Impact of specific surface area on anaerobic microbial hydrogen consumption by a sulfate reducer: A sand pack study

Subsurface hydrogen storage in porous media exposes hydrogen to native anaerobic microbes, potentially reducing hydrogen storage efficiency and recovery predictability through microbial consumption. This study investigated how specific surface area (SSA) affects hydrogen consumption by a sulfate-reducing bacterium Oleidesulfovibrio alaskensis G20. Experiments used sand packs simulating sandstone reservoirs with grain sizes and SSAs of (0.25 mm, 12 mm −1 ), (0.5 mm, 6 mm −1 ), and (1 mm, 3 mm −1 ) at 37 °C and 1.45 bara. Larger surface areas yielded higher initial hydrogen consumption rates and shorter consumption intervals, a trend consistent with hydrogen dissolution in brine. Initially, fine and medium-grained packs showed low consumption rates, peaking at 2.38 and 1.79 μmol H 2 /hr/mL, lasting 16 and 22 h respectively. The coarse-grained pack reached its peak consumption (2.37 ± 0.01 μmol H 2 /hr/mL) immediately post shut-in, declining to zero after 44 h. Despite elevated initial consumption rates, microbial hydrogen consumption in fine-grained packs was constrained by increased local brine alkalinity (average final pH = 8.0), resulting in only 22–29 % utilization of the potential hydrogen relative to the initial sulfate concentration. Medium-grained packs, with moderate hydrogen dissolution and consumption rates, showed the highest hydrogen loss, consuming 92–97 % of potential hydrogen and reaching a limiting pH of 8.5. The results highlight that specific surface area (SSA) significantly impacts microbial hydrogen consumption rates in porous media, providing insights crucial for microbial risk assessment and improved hydrogen recovery predictions from subsurface porous media storage sites. • Core-scale sand-pack experiments quantifying anaerobic microbial hydrogen consumption. • Microbial hydrogen consumption is influenced by the specific surface area of the sand pack. • Higher consumption rates shorten consumption intervals and net hydrogen loss declines over successive cycles. • Increased surface area enhances hydrogen dissolution into the brine phase. • Consumption constrained by local brine pH, sulfate availability, and effective hydrogen diffusion coefficient.