Hydrogen is increasingly viewed as a critical energy carrier capable of supporting decarbonization across sectors such as industry, transportation, and power generation. Unlike fossil fuels, hydrogen combustion produces no direct carbon dioxide emissions.

However, large-scale deployment of hydrogen technologies requires reliable methods for storing vast amounts of hydrogen to balance supply and demand, particularly for seasonal energy storage. Surface storage solutions, such as pressurized tanks, are costly and limited in capacity. For this reason, scientists are exploring underground hydrogen storage (UHS) in geological formations.

Among the potential underground storage options - such as saline aquifers, salt caverns, and coal seams. Depleted oil and gas reservoirs stand out as particularly attractive candidates. These reservoirs have already stored hydrocarbons for millions of years and possess well-characterized geological properties, including high storage capacity, established infrastructure, and reliable caprock integrity.

The review highlights several advantages of using depleted reservoirs for hydrogen storage, including reduced development costs due to existing wells and infrastructure, as well as detailed geological data collected during previous hydrocarbon production.

At the same time, the authors note that hydrogen storage in such formations presents unique challenges. Hydrogen’s low density and high diffusivity can lead to rapid migration within the reservoir. Chemical and microbial reactions may also convert hydrogen into other gases such as methane or hydrogen sulfide, potentially reducing storage efficiency.

The study examines the complex physical and chemical mechanisms that influence hydrogen storage underground. These include structural and capillary trapping processes, geochemical reactions between hydrogen and reservoir minerals, and interactions between hydrogen, brine, and residual hydrocarbons.

The authors also review key reservoir parameters that affect hydrogen storage performance, including permeability, porosity, wettability, fluid density and viscosity, and interfacial tension between hydrogen and reservoir fluids. By compiling data from recent laboratory experiments and numerical simulations, the study provides a detailed overview of how these factors interact during injection and withdrawal cycles.

Hydrogen’s high flammability and unique physical properties also raise safety concerns in laboratory and industrial environments. The review summarizes known hydrogen incidents and proposes safety guidelines for laboratory experiments and hydrogen handling, highlighting the importance of appropriate monitoring systems, ventilation, and operational procedures.

According to the authors, depleted hydrocarbon reservoirs could play a crucial role in enabling large-scale hydrogen deployment. Compared with other underground storage options, these reservoirs offer lower capital costs and potentially greater storage capacity.

However, the study emphasizes that further experimental and field-scale research is required to better understand hydrogen behavior in complex subsurface environments.

By consolidating current knowledge and identifying key research gaps, the review provides a valuable roadmap for scientists, engineers, and policymakers working on hydrogen storage technologies.