Biogeochemical Assessment of Short-Term Hydrogen Storage in Methane Reservoirs with Field Sample Characterization and...

Hydrogen is a valuable commodity due to its high energy density and properties as a flexible energy carrier. It is possible to store hydrogen by blending it with methane and utilizing existing natural gas infrastructure. However, adapting current methane storage strategies to withstand the expected biogeochemical processes caused by H₂ injection has not been fully explored. In this study, a series of experiments were designed to identify potential geochemical and microbial challenges of storing hydrogen/methane gas blends in existing methane reservoirs. First, fluid samples were collected from two methane reservoirs located in the western United States. The geochemical composition, microbial taxonomy, and metabolic potential of each fluid sample were characterized by utilizing ion chromatography (IC), inductively coupled plasma optical emission spectroscopy (ICP-OES), a Total Organic Carbon (TOC) analyzer, 16S rRNA gene amplicon sequencing, and metagenomic sequencing. Next, fluid samples from one field site (Site 2) were used to complete a series of short-term reactor experiments at reservoir conditions (80 °C and ∼1000 psi) for natural gas (100% CH₄) and hydrogen blend (80% CH₄/20% H₂) storage environments. Both biotic and abiotic (sterilized) measurements were conducted to accurately understand and decouple abiotic and microbially driven processes, with the goal of linking these processes to storage impacts. Overall, the two reservoirs had a high, but variable, total dissolved solids (TDS) concentration, with various organic acids including acetate and propionate. The field sample was characterized by a diverse microbial community with the metabolic capacity for sulfur reduction, iron reduction, and acetogenesis. Across these reactors, there was minimal change in the fluid geochemistry and a minimal (0-5%) decrease of hydrogen gas during the initial storage event (days 1-3). This work contributes to the understanding of the complexities of hydrogen storage and demonstrates the need for additional research.