Jena Choi, “Chemical and Optical Characterization of Produced Water from the Permian Basin Oil Field”
Mentor: Laodong Guo, Freshwater Sciences
Poster #105

Oil field produced water is generally a mixture of petroleum, dissolved organic matter, rare metals, and contaminants. For recycling and metal recovery, knowledge about the chemical matrix of produced water is indispensable. Forty samples were collected from the largest US petroleum basin and analyzed for major ions, dissolved organic carbon (DOC), chromophoric and fluorescence dissolved organic matter (CDOM and FDOM). Concentrations of major ions (mg/L) ranged from 4,101-63,953(average 17,490±14,338) for Na⁺, 920.4-11,334.9 (4,054±2300) for Ca⁺², 57.6-719.2 (403±184) for K⁺, and 128 -1850 (689±421) for Mg⁺², surpassing those of Na⁺ and Ca⁺² in seawater and similar for K⁺ and Mg⁺². Molar ratios of Mg⁺²/Ca⁺² ranged from 0.21-0.56 (average 0.28±0.06), which are much lower than those in contemporary seawater (4.9-5.3). Concentrations of DOC ranged from 7.6-96.5 ppm (average of 38.3 ± 23.3 ppm), while CDOM (absorption coefficient at 254 nm, a₂₅₄) varied from 59.72-480.1 m^-1 with an average of 156.2± 97.1 m^-1. There exists no significant correlation between DOC and CDOM, indicating that these produced water contained different sourced DOM. Specific-UV-Absorbance at 254 nm (SUVA₂₅₄), an indicator of aromaticity, ranged from 0.0027-0.0933 L/mg-C/m, with an average of 0.024±0.019L/mg-C/m. Spectral slope (S_275-295), inversely correlated with molecular weight, varied from 0.0013to 0.0604 nm^-1. Parallel-factor analysis (PARAFAC) on fluorescence-EEM identified 4 major fluorescent components: three protein-like or oil-like (C1, C3, C4) and one terrestrial humic-like (C2). Fluorescence-index (FIX), humification-index (HIX), and biological-index (BIX) varied widely, indicating diverse DOM sources (terrestrial, microbial and oil), consistent with the poor correlation observed between DOC and CDOM. Our results provide an improved understanding of sources and properties of oil field produced water and science base for better disposal, recycling, and metal recovery.

.