Molecular Insights into Competitive Adsorption of CO2/CH4 Mixture in Shale Nanopores

The rapidly expanding realm of shale gas recovery has prompted the scientific community to evaluate alternative methods for enhanced extraction. One such avenue of exploration, as documented in this study, is the competitive adsorption behavior of a supercritical carbon dioxide (CO2) and methane (CH4) binary mixture in shale organic nanopores. Utilizing grand canonical Monte Carlo (GCMC) simulations, this behavior was modeled and subsequently validated against empirical data, revealing a good alignment between the two.

The study's key findings are insightful: CO2 exhibits a markedly higher adsorption capacity in shale organic nanopores than CH4 under a multitude of conditions. In-depth examination reveals that temperature plays a pivotal role in the adsorption dynamics. Specifically, lower temperatures amplify both the quantity of adsorption and the selectivity for the CO2/CH4 binary mixture. However, the ideal CO2 injection pressure should strike a balance between maximizing CO2 sequestration and optimizing shale gas extraction. Intriguingly, the presence of moisture in the shale introduces a variable effect on the adsorption selectivity for CO2/CH4. At low moisture levels, its influence is markedly different than at higher levels, necessitating adaptive simulation strategies based on the moisture context of individual shale reservoirs.

This work is poised to offer invaluable insights into the intricacies of shale gas recovery. By underscoring the pivotal role of factors such as temperature, pressure, pore size, and moisture content in the competitive adsorption process, it emphasizes the need for targeted strategies. Ultimately, the findings can guide the development of more efficient practices for shale gas extraction and CO2 sequestration in shale formations, addressing both energy and environmental concerns.