Microbiological Aspects of Hydrogen Storage in Porous Underground Storages

Based on extensive experiences from previous case studies, laboratory analyses on several gas caverns and porous underground gas storages as well as many years of research it is known that most potential H2-underground storages are already colonized with microorganisms which can consume hydrogen as sole energy source. Particularly relevant to a feed-in of hydrogen are methanogenic Archaea and especially sulfate-reducing Prokaryotes (SRP). In addition to chemical changes in the formation water and blockage of the pore space, SRP leads in particular to a formation of hydrogen sulphide (H2S). Because of the dominance and resilience of SRP to adverse living conditions (tolerance to high pH, temperature, mineralization), we find this group of microorganisms in numerous gas storages as well as in oil and gas reservoirs. In contrast to caverns, pore reservoirs offer favorable conditions for microbial growth due, among other things, to large growth surfaces, pressure-driven flow processes, complex minerals (carbonate, sulfate, etc.) and often low mineralization. Our many years of experience suggest that feeding hydrogen into microbially colonized underground pore reservoirs will inevitably lead to stimulation of the microbial population. Hence, the foreseeable microbial risks of hydrogen injection into porous underground storages must therefore be discussed.