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STULTS, John ¹

¹ CU Boulder

The last decade of oil and gas exploration in the United States has been characterized by a sharp increase in the amount of oil and gas acquired from low-permeability shale formations. These low-permeability formations are non-traditional oil and gas reservoirs, which require hydraulic fracturing to stimulate oil and gas production. Many current and planned hydraulic fracturing operations now encroach on urban and peri-urban areas, raising alarm over the potential groundwater contamination threat posed by chemicals in hydraulic fracturing fluids. The purpose of this study was to develop a risk analysis metric that could be cross-referenced with hydraulic fracturing data to evaluate spatio-temporal trends related to the safety of chemicals used in hydraulic fracturing. A risk analysis metric was developed using available transport, persistence, and toxicity data on chemicals found in hydraulic fracturing fluids. Chemicals with available data were given a “combined risk score” based on their transport time, persistence, and toxicity data. Our team compiled PDF and machine-readable data from FracFocus, the largest publicly available database on hydraulic fracturing, into one machine readable database. The FracFocus data used in this study spanned from January 1st, 2011 through data posted as of February 22nd, 2018, and contained 116231 hydraulic fracturing job records. there were 302 chemicals found in FracFocus with available combined risk score data. Every chemical used in the 116,231 hydraulic fracturing jobs was evaluated, and each job was given a “job combined risk score” based on combined risk score of chemicals with available risk used in the job. Out of the 116,231 jobs analyzed, 106,691 (91.8%) had available combined risk score data. There is quasi-significant trend observed of increasing job combined risk scores from 2011 through the end of 2016. There are several spatial regions (i.e. states, sedimentary basins, or shale plays) which have significantly higher job combined risk scores, and several spatial regions which demonstrate significant trend toward increasing job combined risk scores over time. This integrated risk and data analysis approach to evaluating the potential groundwater threat of hydraulic fracturing chemicals is one of the largest and most comprehensive analysis of hydraulic fracturing chemicals ever attempted. Overall, this analysis framework is a valuable tool for oil and gas industry professionals and regulators to assess trends related to the use of hydraulic fracturing fluid chemicals on national and regional scales.