Microbial H₂ Consumption by a Formation Fluid from a Natural Gas Field at High-Pressure Conditions Relevant for...

Underground hydrogen storage (UHS) has been proposed as one option for storage of excess energy from renewable sources. Depleted gas reservoirs appear suitable, but at the same time, they may be environments with potentially high microbial abundances and activities. Hydrogen (H₂) is one of the most energetic substrates in such environments, and many microorganisms are able to oxidize H₂, potentially leading to loss of H₂ or other unwanted reactions like production of, e.g., H₂S, clogging, or corrosion. This study addressed the potential of H₂ consumption by naturally abundant microorganisms in formation fluid from a gas field at near in situ pressure and temperature conditions. Microbial H₂ consumption was evident at ambient and 100 bar and tolerated pressure variations reflecting cycles of H₂ storage. Temperature strongly influenced the activity with higher activity at 30 °C but lower activity at 60 °C. The activity was sulfate-dependent, and sulfide was produced. The microbial community composition changed during H₂ consumption with an increase in sulfate-reducing prokaryotes (SRP). Thus, the presence of an SRP-containing, H₂-consuming microbial community with activity at UHS-relevant pressure and temperature conditions was shown and should be taken into account when planning UHS at this and other sites.