Effects of reservoir interlayers on hydrogen migration and distribution in underground hydrogen storage

With the rapid expansion of renewable energy deployment, underground hydrogen storage (UHS) has emerged as a promising large-scale storage option to smooth seasonal fluctuations in electricity supply. However, current geological assessments for UHS primarily focus on reservoir properties such as porosity and permeability, while overlooking the influence of interlayers. To address this research gap, this study systematically investigates how interlayer characteristics, including permeability, thickness, and geometry, affect hydrogen recovery efficiency and the extent of unrecoverable hydrogen. Numerical simulations were conducted using OpenGoSim (OGS) software, beginning with a box model and extending to a realistic geological model based on the Ahuroa gas storage site. Simulation results reveal that, under fully perforated conditions, lower interlayer permeability impedes upward hydrogen migration, thereby reducing the impact of gravity override and enhancing hydrogen recovery efficiency. With decreasing interlayer permeability, hydrogen transport into the interlayer shifts from advection-dominated transport to diffusion-dominated transport, resulting in greater hydrogen volume than predicted by a model that neglects molecular diffusion. The study further demonstrates that optimizing well configuration should consider interlayer properties to maximize recovery efficiency. Consistency between the box model and the realistic geological model supports the generality of the findings. By integrating interlayer characteristics into site evaluation, this work enhances the accuracy of hydrogen recovery efficiency evaluation and advances UHS assessment. • The impact of interlayers on hydrogen recovery efficiency in UHS is systematically evaluated. • Interlayer permeability, thickness, and pinch-out extent affect hydrogen migration and recovery efficiency. • Molecular diffusion effects on hydrogen migration in gas-saturated, low-permeability interlayers should not be neglected. • Well configuration should be optimized based on interlayer characteristics to enhance hydrogen recovery efficiency.