PNNL

Abstract

Hydraulic fracturing of black shale formations has greatly increased United States oil and natural gas recovery. However, the accumulation of biomass in subsurface reservoirs and pipelines is detrimental because of possible well souring, microbially induced corrosion, and pore clogging. Temporal sampling of produced ?uids from a well in the Utica Shale revealed the dominance of Halanaerobium strains within the in situ microbial community and the potential for these microor- ganisms to catalyze thiosulfate-dependent sul?dogenesis. From these ?eld data, we investigated biogenic sul?de production catalyzed by a Halanaerobium strain iso- lated from the produced ?uids using proteogenomics and laboratory growth experi- ments. Analysis of Halanaerobium isolate genomes and reconstructed genomes from metagenomic data sets revealed the conserved presence of rhodanese-like proteins and anaerobic sul?te reductase complexes capable of converting thiosulfate to sul- ?de. Shotgun proteomics measurements using a Halanaerobium isolate veri?ed that these proteins were more abundant when thiosulfate was present in the growth medium, and culture-based assays identi?ed thiosulfate-dependent sul?de produc- tion by the same isolate. Increased production of sul?de and organic acids during the stationary growth phase suggests that fermentative Halanaerobium uses thiosul- fate to remove excess reductant. These ?ndings emphasize the potential detrimental effects that could arise from thiosulfate-reducing microorganisms in hydraulically fractured shales, which are undetected by current industry-wide corrosion diagnos- tics.