Characterization of Organic Matter in Water from Oil and Gas Wells Hydraulically Fractured with Recycled Water.

Liquid chromatography quadrupole time-of-flight mass spectrometry was performed to understand how frac fluid with recycled water (RWA) and frac fluid with fresh water (FWA) compare when subjected to downhole temperature and oxidation conditions. Ethylene oxide and propylated glycol functional units were quantified from both RWA and FWA. Qualitative analysis was performed using Agilent qualitative analysis software B.06.00 based on the exact mass of the chemical compound. Acetone, aldol, alkoxylated phenol formaldehyde resin, diethylbenzene, dipropylene glycol, d-Limonene, ether salt, ethylbenzene, n-dodecyl-2-pyrrolidone, dodecylbenzenesulfonate isopropanolamine, polyethylene glycol, and triethylene glycol were detected in FWA and RWA samples. In the van Krevelen diagram, FWA and RWA show a low degree of oxidation and highly saturated organic compounds. Kendrick mass defect (KMD) analysis was applied using ethylene oxide and propylated glycol units. KMD analysis based on ethylene oxide was scattered between 0 and 0.1, while some KMD analyses based on the propylated glycol are close to 1. FWA had an average carbon number of 32.3 and double bond equivalent (DBE) of 9.8 while RWA had average carbon number of 31.5 and DBE of 9.5. RWA contained predominantly C21-C40 compounds, while FWA had a higher concentration in the over C41 range.