(389k) Carbon & Hydrogen Geostorage: Nuclear Magnetic Relaxation and Diffusivity from Molecular Simulations

Geostorage of gases such as CO₂ and H₂ in shale formations is emerging as a promising pathway to support decarbonization, energy security, and long-term sustainability. While these formations have traditionally been exploited for methane production, their potential to serve as reservoirs for permanent CO₂ sequestration and reversible H₂ storage opens new technological frontiers.

This work investigates the rotational and translational dynamics of CO₂ and H₂ under a range of bulk pressures relevant to geostorage conditions. Differences in molecular properties—such as geometry, mass, and anisotropic intermolecular interactions—lead to distinct signatures in both nuclear magnetic relaxation and diffusivity. Simulations of bulk gases show good agreement with available experimental trends, capturing key aspects of fluid behavior relevant to geostorage scenarios.

While porous media have not yet been explicitly included in these simulations, the approach presented here has the potential to be extended to confined environments in future work. These findings have the potential to contribute to a deeper understanding of how gas molecules store, diffuse, and relax under subsurface conditions. By linking microscopic dynamics with macroscopic observables, this study has the potential to enhance our ability to evaluate and design geostorage strategies for both CO₂ and H₂ systems.