| Abstract |
The United States is estimated to have generated 890 billion gallons of produced water during oil and gas operations in the 2012 calendar year (Veil, 2015). Produced water is typically saline, contains dissolved materials of value, and is of elevated temperature. In this work we examine a subset of the water and rock data generated by University of Wyoming, Idaho National Labs, and U.S. Geological Survey under their project DE-EE0007603. The water data we consider describes REE concentration and geochemistry of produced water in the Wind River Basin and the Powder River Basin of Wyoming. The rock data we consider describes the REE concentration and whole-rock geochemical data of the reservoir host rocks. We apply the Wyoming Basin Produced Waters (WBPW, Nye et al., 2018) and North American Shale Composite (NASC, Gromet et al., 1984) to identify significant features in these waters and rocks. Two case-studies show the benefits of this combined approach. In the first, gadolinium (Gd) and HREE anomalies in the Powder River Basin can be explained by Cannonball Sea influence, and basin margin recharge, respectively. In the second, europium (Eu) and HREE anomalies in one of the deepest ( more than 7,600m) wells in Wyoming can be explained by hydro-geothermal leaching from the basement granite, and subsequent loss of LREEs during water migration to shallower reservoirs. In these case studies, the combined water and rock approach not only improves description of the system, but also independently predicts a local phenomena that had been previously proposed by Nealson et al., (2009). The combined water and rock approach allows better conclusions than in the original work of Nye et al. (2017). The approach recognizes that reactions with the reservoir rocks appear to be the primary factor in aqueous REE behavior. Contributors: Matt JOHNSON, Yuriy GANSHIN, Ghanashyam NEUPANE, and Tom MOORE. |