Molecular Simulation and Experimental Study on Adsorption Effect of CH₄/CO₂ in Shale Minerals

Abstract

This study adopted volumetric method experiments to explore the single-component methane and carbon dioxide adsorption characteristics of typical minerals under complicated conditions. Moreover, the fitted models such as Henry, Langmuir, and Freundlich models were employed to optimally characterize the adsorption process. On this basis, the grand canonical Monte Carlo (GCMC) method was carried out to investigate and verify the CH 4 /CO 2 adsorption rules of typical minerals under the same conditions microscopically. The results suggested that the adsorption amount increased at relatively higher temperatures (70−130 °C) and lower pressures (0−6 MPa); besides, carbon dioxide was more likely to be adsorbed. Under the same conditions, the CH 4 /CO 2 adsorption amounts followed the order of montmorillonite > calcite > illite. In addition, minerals with greater specific surface area, greater pore volume, and smaller average pore size had greater adsorption capacities for gases. The Freundlich model achieved the optimum degree of fitting for the adsorption rules of methane and carbon dioxide among the three minerals. With regard to mineral adsorption capacities and gas competitive adsorption relations, the GCMC method-based molecular simulation attained relatively higher goodness of fit with experimental results. This study provides basic data and theoretical foundation for carbon dioxide displacement of shale gas technology under specific environment.