Shale rocks comprise of a lager proportion of clay minerals; shale gas potentially adsorbs on the clay minerals due to its large specific surface area. In this work, selective adsorption behaviors of CO₂/CH₄ are investigated in clay-mineral nanopores using the grand canonical Monte Carlo (GCMC) simulation method. In addition, the subsequent implications for CH₄ recovery and CO₂ sequestration are summarized. Results show that CH₄ exhibits the strongest adsorption on kaolinite, followed by that on illite and montmorillonite, while adsorption capacity of CO₂ is calculated in the order of montmorillonite > illite ≈ kaolinite, suggesting that CO₂ injection has the best performance for CH₄ recovery when implemented in montmorillonite-rich shale reservoirs. Comparatively, smaller pores are dominated by the adsorbed gas and are also favorable for CO₂ sequestration. The adsorption selectivity of CO₂ over CH₄ on clay minerals is predicted in the order of kaolinite < illite < montmorillonite; moreover, the adsorption selectivity is reduced as pressure decreases for illite and montmorillonite, implying that the injection pressure of CO₂ should be low enough to achieve an efficient CH₄ recovery and CO₂ sequestration. However, the ideal injection pressure of CO₂ should be around the pressure where it has the maximum adsorption selectivity for kaolinite-rich shale. This study may achieve a deeper understanding of the adsorption behavior of CO₂/CH₄ in clay-rich gas-bearing reservoirs; furthermore, it may provide the guidelines for future optimization design of CO₂ injection for CH₄ recovery and CO₂ sequestration in the field applications.

页岩包括大量的粘土矿物。页岩气由于其较大的比表面积而可能吸附在粘土矿物上。在这项工作中，使用大正则蒙特卡罗（GCMC）模拟方法研究了在矿物矿物纳米孔中CO ₂ / CH _4的选择性吸附行为。另外，总结了对CH ₄回收和CO ₂隔离的后续含义。结果表明，CH ₄在高岭石上表现出最强的吸附，其次在伊利石和蒙脱石上，而对CO _2的吸附能力按蒙脱石>伊利石≈高岭石的顺序计算，表明CO ₂当在富含蒙脱石的页岩储层中实施时，注水具有CH ₄回收的最佳性能。相比之下，较小的孔被吸附的气体所主导，并且也有利于CO ₂隔离。根据高岭石<伊利石<蒙脱石的顺序，预测了CO ₂对CH ₄的吸附对粘土矿物的选择性。此外，随着对伊利石和蒙脱石的压力降低，吸附选择性降低，这意味着CO ₂的注入压力应足够低以实现有效的CH ₄回收和CO ₂隔离。但是，理想的CO ₂注入压力对于富含高岭石的页岩，其最大吸附选择性应在压力附近。这项研究可以更深入地了解富含粘土的含气储层中CO ₂ / CH ₄的吸附行为。此外，它可以为将来在现场应用中用于CH ₄回收和CO ₂隔离的CO ₂注入优化设计提供指导。