Methanogenic conversion of hydrogen to methane in reservoir rocks: An experimental study of microbial activity in water-filled pore space

Abstract

Underground hydrogen storage can lead to the activation of methanogenic Archaea, demanding to quantify microbial activities within the pore space to evaluate potential hydrogen conversion rates. This study presents a method to determine microbial activities within various water-saturated reservoir rocks, inoculated media containing sand particles and rock fragments as well as bulk solution, by monitoring pressure and gas composition. Measured activities in water-saturated rock specimens with identical bulk volumes varied between 0.15 and 1.28 mM H2/h correlating with pore volume. Additionally, the results reveal that activities within intact rocks are 8–10 times higher than in corresponding bulk solutions. This observation demonstrates that the surface area available for microorganism colonization is another potential factor controlling microbial activity when the substance amount is held constant. This notion is supported by activities measured in inoculated media containing sand particles and rock fragments, as well as in rocks with similar pore volumes.