The unconventional oil and gas boom, facilitated by advances in horizontal drilling and hydraulic fracturing, has raised concerns about the potential contamination of groundwater resources. The objective of this study was to evaluate polypropylene glycol surfactants (PPGs) and their degradation products as potential indicator compounds for hydraulic fracturing fluids under conditions simulating a surface spill to shallow groundwater. Microcosms were constructed using alluvial aquifer sediments and a 14-day flowback water collected directly from the separator tank of a Denver-Julesburg Basin production well mixed at a 1:10 ratio with a synthetic groundwater. Ultrahigh-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UHPLC/QTOF-MS) was used to separate and identify the PPGs and their degradation products. The PPGs were 30-40% degraded in 4 days under oxic conditions and no additional removal was observed under anoxic conditions. PPG carboxylates (PPG-Cs) were identified for the first time in flowback water samples and are known to be products of PPG degradation. Accurate mass with MS-MS results were used to identify the degradates. The MS-MS analysis showed that the PPG surfactants undergo fragmentation by loss of the carboxyl group followed by sequential losses of 58 mass units, which correspond to the polypropylene group. The identifications were unequivocal. The PPG-Cs were not detected at the initial time point, and their formation was correlated with the observed removal of the PPGs. Interestingly, only one end of the PPG undergoes carboxylation, which will be explained in detail. These results suggest that both the relatively persistent PPGs and the PPG-C degradation products may have applications as indicator compounds of oil- and gas-related wastewaters accidentally released to shallow groundwater, particularly under anoxic conditions.

Polypropylene glycol surfactants and their degradation products as potential indicator compounds for shallow groundwater impacted by hydraulic fracturing fluids

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.