Impact of pressure solution creep on the performance of salt caverns for underground hydrogen storage

Underground hydrogen storage in salt caverns is a promising option for large-scale energy storage; however, its long-term integrity is governed by the time-dependent creep deformation of rock salt. While dislocation creep is commonly assumed to dominate cavern-scale behavior, increasing experimental evidence indicates that pressure solution creep can play a critical role under low-stress and low-temperature conditions. Nevertheless, its contribution at the field scale and under realistic operational scenarios remains insufficiently quantified. This study presents a three-dimensional numerical investigation of pressure solution creep and its impact on the mechanical behavior of salt caverns used for underground hydrogen storage. A three-dimensional modeling framework incorporating elastic deformation, dislocation creep, and pressure solution creep is implemented in the open-source finite-element simulator SafeInCave using Python. The constitutive model is calibrated against laboratory creep data from the literature over a wide range of stresses and temperatures, ensuring accurate reproduction of both linear (diffusion-controlled) and non-linear (dislocation-controlled) creep regimes. A comprehensive set of numerical experiments is conducted, covering caverns with regular and irregular geometries, varying depths, temperature conditions, and interlayer configurations, under both constant and cyclic gas pressure loading. The results reveal a clear spatial and temporal partitioning of deformation mechanisms. Dislocation creep dominates near cavern walls and in deeper, warmer formations, where deviatoric stresses and temperatures are high. In contrast, pressure solution creep becomes increasingly significant over time in shallow and colder formations, particularly in regions away from the cavern wall where von Mises stresses are low. Neglecting pressure solution creep leads to a systematic underestimation of long-term displacement and cavern convergence, especially under cyclic loading conditions relevant to hydrogen injection and withdrawal. Overall, the study demonstrates that pressure solution creep can govern long-term deformation in shallow or low-temperature salt formations and strongly influences stress redistribution and cavern convergence. Consequently, the explicit inclusion of pressure solution creep is essential for the reliable prediction of cavern performance, integrity assessment, and the safe design of underground hydrogen storage operations.