Hydro-mechanical continuum modelling of fluid percolation through rock salt

Salt caverns for storing renewably produced hydrogen underground pose a promising option to reduce CO2 emissions by improving the utilization of volatile renewable energy sources. Rock salt limits the infiltration of hydrogen into the storage cavern walls due to its favourable low permeability. However, pressure-driven percolation may create discrete pathways for the fluid and damage the cavern. Depicting this effect accurately in simulations may be crucial for assessing the long-term stability and integrity adequately. By introducing an extension to a deformation-dependent permeability model by Alonso, Olivella and Arnedo (2006) we can capture the non-linear feedback between salt deformation, permeability development and fluid migration using continuum models. Based on a quasi-isotropic arrangement of potential flow paths the model is able to reproduce pressure-driven percolation of hydrofrac experiments on rock salt specimens in terms of breakthrough pressure as well as preferential path orientation and locality. The model is implemented in the scientific open-source framework OpenGeoSys.