Experimental data in shale fractures assessing the biogeochemical conditions that affect sulfate reducing bacterial growth, distribution, and activity for sulfate reduction is sparse, and this has limited our ability to evaluate predictive models for assessing potential impacts. In this work, we developed a shale-based microfluidic platform.  It contains a single 250 micrometer-wide fracture created from a natural shale sample, equipped with two inlets and one outlet. Organic acids representing hydrocarbon fermentation products and electron donor were fed into one inlet, while sulfate as the electron acceptor was fed into the other inlet.  These solutes mixed along the fracture centerline to promote biomass growth and sulfate reduction. Biomass growth was quantified at different influent sulfate flux rates using transmitted brightfield microscopy, and sulfide production was quantified using a novel effluent zinc trap. Experimental results revealed that biomass grew on the shale fracture walls and in the channel, and biomass growth on shale fracture walls extended further downgradient with increasing influent sulfate flux rate. A reactive transport model was developed to simulate these results, and a specific sulfate reduction rate was obtained and compared to literature values to assess representative rates for predictive modeling.

Evaluation of sulfate reduction rates by biofilm on shale fracture walls of a microfluidic reactor

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.