Comparative study on adsorption behaviors of CH4/CO2 and CH4/H2S in quartz nanopores from molecular perspectives: Implication for EGR in shale reservoirs

SY Zhan and SF Ning and JY Bao and J Wu and MS Zhang and JK Cui and XG Duan and XG Wang and YH Li, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 712, 136419 (2025).

DOI: 10.1016/j.colsurfa.2025.136419

Co-injection of H2S and CO2 offers a potential solution for the economical implementation of CO2 enhanced gas recovery (CO2-EGR) technique as it reduces the high cost of desulfurization. In this study, we employed Grand Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations to investigate the adsorption behavior of CO2/CH4 and H2S/CH4 mixtures within quartz nanopores. It is found that CO2 and H2S exhibit different adsorption structures when co-adsorbed on the quartz surface alongside CH4. Specifically, CO2 tends to adopt a parallel orientation, while H2S displays a perpendicular configuration due to hydrogen bonding interactions. The surface adsorption of CO2 is primarily governed by electrostatic interactions (approximately 62 %), while for H2S, the van der Waals and Coulomb interactions are comparable to each other. Additionally, the total interaction energy between H2S and the quartz surface is greater than that of CO2, attributed to the stronger van der Waals forces. Interestingly, although H2S demonstrates a stronger adsorption strength with the quartz surface, the displacement efficiency of CH4 in the adsorbed phase remains nearly the same. It should be attributed to the smaller molecular size of H2S compared to CO2, as it occupies less pore space with an equivalent number of molecules. This work provides valuable and novel insights into the competitive adsorption behaviors of CO2/CH4 and H2S/CH4, supplying the theoretic support for CO2/H2S co-injection projects in shale formations.

Return to Publications page