COMPARATIVE ANALYSIS OF MICROBIAL COMMUNITIES IN TWO SIMILAR UNCONVENTIONAL OIL WELLS IN THE POWDER RIVER BASIN, WYOMING

DNA was isolated from produced waters from two unconventional oil wells in the Powder River Basin in northeast Wyoming, and Illumina MiSeq 16S rDNA sequencing was used to identify bacteria and archaea in these samples. Well PRB-18 was drilled to 12,305 ft, and well PRB-19 is 12,339 ft deep. Characterization of the produced water (pH, conductivity, TDS, alkalinity, SAR, concentrations of major ions, total sulfur, sulfate, and phosphate) from which the DNA was isolated, as well as the similar geology, indicate that the detected microbes originated from similar deep subsurface environments. Comparison of DNA sequences in each sample revealed that 99% of sequences in PRB-18 and 86% in PRB-19 are common to both samples. Interestingly, the relative abundance of those sequences differs significantly, indicating different microbial community structures in the two well environments. PRB-18 was dominated by Thermovirga (58%), followed by Anaerobaculum (15%) and Desulfomicrobium (12%). The relative abundance of DNA sequences collected from PRB-19 reveals a more diverse community, which includes Thermosipho (23%), Methermicoccus (13%), Thermovirga (12%), Marinobacter (12%), novel sequences in the order Clostridiales (8%), and Desulfomicrobium (6%). These results illustrate the variance in microbial communities that can exist in very similar environments, and highlights the current limitations on predicting microbial community structure on the basis of environmental and well data.