Geological controls on lithium production from basinal brines across North America

Abstract

With increasing lithium (Li) demands for electric car batteries and grid storage, additional Li beyond traditional continental brines and hard-rock sources might be necessary. Elevated Li concentrations have been reported in select oil field brines. Li could be extracted from the large volumes of saline fluids produced by oil and gas wells or from new wells dedicated to Li production. However, the spatial distribution of Li+ concentrations, the rates at which fluids can be produced in areas with elevated Li+ concentrations, and potential sources of Li enrichment are not well characterized. To help identify additional sources of Li, this study investigates the concentration, origin, and potential production rates of Li from sedimentary basin brines across North America. New Li data from brines in various stratigraphic units in the Paradox Basin are combined with existing datasets from the basin and others across North America. New Li analyses of organic-rich shales in the Paradox Basin are also examined to provide insights into the origins of Li. Results from this study show the median Li+ concentration in oil and gas produced waters across North America is ~5 mg/L; these generally low concentrations are unlikely to support Li production. However, higher Li+ concentrations (>65 mg/L) are found in select basins and strata containing deep saline fluids, associated with evaporation of paleo-seawater and precipitation of halite and potash salts, that have not been flushed by meteoric recharge. High Li content of organic-rich shales (range: 20–440 ppm; median: 60 ppm) interbedded with evaporites in the Paradox Basin suggest fluid-rock interactions with diagenetically-altered shales and organic matter are one potential source of Li-enrichment in basinal brines. Observed fluid production and injection rates indicate that Li production will likely be highest in sandstone and carbonate formations with relatively high permeability. Potential Li production rates can vary by orders of magnitude even within these strata due to heterogeneity in both Li concentrations and permeability, as well as recovery efficiencies between 40 and 70 % with current technology. Targeted Li production wells, rather than relying on existing oil and gas wells, would likely be necessary to produce brines at sufficient volumes to support Li production at these low concentrations. Co-recovery of other critical elements or combination with other subsurface developments, such as geothermal energy production, may make Li production from sedimentary basin fluids more viable.