MICROBIOMES OF UNCONVENTIONAL OIL AND GAS WELLS IN WYOMING

Unconventional drilling has revolutionized oil and natural gas production, but little is understood about the downhole microbial ecosystems encountered. MiSeq 16S rDNA sequencing was performed on produced waters collected at the liquid-gas separator of 6 wells in the Powder River Basin, 8 wells in the Green River Basin, and 4 wells in the Wind River Basin in Wyoming. Well depths range from approximately 7,000 ft to approximately 15,000 ft. Microbial DNA isolated from unconventional wells in the Powder River Basin was enriched with DNA from Thermovirga, Anaerobaculum, and Desulfomicrobium, while Thermoanaerobacter, Pseudomonas, and Planococcus were enriched in samples collected from Green River Basin wells. Microbiomes of wells in the Wind River Basin varied more, but Marinobacterium, Pseudomonas, Acetobacterium, and Brevundimonas were prevalent in these samples. This data contrasts sharply with reports of microbial communities in unconventional wells of the Marcellus, Utica, and Antrim shales.

Among the 18 wells that were analyzed, no single microbe was detected in all samples. While the microbiomes of the examined wells differ significantly, they best correlate when wells are grouped by basin in which they are located. Comparative analysis revealed that samples collected in the Powder River Basin are unlike those collected in the Green River and Wind River Basins; however, unconventional drilling in the Powder River Basin is used to access conventional reservoirs. Ongoing work includes correlating microbes present in a samples with the measured salinity, pH, and concentration of inorganic ions in the produced waters from which the DNA was isolated to better understand how these microbial communities survive in these extreme environments.