Influencing Factors of Gas Adsorption Capacity of Marine Organic Shale: A Case Study of Dingshan Area, Southeast Sichuan

The gas bearing property of marine shale is very important to the reserve calculation of shale gas field, which is directly related to the productivity and decline law of shale gas. The development of coastal shale gas is also the reserve field of shale gas exploration at present. Based on the conventional marine shale, this study adopts cylindrical shale core to measure the adsorption gas volume by testing the gas volume change in the process of pressure reduction and desorption of marine shale gas, simulates the conditions of different temperature, pressure, water cut, real pore structure and so on, and eliminates the negative adsorption anomaly of isotherm adsorption curve. The effects of organic matter content, pressure, temperature, water content and gas composition on the adsorption capacity of marine shale were analyzed. The experimental results show that the pressure condition controls the desorption process of shale gas, and the increase of pressure suppresses the desorption of shale gas. Within a certain range, with the increase of pressure, the adsorption gas volume of marine shale also increases. A large number of micropores of organic matter are developed, which greatly increases the specific surface area of organic matter. Under certain maturity conditions, with the increase of organic matter content, the adsorption volume of shale increases. The increase of temperature increases the activation energy of molecular surface and accelerates the desorption process of shale gas. When the shale is water-bearing, the water molecules occupy the active adsorption site on the shale mineral surface, which reduces the shale gas adsorption capacity. The research results have certain theoretical guidance for the exploration and development of coastal shale gas in the next stage.