Adsorption and Diffusion Behaviors of CO2 and CH4 Mixtures in Different Types of Kerogens and Their Roles in Enhanced Energy Recovery

Abstract

CO2 geological sequestration in subsurface shale formations is a promising strategy to store CO2 and to increase shale gas production. The understanding of gas adsorption and diffusion mechanisms in microporous media is critical for CO2 storage-enhanced gas recovery (CS-EGR). The type of kerogens is one of the important factors that influence the adsorption and diffusion behaviors of gases. In this work, the Grand Canonical Monte Carlo and Molecular Dynamics simulations were utilized to develop kerogen models and further investigate gas and water adsorption and diffusion behavior on the type IA, IIA, and IIIA kerogen models. The results indicated that the adsorption and diffusion capacities of CO2 are larger than those of CH4. The adsorption and diffusion capacity decreased with increasing water content. However, the CO2/CH4 adsorption selectivity increased with the increase in water content. Type IIIA demonstrated the best potential for adsorption and diffusion. This study provides insights into the role of the adsorption and diffusion behavior of CO2 and CH4 mixtures on kerogens of different types under different water contents at a microscopic scale, and can facilitate further understanding of the processes involved in CO2 storage coupled with enhanced energy recovery.