MICROBIAL COMMUNITIES IN OIL AND GAS PRODUCED WATER OF THE POWDER RIVER AND GREEN RIVER BASINS IN WYOMING

Hydraulic fracturing has revolutionized natural gas production, but little is understood about the downhole microbial ecosystems encountered. Illumina MiSeq 16S rRNA sequencing has been performed on waters collected from Cretaceous and Paleocene hydraulically fractured wells in Wyoming. We compared samples collected from the water-gas separator of each well for six horizontally drilled oil wells in the Powder River Basin (PRB) and five vertically drilled wells gas wells in the Greater Green River Basin (GRB) in Wyoming, and identification of bacteria and archaea reveal the presence of several microbes. Well depths ranged from approximately 10,000ft to 12,500ft in the Powder River Basin and approximately 9,500ft to 11,500ft in the Green River Basin. Analytical results characterize a microbial framework with respect to biocides used during fracturing and production and the inorganic chemistry, including pH, salts, and metals naturally present in the groundwater.

Over 500 unique 16S rRNA sequences have been identified through this analysis. Preliminary results identify several microbial families including: Clostridiales, Thermoanaerobacterales, Synergistales, Alteromonadales, and Thermotogales. Of the 6 sampled oil wells in the Powder River Basin, 19 microbes were identified as present in all 6 samples in varying amounts, including Pseudomonas, Thermoanaerobacter, and Acetobacterium. Analysis revealed that 16 microbes were identified in all 5 of the samples collected from the Green River Basin, including Anaerobaculum, Thermovirga, and an unclassified Clostridiaceae. Only one microbe, an unclassified species of Thermoanaerobacter, was detected in all tested samples.

In general, the microbes present correlate with formation temperature and salinity. We found many amplified 16S sequences did not match a sequence in databases, indicating the large number yet identified and classified microbes present in these exotic environments. Ongoing work includes matching similar though unidentified 16S sequences present in multiple samples and correlating microbial populations across wells to understand better the microbial communities present at these environmental conditions.