Preliminary Laboratory Studies on Hydrogen Storage in a Salt Cavern of the Eocene Barbastro Formation, Southern Pyrenees, Spain

The transition to a greener economy requires scalable, reliable, and efficient energy storage solutions. Hydrogen (H₂), a key component of future renewable energy systems, must be stored in gigaton-scale quantities to balance supply and demand globally. Underground hydrogen storage (UHS) in salt rock caverns is emerging as the most promising solution due to the exceptional properties of rock salt (halite), such as low permeability, self-healing capacity, and geochemical stability. However, significant scientific and technological challenges remain, requiring further study to ensure the safe and efficient deployment of this technology (Berrezueta et al., 2024).

Among these challenges, the geomechanical and geochemical evolution of rock salt during cyclic H₂ injection and extraction requires further knowledge to address potential integrity problems of the reservoir. Key uncertainties arise from the complex interplay of heterogeneous mineralogy, variable brine compositions, and the dynamic temperature and pressure conditions within the reservoir. Addressing these uncertainties begins with the development of a robust laboratory testing protocol to simulate and analyze the interaction of hydrogen within rock salt under reservoir-like conditions.

This study presents experimental data from an autoclave setup designed to replicate reservoir conditions of pressure and temperature. Samples of the Eocene Barbastro Fm. (Southern Pyrenees) were obtained from a deep borehole drilled in a salt structure considered for hydrogen storage. The experiments using pure halite samples and halite with various impurities provide insights into the reactivity of non-halite phases and their impact on the properties of the rock salt. The findings contribute to addressing critical knowledge gaps and improving the safety and reliability of underground hydrogen storage in salt caverns. By advancing our understanding of the processes governing UHS in salt formations, this research supports the development of robust, science-based solutions for the global energy transition.

This work is funded by the Project UES365 of the Convocatoria Misiones-CDTI (Spain).

References:

Berrezueta, E.; Kovács, T.; Herrera-Franco, G.; Caicedo-Potosí, J.; Jaya-Montalvo, M.; Ordóñez-Casado, B.; Carrión-Mero, P.; Carneiro, J. Laboratory Studies on Underground H₂ Storage: Bibliometric Analysis and Review of Current Knowledge. Appl. Sci. 2024, 14, 11286. https://doi.org/10.3390/app142311286