title: Identification of polypropylene glycols and polyethylene glycol carboxylates in flowback and produced water from hydraulic fracturing.
abstract: The purpose of the study was to separate and identify the unknown surfactants present in flowback and produced water from oil and gas wells in the Denver-Julesburg Basin (Niobrara Formation) in Weld County, Colorado, USA. Weld County has been drilled extensively during the last five years for oil and gas between 7000-8000 feet below land-surface. Polypropylene glycols (PPGs) and polyethylene glycols carboxylates (PEG-Cs) were found for the first time in these flowback and produced water samples. These ethoxylated surfactants may be used as friction reducers, clay stabilizers, and surfactants. Ultrahigh-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UHPLC/QTOF-MS) was used to separate and identify the different classes of PPGs, PEG-Cs, and their isomers. The Kendrick mass scale was applied along with mass spectrometry/mass spectrometry (MS-MS) with accurate mass for rapid and unequivocal identification. The PPGs and their isomers occur at the ppm concentration range and may be useful as "fingerprints" of hydraulic-fracturing. Comparing these detections to the compounds used in the fracturing process from FracFocus 3.0 (https://fracfocus.org), it appears that both PPGs and polyethylene glycols (PEGs) are commonly named as additives, but the PEG-Cs have not been reported. The PEG-Cs may be trace impurities or degradation products of PEGs.
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder, CO 80303 USA. Electronic address: michael.thurman@colorado.edu.
authors.forename: E Michael
authors.initials: EM
authors.lastname: Thurman
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder, CO 80303 USA. Electronic address: imma.ferrer@colorado.edu.
authors.forename: Imma
authors.initials: I
authors.lastname: Ferrer
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder, CO 80303 USA. Electronic address: james.rosenblum@colorado.edu.
authors.forename: James
authors.initials: J
authors.lastname: Rosenblum
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder, CO 80303 USA. Electronic address: karl.linden@colorado.edu.
authors.forename: Karl
authors.initials: K
authors.lastname: Linden
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder, CO 80303 USA. Electronic address: joseph.ryan@colorado.edu.
authors.forename: Joseph N
authors.initials: JN
authors.lastname: Ryan
keywords: Accurate mass; Hydraulic fracturing; LC/QTOF-MS; Polypropylene glycols