Underground gas storage

Storing hydrogen underground introduces additional challenges compared to conventional gas storage. Hydrogen interacts differently with subsurface materials and exhibits complex phase behavior, requiring advanced simulation tools to accurately model thermodynamic, multiphase, and geomechanical processes.

Our research addresses these challenges by developing and applying advanced thermodynamic models for hydrogen–brine systems. These models are used to compile accurate phase-equilibria (PVT) data and integrate them into standard black-oil simulators. A key component of our work is the open-source MATLAB Reservoir Simulation Toolbox (MRST), which includes a specialized module—h2store—for simulating underground hydrogen storage.

The h2store module offers simulation capabilities for hydrogen–brine mixtures based on robust physical models. Key features include:

• Implementation of the Redlich-Kwong (RK) equation of state for H₂–brine systems.
• Tools for precomputing and tabulating PVT data to support black-oil simulations.
• Access to solubility tables derived from electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) data and Henry’s law correlations for accurate gas–liquid equilibria.
• Correlations for computing hydrogen and water density under reservoir conditions.

These capabilities allow us to explore essential aspects of underground hydrogen storage, such as the effect of salt concentration, solubility dynamics, and operational factors like injection/withdrawal rates and cycling frequency. Our goal is to enable accurate and efficient modeling of hydrogen storage in geological formations, particularly saline aquifers, to support the deployment of hydrogen as a large-scale energy carrier.

References

• E. Ahmed, O. Møyner, X. Raynaud, and H. M. Nilsen. Phase behavior and black-oil simulations of Hydrogen storage in saline aquifers. Advances in Water Resources, Volume 191, September 2024, 104772. DOI: 10.1016/j.advwatres.2024.104772