Assessing Hydrogen Leakage in Underground Hydrogen Storage: Insights from Parametric Analysis

Hydrogen plays a vital role in renewable energy systems and has a significant environmental impact. Storing hydrogen in underground geological formations offers an efficient and safe solution to balance production and consumption. However, due to hydrogen's unique properties, there is a risk of leakage through the caprock of underground aquifers, potentially causing serious issues such as groundwater contamination, reduced storage efficiency, and explosion hazards. This study employs numerical simulations to investigate hydrogen leakage from caprock during underground storage, focusing on key parameters. These parameters include injection and production rates, cycle duration, hydrogen molecular diffusion, aquifer pressure, injection and production depths, well types, aquifer dip angle, caprock permeability, and capillary entry pressure. By examining these factors, the study provides an in-depth comprehensive analysis of hydrogen leakage from aquifers, addressing a critical gap in existing research. The results indicate that a significant amount of the total injected hydrogen leaks into the caprock after eight years of injection and storage cycles. This leakage can have significant environmental and economic impacts. The study also reveals that caprock permeability is crucial in influencing hydrogen leakage with higher permeability leading to increased leakage rates. Moreover, vertical caprock permeability has a more pronounced effect on leakage rates than horizontal permeability. Additionally, factors such as aquifer pressure, aquifer dip angle, injection and production depths, and hydrogen injection duration contribute to a higher hydrogen leakage from the caprock. The findings underscore the importance of carefully selecting underground hydrogen storage sites to mitigate the potential risks of hydrogen leakage.