Underground hydrogen storage with cushion gas and moisture: A molecular simulation

Hydrogen energy has been positioned as a viable substitute for traditional fuels in addressing global warming challenges. Depleted gas reservoirs have emerged as a practical geological solution for large-scale underground hydrogen storage. We systematically investigated the effect of moisture, cushion gas (CH 4 ), pressure, temperature, and pore wettability on the impact of H 2 storage and migration. The results reveal that pore wettability affects the occurrence state of water, which in turn influences the distribution of H 2 and CH 4 . In pores without H 2 O, gas distribution is independent of wettability. The presence of water and cushion gas in pores markedly inhibits hydrogen diffusion, albeit at the cost of a partial reduction in storage capacity. Moreover, increasing pressure and reducing temperature could both enhance the storage and hinder the diffusion behavior of H 2 , regardless of pore hydrophilicity or hydrophobicity. This investigation yields novel perspectives on the nanoscale behavior of H 2 in geological storage.