The potential of hydrogen storage in depleted unconventional gas reservoirs: A multiscale modeling study

Subsurface energy storage in depleted petroleum reservoirs is a promising technique to balance and optimize the utilization of energy resources. In this work, we numerically explore the possibility of storing excessive hydrogen gas in depleted unconventional gas reservoirs. Our study is a multiscale analysis. From the molecular (pore) scale, we inves-tigate the thermodynamics and transport mechanism of the hydrogen gas in the nano-pores of the unconventional reservoirs. Then based on the results of the pore scale, we conduct reservoir-scale simulations to quantitatively investigate the preferred cycling pressure, the effective fraction of cushion gas and the amount of storage capacity of un-conventional reservoirs. We have discovered that, compared to conventional gas reser-voirs, hydrogen stored in unconventional reservoirs maintains higher purity because of the differential adsorption effect of the nanopores. This feature makes depleted unconven-tional gas reservoirs appealing candidates for underground storage of the hydrogen gas.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.