Insights and Strategies for Underground Hydrogen Storage Optimization

Abstract Underground Hydrogen Storage (UHS) is a promising solution for facilitating the transition to a net-zero energy landscape. Hydrogen is an excellent energy carrier that can be utilized to store surplus energy from renewable sources and later release it in periods of high-power demand. The objective of this paper is to investigate the optimal operating conditions for underground hydrogen storage and present guidelines that can enhance the utilization of the selected storage site. The methodology of this study involves conducting numerical simulations on a synthetic model that replicates the characteristics of a heterogeneous field with two anticlines. The analysis is conducted on two cases representing a depleted gas reservoir and a saline aquifer. Key operational control parameters such as well count, bottom-hole pressure (BHP) limits, injection/production cycle duration, perforation interval, and cushion gas injection play pivotal roles. These operational parameters will be systematically varied to assess their impacts on hydrogen storage capacity, deliverability, and purity. The results are analyzed by implementing advanced reservoir engineering practices that delineate significant differences between depleted gas reservoirs and saline aquifers in terms of storage parameters and hydrogen recovery. The proposed operational guidelines are based on water production, pressure maintenance, and hydrogen purity. Bottom-hole pressure limits are crucial well-control parameters in UHS systems. The minimum BHP limit is determined through techno-economic factors considering surface compression requirements. On the other hand, the maximum BHP limit is established based on rock mechanics and fracture gradient to ensure reservoir integrity and stability. This paper contributes to a comprehensive framework for optimizing Underground Hydrogen Storage systems by proposing novel insights and key strategies, that can play a role in the viability and scalability of hydrogen as an energy storage solution in the transition to a sustainable energy future.