A Review of Underground Hydrogen Storage in Depleted Oil and Gas Reservoirs

As hydrogen assumes an increasingly strategic role in the global energy transition, the development of efficient, safe, and cost‐effective large‐scale hydrogen storage systems has become a critical enabler for the hydrogen economy. Underground hydrogen storage (UHS), particularly in depleted oil and gas reservoirs, is gaining traction as a promising solution for seasonal energy balancing and the integration of intermittent renewable energy sources. This review provides a comprehensive synthesis of current international progress in pilot projects, experimental investigations, and numerical simulations related to UHS in depleted reservoirs. Key scientific challenges are examined, including reservoir suitability, caprock integrity, wellbore sealing performance, material durability, and coupled geochemical–microbial processes. Hydrogen’s high diffusivity, mobility, and chemical reactivity present unique risks in the subsurface, thereby increasing the likelihood of leakage and reservoir destabilization. To date, no commercial‐scale project has successfully demonstrated pure hydrogen storage in depleted reservoirs, and most current studies remain at the modeling or laboratory scales, lacking standardized risk assessment protocols and monitoring frameworks. This review provides critical insights for assessing the feasibility of UHS in depleted reservoirs and underscores the urgent need for integrated research on coupled hydro‐biogeochemical‐mechanical processes, hydrogen‐compatible materials, site selection criteria, and long‐term monitoring technologies.