Optimizing CO₂ storage and CH₄ recovery: An integrated model of geophysical trapping dynamics in shale nanopores

Carbon geological storage (CGS) plays a pivotal role in curbing Carbon Dioxide (CO₂) emissions and achieving the global 2050 Net-Zero targets. This study presents an innovative approach by integrating CGS with Methane (CH₄) production in shale gas formations, offering a dual benefit of efficient CO₂ storage while enhancing CH₄ recovery from previously trapped reserves. An in-house sophisticated MATLAB code has been utilized in this research to further delve and unlock the geophysical trapping dynamics within both organic and inorganic shale nanoporous systems. Key mechanisms, such Knudsen diffusion, molecular and surface diffusion, as well as viscous and slip flow, are rigorously analyzed and coupled with adsorption–desorption dynamics using the BET isotherm equation. The findings reveal that enhanced CO₂ adsorption in high organic content shales is most favorable under high-pressure and low-temperature conditions, where CO₂ outcompetes CH₄ for adsorption sites, revealing a pronounced adsorption selectivity in favor of CO₂. This study further identifies optimal conditions for maximizing CO₂ sequestration while ensuring significant CH₄ recovery. The strategic utilization of post-stimulated shale reservoirs for CO₂ storage presents a powerful opportunity: not only does it contribute to climate change mitigation, but it also promotes CH₄ recovery via desorption by optimizing CO₂ injection strategies. Understanding the geophysical dynamic mechanisms highlighted in this research during CO₂ injection is critical for unlocking the full potential of this approach, making it a promising solution for both carbon management and energy production.