Abstract: In order to work out the accurate amount of adsorbed gas in the highly evolved shale formation with rich organic matters, a new method was proposed to calculate the amount of adsorbed gas with different adsorption media considering formation water content after conducting isothermal methane adsorption and scanning electron microscopy experiments on highly evolved marine shale samples with rich organic matters from Longmaxi Formation, Southern Sichuan. Through the correction of organic matter adsorption fraction, the total amount of adsorbed gas on all pore surfaces of shale under stratigraphic conditions was converted into the amount of gas adsorbed by organic matters only on the organic matter pore surface. The results of the study show that the gas content calculated from the corrected amount of gas adsorbed by organic matters was basically consistent with the measured gas content on site. With the increase of organic matter content, the difference between the amount of gas adsorbed by organic matters and the total adsorbed gas amount of shale was decreased gradually, indicating that the corrected amount of gas absorbed by organic matters conforms to the actual methane adsorption model of the highly evolved shale formations with rich organic matters under stratigraphic conditions. This method can provide a basis for the calculation of adsorbed gas amount under the stratigraphic conditions of shale reservoirs.

Key words: shale gas, fluid distribution, amount of gas adsorbed, organic pore, gas content