The mechanisms of adsorption of methane (CH₄) and carbon dioxide (CO₂) are still a challenge in CO₂ sequestration with enhanced gas recovery (CS-EGR) in shale gas reservoirs. In this study, we focus on the adsorption behaviors of CO₂ and CH₄ on kerogen type IIIA using molecular dynamics (MD) and Grand Canonical Monte Carlo (GCMC) simulations. Simulation results indicated that the difference between the adsorption capacity of CO₂ and CH₄ increased with increase of mole fraction of CO₂. The adsorption capacity of CO₂/CH₄ decreased with increase of the water content. Water showed a greater effect on the adsorption of CO₂ than on that of CH₄. The isosteric heat and adsorption selectivity of CO₂/CH₄ decreased at low water content and increased with increasing water content. This study provides certain theoretical guiding significance for the application of CS-EGR projects from a microscopic perspective.

中文翻译：

---

对CO ₂，CH ₄及其混合物在IIIA型干酪根上的吸附机理的认识

页岩气储层中甲烷（CH ₄）和二氧化碳（CO ₂）的吸附机理仍然是挑战，因为CO _2的固存增加了天然气的采收率（CS-EGR）。在这项研究中，我们集中于分子动力学（MD）和大正则蒙特卡罗（GCMC）模拟中，CO ₂和CH ₄在IIIA型干酪根上的吸附行为。仿真结果表明，CO的吸附容量之间的差₂和CH ₄与CO的摩尔分数的增加而增加₂。CO ₂ / CH ₄的吸附量随着含水量的增加而减少。与CH ₄相比，水对CO ₂的吸附作用更大。在低水含量下，CO ₂ / CH ₄的等排热和吸附选择性随水含量的增加而降低。这项研究从微观角度为CS-EGR项目的应用提供了一定的理论指导意义。