A comparative study on transport and interfacial physics of H2/CO2/CH4 interacting with H2O and/or silica by molecular dynamics simulation

C Chen and J Xia, PHYSICS OF FLUIDS, 36, 016606 (2024).

DOI: 10.1063/5.0184754

Underground H-2 storage (UHS), i.e., injecting H-2 into subsurface geological formation and its withdrawal when needed, is identified as a promising solution for large-scale and long-term storage of H-2. In this study, molecular dynamics (MD) simulation was performed at a typical temperature 320 K with pressure up to 60 MPa to predict H-2 transport properties and H-2-H2O-rock interfacial properties, which are compared with those of CO2 and CH4. The MD results show that the CH4 profiles of property variations with pressure lie between those of H-2 and CO2 and more comparable to CO2. The interaction of H-2 with H2O/silica is much weaker than that of CH4 and CO2. It is found that the effect of H-2 pressure on altering the water contact angle and interfacial tension is negligible under all conditions. Unlike the multi-adsorption layers of the confined CO2 and CH4, there is only one adsorption layer of H-2 confined by silica nano-slit. The planar diffusion of H-2 in the confined system is slower than that in the bulk system at pressures lower than 20 MPa. The data and findings of this study will be useful for modeling the multiphase flow dynamics of UHS on reservoir scale, optimizing UHS operation, and assessing the performance of a cushion gas, e.g., CO2 or CH4. (C) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)

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