Fully coupled hydro-mechanical–chemical continuum modeling of fluid percolation through rock salt

Abstract

In domal and bedded rock salt geothermal reservoirs, geochemical dissolution of the in-situ rock salt formation can alter fluid transport properties, thus impacting fluid flow. Coupled Hydro-mechanical–chemical (HMC) modeling is a useful tool to evaluate fluid transport through rock salt geothermal systems and to assess their economic potential. Existing continuum-based numerical simulation of fluid transport through rock salt relies on the polyhedral orientation of rock salt crystal boundaries as potential fluid pathways, employing a deformation-dependent permeability model to depict pressure-driven fluid flow through rock salt. However, this numerical approach is exclusively HM-coupled and overlooks the influence of halite dissolution/precipitation on the permeability model. This study extends the deformation-dependent permeability model to account for halite dissolution by adopting a reverse mineral growth approach. Using this extended (HMC-coupled) model, we capture the relevance of geochemical reactions on the response of rock salt formations undergoing pressure-driven fluid percolation. The resulting simulations predict a lower fluid pressure than the HM-coupled scenario, highlighting the impact of halite dissolution on fluid flow through rock salt.