Hydraulically Fractured Shale Fluids Raw sequence reads

Microbial activity associated with produced water from hydraulic fracturing can lead to gas souring and corrosion of carbon-steel equipment. While the microbial ecology of such waters has been well documented, the roles of the prevalent microorganisms in corrosion remain underexplored. We examined the microbial ecology of produced water and the associated corrosion problems occurring in a shale gas facility in the Barnett formation. The microbial community was mainly composed of halophilic, sulfidogenic bacteria within the Order Halanaerobiales, which reflected the geochemical conditions of highly saline water (11.7% Cl-) containing sulfur species (S2O32-, SO42- and HS-). A halophilic bacterium was subsequently isolated and identified as Halanaerobium sp. DL-01. The isolate could degrade guar gum (0.5%), a polysaccharide polymer used in fracture fluids, to produce acetate (11.8±0.8 mM) in a 10% NaCl medium at 37°C. The strain could also couple guar gum oxidation with thiosulfate reduction, producing sulfide (7.1±0.3 mM) and roughly twice the amount of acetate (27.3±0.7 mM) than under fermentative growth conditions. Unexpectedly, the degree of carbon-steel coupon dissolution in Halanaerobium incubations was less than sterile controls. Abiotic experiments revealed that the equivalent amount of sulfide and acetate produced in Halanaerobium cultures caused more pronounced pitting corrosion than the corresponding incubations without these components. Furthermore, triclosan and quaternary ammonium compounds were found to be efficient biocides against strain DL-01. Collectively, our findings suggest that sulfide and acetate produced during anaerobic polysaccharide biodegradation by subsurface microorganisms might be transported in pipelines and cause pitting corrosion in other locations where microbial activity might be minimal or absent due to various control measures.