Occurrence characteristics and enrichment regularities of CH4 and CO2 in clay reservoirs: Implication for in-situ CO2 sequestration with shale gas recovery

作者：Peng Xu, Yu Qian, Xiaoqiang Liu, C.C. Liu, Ye Ni, Jia Jia, Meijun Li, Zeqin Chen · 发表于：Journal of Molecular Liquids · 年份：2025 · DOI：10.1016/j.molliq.2025.127710 · 被引用次数：4 · 研究领域：Hydrocarbon exploration and reservoir analysis、Atmospheric and Environmental Gas Dynamics、Hydraulic Fracturing and Reservoir Analysis

Understanding the in-situ occurrence states and enrichment characteristics of CH 4 and CO 2 in shale reservoirs is a prerequisite for optimizing the approach of CO 2 sequestration with enhanced gas recovery (CS-EGR) technology. The divergent structural characteristics of montmorillonite (high surface area/swelling capacity) and illite (stable framework) critically govern gas adsorption and transport dynamics in shale formations. In this work, composite clay reservoirs comprised of montmorillonite and illite were modeled to investigate the adsorption behaviors of CH 4 and CO 2 at actual geological depth by molecular simulations. Density functional theory calculations demonstrate the physisorption manners of CH 4 and CO 2 on heterogeneous clay surfaces. Al- and Mg-doped sites show preferential adsorption to gas molecules, particularly to CO 2 . Based on grand canonical Monte Carlo and molecular dynamics simulations, the density distributions, adsorption capacities and absorption heats of CH 4 and CO 2 were analyzed to characterize their in-situ occurrence states and enrichment regularities as well as the efficiency of CO 2 displacing CH 4 . The enrichment region of adsorbed CH 4 is predicted to be beyond 3200 m, while the optimal depth for CO 2 storage is around 800 m, accounting for the high CH 4 displacement efficiency. A CO 2 /CH 4 pressure ratio of 1/4 was found to be economically favorable for efficient displacement of adsorbed CH 4 . These findings have clarified the adso...