Comparative study of three H2 geological storages in deep aquifers simulated in high-pressure reactors

Abstract

Massive storage of dihydrogen (H2) in underground geological storage (UGSs) will be necessary to meet future H2 production ambitions. Such storage in deep aquifers was simulated in a high-pressure reactor, and the evolution of the 3 phases (natural gas/H2, formation water and rock) with autochthonous microorganisms was monitored over several weeks. These results show that methanogens do not necessarily dominate the community, but that sulfate-reducing activity and formate bioproduction are systematically present. The experimental data were fed into a biochemical model in PHREEQC to better understand the interplay between the phenomena observed. In particular, it was shown that the microbial activities associated with H2 consumption led to alkalinisation, which could explain, at least in part, the slower rate at which H2 disappeared, even if sufficient CO2 and sulfate remained in the system. Combined with a supposed local nutrient depletion, these results are encouraging for H2 storage in deep aquifers.