Impact of geothermal gradients on diffusive transport in subsurface gas storage

Determine the effect of geothermal temperature gradients on the diffusive transport of dissolved carbon dioxide (CO2) and hydrogen (H2) in saline reservoir porous media containing capillary-trapped gas ganglia, including whether and how geothermal gradients alter the directionality and magnitude of Ostwald ripening-driven mass flux between the aqueous phase and trapped ganglia at storage-relevant depths.

Background

The paper examines diffusive transport processes in subsurface storage of CO2 and H2, emphasizing the role of capillary-trapped ganglia and the partitioning of gases between bulk and dissolved phases. Previous analyses have primarily considered isothermal conditions and often assumed ideal gas behavior, which the authors argue is inadequate for geologic storage environments.

The authors note that, prior to this work, the influence of geothermal gradients on diffusive transport and Ostwald ripening in subsurface reservoirs had been sparsely treated in the literature and explicitly identified as unresolved. They position their thermodynamics-based analysis to address this gap, highlighting non-ideality, entropic contributions, and thermodiffusion as critical factors.