关键词: 页岩气, 龙马溪组, 牛蹄塘组, 有机质孔隙, 热演化, 重庆周缘

Abstract: In the exploration and development process of shale gas in Niutitang Formation, there are problems such as low gas production and short duration. By comparing the Lower Silurian Longmaxi shale in southeastern Chongqing with the Lower Cambrian Niutitang shale in northeastern Chongqing, the pore reservoir capacity and evolution characteristics of the two sets of shale were analyzed. The results show that there are significant differences in organic pore development characteristics of the Longmaxi shale and the Niutitang shale. The organic pores inside solid kerogen in the Longmaxi shale have a small number, small pore size and poor connectivity, but the amount and size of organic pores in pyrobitumen are large, and the connectivity is good. The solid kerogen and pyrobitumen in the Niutitang shale do not develop organic pores. The degree of reservoir thermal evolution has a direct control effect on the development of organic pores in shale. The Longmaxi shale is relatively weak in thermal evolution as palaeo-buried depth is shallower than the Niutitang shale. The appropriate degree of thermal evolution preserves a large amount of organic pores in the pyrobitumen of the Longmaxi shale, but the solid kerogen has a relatively long evolution time and the number of organic pores decreased. The palaeo-buried depth of the Niuzhitang shale in northeastern Chongqing is too large, and reservoir reached the metamorphic period due to excessive evolution, resulting in the absence of organic pores in the solid kerogen and pyrobitumen. For the efficient exploration and development of shale gas in the Niutitang Formation, a shale distribution area with moderate thermal evolution should be sought.

Key words: shale gas, Longmaxi Formation, Niutitang Formation, organic pores, thermal evolution, periphery of Chongqing