Molecular simulation on competitive adsorption mechanism of CH4/CO2 on shale kerogen

Due to the fact that most shale gas is stored in the adsorption state on organic compounds of the formation, better understanding of adsorption mechanism of CH4/CO2 in shale kerogen not only contributes to figure out the reserves of shale gas but also is beneficial to shale gas exploitation and carbon sequestration. Using the basic experimental data of shale core from Yanchang Formation, Ordos Basin, China, four types of kerogen structure are constructed and used as inputs to molecular simulation. The isothermal adsorption capacity of single-component and bi-component of CH4 and CO2 on kerogen is simulated and analyzed. The results indicate that the isothermal adsorption capacity of CH4/CO2 increases with the rising of maturity but decreases with temperature. The effect of kerogen type on adsorption capacity is as follows: type III > type II > type I. And the adsorption capacity of CO2 is larger than that of CH4, indicating the good potential of enhancing shale gas production and carbon sequestration.