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Assessment of Lithium-Rich Brine From the Smackover Formation by Analyzing Core, Geochemical, Petrophysical, and Productivity Data: Insights From Deep Evaporite-Carbonate Transitions.

Abstract

Smackover oil-field brines are considered a resource for lithium and exist as metal-rich brine anomalies in reservoir rocks across the Gulf Coast from east Texas to Florida. Very little, however, is known about the concentrating environment, grade-variability, and spatial distribution of lithium-rich water in the Jurassic Smackover Formation. Therefore, a preliminary study of published geochemical data, core, petrophysical logs, and production curves has been carried out to identify geologic and geochemical controls related to lithium-rich brines. The main objectives are to (1) calculate lithium reserves by analyzing production curves and volumetric methods, (2) map connected zones between the Norphlet, lower Smackover, and upper Smackover, and (3) identify the concentrating environment of the lithium-rich brines. Lithium-rich produced water from Norphlet and Smackover completions in east central Mississippi are deep basinal brines, and are defined from Sulin's classification as the “chloride-calcium” type. Further, as evidenced by the (Cl--Na+)/Mg2+ ratio, the lithium-rich brines are highly concentrated in chlorine with respect to sodium and magnesium. The Na+/Cl- ratio of Smackover brines is .35 and, according to Bojarski, brines of this nature accumulate with hydrocarbons. Scatter-plots of anions and cations were analyzed to determine the source of the brine relative to evaporating seawater, and indicate that the brines have been significantly altered versus the highest concentrations of lithium encountered in east central Mississippi. Therefore, the probable lithium brine concentrating environment is located in the sabkha to playa lake facies of the lower Norphlet Formation, as freshwater mixing, carbonate diagenesis, and clay dissociation all appear to be the controlling factors in altering the brine. Several petrophysical logs and production curves were gathered to analyze fluid volume, porosity, and production rates with known lithium-rich brine wells, and, core intervals reveal that the Norphlet-lower Smackover contact is gradational. The results of this assessment can be used to gain insight into (1) the potential source and concentrating environment of the lithium-rich brine trapped in the upper Smackover Formation, (2) brine geochemistry and diagenesis in sabkha environments, (3) the grade-variability and volume of lithium-rich brines in east central Mississippi, and (4) connectivity between the Norphlet and Smackover Formations.