ORGANIC COMPOUND CHARACTERIZATION OF HYDRAULIC FRACTURING FLOWBACK WATERS THROUGHOUT THE FRACTURING PROCESS

A typical horizontal fracturing operation requires about 15,000 m³ (4 million gallons) of potable water. After the fracturing event is complete, injection waters return to the surface as flowback and produced water. These waters are commonly transported off site and disposed of using deep well injection, thereby removing them from the hydrologic cycle. In many regions, this water has the potential to be a valuable resource with proper treatment. Recently, there has been advancement in water treatment methods for flowback and produced waters. However, because flowback waters have unique matrices and contain non-traditional pollutants such as polymers, treatment becomes costly and inefficient. Due to this, there is a need to better characterize flowback and produced waters through time to optimize treatment efficiencies.

This study uses modern liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) and gas chromatography tandem mass spectrometry (GC-MS/MS) characterize these matrices. A non-target analysis method was used to discover unidentified compounds’ accurate mass. High resolution mass spectrometry data (HRMS) was then screened using a variety of algorithms for isotopic patterns, adduct compounds, and homologue series. Isotopic patterns and adduct information were then related to the undefined compounds, which was then combined with homologue series information to identify unknown compounds. Using this approach, we identified several new classes of nitrogen containing surfactants previously unreported in the literature, including alkylamine surfactants (C₈H₁₉N-C₂₅H₅₃N) and phenyl alkyl amines with odd number carbon chains (C₁₅H₂₅N-C₂₇H₄₉N). We also identified polyethylene glycol O₆ alkyl ethers that have been identified in previous research. A main focus of this research was to better understand when specific compounds of concern are returning up hole; this information is crucial when optimizing treatment methods. Understanding the compounds that are present in flowback and produced waters will also be useful when identifying residual organic compounds that are not removed during the traditional treatment process.