Abstract: Objective Under the global carbon peaking and carbon neutrality targets, hydrogen has emerged as a critical carrier linking renewable energy sources with end-use sectors, playing a strategically significant role in the transformation of energy structures. Underground hydrogen storage (UHS) represents a promising technology for large-scale hydrogen storage, effectively addressing the intermittency and volatility of wind and solar power while enabling large-scale, long-duration energy storage. Among various UHS options, depleted gas reservoirs offer exceptional advantages, including large storage capacity, proven caprock sealing integrity, reuse of existing facilities, and the availability of residual natural gas as cushion gas, positioning them as the most promising candidate for future large-scale hydrogen storage applications.
Methods This study employs a literature review combined with inductive-deductive reasoning to systematically integrate domestic and international research outcomes in the field of UHS. The analysis focuses on four core challenges in depleted gas reservoir storage: multiphase flow instability, multi-field coupling-induced hydrogen loss, wellbore hydrogen embrittlement and integrity deterioration, and multi-energy flow integration. On this basis, targeted technology development pathways and future research directions are proposed.
Results The results indicate that internationally, UHS has progressed to the demonstration stage, with Europe and the United States taking the lead. Although China possesses substantial geological resource potential, it lags notably behind in engineering experience, fundamental research, and standardization systems, facing challenges such as complex multiphase flow behavior, significant hydrogen loss, high risks of wellbore hydrogen embrittlement, and inadequate multi-energy integration capabilities. Through comprehensive analysis, this study develops a field-scale numerical modeling framework integrating equations of state for hydrogen, multiphase flow equations, chemical reaction kinetics, and microbial growth models. It reveals the general rule that cushion gas molecular weight affects hydrogen recovery efficiency, with methane yielding the best performance (89.7%) and carbon dioxide the lowest, and elucidates the differentiated regulation pathways of methanogens and sulfate-reducing bacteria on hydrogen loss and reservoir petrophysical properties. Furthermore, the paper proposes a full-cycle “three-in-one” integrity management technical specification covering caprock sealing, wellbore integrity, and cyclic loading response, alongside a flexible collaborative regulation model for the entire chain of “green hydrogen production – underground storage – pipeline transmission – terminal utilization.”
Conclusions Future efforts should focus on accelerating demonstration projects within the framework of integrated energy-matter network planning, making breakthroughs in multi-field coupled simulation, microbe-mineral-fluid interactions, and hydrogen-electricity-gas synergy regulation, while refining standardization and safety systems. These efforts will drive depleted-gas-reservoir hydrogen storage to become a core pillar supporting large-scale energy storage and seasonal peak-shaving.