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 %.