Hydrogen storage in saline aquifers: Opportunities and challenges

Hydrogen (H2) is a vital component of future decarbonized and sustainable energy systems. As an energy carrier, hydrogen can play a significant role in the security, affordability, and decarbonization of energy systems. Aquifers are the second-most economically-attractive option for geological hydrogen storage after depleted oil and gas reservoirs. For a successful storage project, a reasonably-high recovery of stored hydrogen is projected. Aquifers represent the most environmentally-friendly type of underground storage and are sometimes the only accessible geological formations for hydrogen storage. The selection of suitable storage sites is an inevitable step in the development of large-scale hydrogen storage operations. Storage sites should be selected based on sustainability, considering accessibility to the distribution system, the construction cost, environmental limitations, and legal and social requirements. Characterizing the mechanisms and parameters controlling the subsurface hydrogen transport properties is critically important for accurately assessing storage features and resolving hindrances toward the implementation of large-scale hydrogen storage. Research and demonstration programs are required to fully understand involved processes and their role in storage operations, design efficient injection and production strategies, and evaluate the po-tential hazards and the opportunities for their reduction. There is a crucial need for a dynamic regulatory framework and participation strategy facilitating large-scale aquifer storage. Hydrogen storage projects require a high level of safety regulations, especially for the leakage detection and monitoring, surface facilities, and op-erations - these are essential for designing a safe and efficient aquifer storage operation.