Numerical simulation of cyclic hydrogen storage in depleted gas reservoirs: considering microbial growth and hydrogen consumption

The physical properties of H₂ and the H₂-consuming effects of microorganisms present challenges to efficient H₂ storage. This study established a comprehensive mathematical model considering the physical properties of H₂ and the mechanisms of microbial growth, combined with mass conservation, to form a numerical simulation method. The effects of H₂ relative permeability hysteresis, dissolution, diffusion, and adsorption, as well as the impact of microbial fate and competition mechanisms are investigated. Results show 21.77 % of H₂ trapped, forming three unrecoverable H₂ pockets near the well zone, lower structural positions of the gas reservoir, and the surrounding areas of the H₂ chamber, over three H₂ storage cycles. The coexistence of methanogens and homoacetogens is hindered by pH selection, while the production of H₂S inhibits the growth of methanogens. Methanogen consumed 5.36 % of H₂, with competition between sulfate-reducing bacteria and methanogens resulting in the consumption of 9.21 % of H₂. Microorganisms aggregate at the unrecoverable H₂ pockets, where methanogens and sulfate-reducing bacteria growth result in reservoir blockage, while homoacetogens growth has minimal impact on reservoir blockage. With active microorganisms, the H₂ recovery rate in depleted gas reservoirs ranges from 55.61 % to 61.09 %, with a H₂ recovery purity of 74.94 %–77.82 %.