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Cyclic Energy Storage in Salt Caverns: nonlinear finite-element modelling of rock salt creep at reservoir scale

Subsurface formations provide giant capacities for renewable energy storage, when this energy is converted to green fuels such as hydrogen. A promising option for storing large-scale quantities of hydrogen is in subsurface rock salt caverns. Rock salts, however, are known to exhibit nonlinear time-dependent creep deformation. In this work, the complex creep behaviour of rock salt caverns is modelled and simulated through a 2D finite element model using unstructured grids. The developments presented allow for quantification of the state of the stress around the cavern with the aim of aiding assessments of the safety and reliability of the structure in the longer term. The study builds on the principle of minimum potential energy to consistently account for the nonlinear creep deformation using finite elements. Cyclic loading and evolution of damage within the material are incorporated to predict the failure of the material over time. Sensitivity analysis of key parameters is performed to understand the influence of creep on deformation and stress evolution around the salt cavern configurations. The simulator developed in this work is publicly available at this https URL.