High volume hydraulic fracturing requires millions of gallons of hydraulic fracturing fluid (HFF) for the development of gas wells. HFF contains up to 2% chemical additives, prompting concerns about water quality impacts. Whereas over one thousand chemicals have been disclosed as HFF additives, a large number remain proprietary and the chemical structures of transformation products are mostly unknown. These knowledge gaps complicate the development of water quality monitoring studies.  In this research, we developed a non-target chemical screening approach and applied it to HFF samples to elucidate the structures of unknown chemical constituents. The method was developed and validated using a synthetic mix of HFF additives. Samples of HFF from two natural gas wells in the Marcellus Shale Play were then diluted so that the total concentration of chemical additives in the solution ranged from roughly 100 µg/L to 10 mg/L. The samples were processed to remove inorganic matrix and analyzed by means of high-resolution mass spectrometry. We then developed a data-processing workflow based on the differential abundance of mass features measured among the dilutions. This analysis yielded a list of accurate masses of chemical constituents in the HFF samples. Accurate masses were aggregated to identify the neutral mass of specific chemical constituents and were assigned molecular formulae based on the accurate mass and isotopic patterns. Chemical structures were then assigned based on database searching and/or analysis of other analytical data such as tandem mass spectra.  To date, our approach has allowed us to identify a number of homologous series of surfactants, including individual constituents that were not disclosed in the respective FracFocus reports. We have also identified biocides and apparent biocide transformation products. This method offers a new approach for analysis of HFF and associated wastewaters, and could be applied to detect multiple classes of additives and degradation products.

Non-target screening for polar to semi-polar organic compounds in hydraulic fracturing fluids

252nd National Meeting (2016)

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