STUDY ON SHALE GAS ACCUMULATION MODEL IN YANGTZE REGION OF CHINA

Since Mesozoic, the Yangtze Platform in China has undergone strong uplift-fold movements, resulting in strong accumulation-loss adjustments of natural gas in marine shale during the late tectonic uplifts. The favorable areas for shale gas exploration are mainly located in the anticline and residual syncline of Longmaxi marine shale strata around Sichuan Basin. Therefore, this paper takes the marine shale gas around the Sichuan Basin and Xiuwu Basin as the research object to clarify the control effect of different structural styles on shale gas accumulation. The results show that: (1) The anticline structure around the Sichuan Basin is the favorable accumulation area of shale gas, which may be mainly related to the horizontal permeability of shale formation is far greater than the vertical permeability, and the shale gas gathers in the high part of the anticline; (2) The residual syncline also hosts a certain amount of shale gas, which is mainly related to the existence of shale gas adsorption zones under stratigraphic conditions. The existence of shale gas adsorption zones effectively reduced the shale gas permeability and slowed down the lateral loss of shale gas; (3) Shale gas accumulation may also occur in areas where reverse faults are developed, which shows that reverse faults can effectively block shale gas. In fact, the existence of shale gas adsorption zones can alleviate the dissipation of shale gas in various structural styles to a certain extent, which is conducive to shale gas accumulation. Nowadays, the marine shale strata in Yangtze area of China are characterized by the close overlap of anticlines, synclines and faults. Therefore, the accurate determination of favorable shale gas exploration areas requires comprehensive study of the control effect of various structural styles on shale gas accumulation.