As Bakken Shale region has become of the nation’s most important oil and gas producers, produced water volumes from this reservoir have steadily increased. Currently, a single Bakken wells generates more than 3 million gallons of produced water throughout its lifetime. Understanding the microbial ecology and chemical composition of this produced water is of high significance for water management, as utilizing the wrong strategy can result in the release of hazardous materials such as brines, metals, and fracturing fluid additives, an increased biocide resistance, and/or promotion of acid and sulfide production, and biofilm formation. However very little data is currently available on the chemistry and microbial communities of produced waters from the Bakken Shale region. The goal of this study was to better define the microbiology and chemistry of Bakken shale produced water through the most comprehensive evaluation of Bakken Shale produced water samples to date. We evaluated produced water samples from 17 Bakken and Three Forks formation wells at 4 sampling time points across a 6 month period (October 2014 to March 2015). Chemical analysis revealed produced water samples from all locations and at all time points were characterized by high TDS concentrations (220,000 mg/L – 350,000 mg/L). Microbial abundances were found to be very low across all samples and 3 to 4 orders of magnitude below those observed for produced waters from other unconventional resource regions. Microbial community structure analysis using 16S rRNA sequencing suggested produced water samples to be dominated by the order Bacillales, Halanaerobiales, and Pseudomonadales. The taxa Halanaerobiales was particularly abundant in October samples, while the order Bacillales was more abundant in November, January and March samples, a shift likely due to a drop in ambient temperature (8oC to -2oC). Furthermore we identified sequences affiliated with the orders Oceanospirriales, Campylobacterales, Actinomycetales, Lactobacillales, Clostridiales and Bacteroidales at abundances of 10% or greater, and sequences associated with the classical sulfate reducers Desulfovibrionales and Desulfomonadales at abundances between 1% and 2%. Data from this study extends the current knowledge of chemistry and microbiology of hydraulic fracturing produced water to include the Bakken Shale, and will contribute to the development of better produced water management strategies in the future.

Microbiological evaluation of hydraulic fracturing produced water from 17 Bakken Wells across a 6 month time frame

253rd National Meeting (2017)

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