused by tectonic movements, the destruction of lamination caused by geologic stress, and the decrease of capillary sealing ability caused by the opening of lamellae under horizontal compression conditions. Faults releasing tectonic force would not cause further destruction of lamination. On the contrary, they might be helpful for the preservation of a footwall which could be the optimum shale gas target. The recovery ratio of shale gas could be derived from the theory of capillary pressure, which would supply guidance for production.