Cavern integrity under cyclic underground hydrogen storage in heterogeneous Brazilian pre-salt formations

Transitioning to cleaner energy sources is crucial for mitigating carbon dioxide emissions and addressing global energy challenges. Hydrogen has emerged as a solution, particularly due to its versatile applications in energy storage and generation. This research focuses on the hydrogen storage process in the Brazilian pre-salt caverns. It is motivated by its favorable characteristics, such as low permeability, creep behavior, self-healing, and competitive cost of salt caverns compared to other repositories. Hydrogen thermodynamics follows a diabatic solution that updates gas temperature and pressure in real time through a link between the CoolProp library and the in-house multiphysics and multiscale framework GeMA. Moreover, the research incorporates salt heterogeneities based on the well-log data from the Tupi field, providing a more accurate representation of Brazilian pre-salt field conditions and how different salt layers may affect the overall system. This approach allows for a comprehensive analysis of the cavern's response to hydrogen injection/discharge cycles, addressing both thermodynamic factors and geological variabilities often neglected by previous studies. The results demonstrated that salt rock heterogeneities may potentialize the extension of the zone with compromised integrity and induce significant permeability changes. It also offers valuable insights into the specific behavior of each type of salt rock during the hydrogen cyclic storage process.