THE ORIGIN AND ENRICHMENT OF LITHIUM-RICH OIL FIELD BRINES: A CASE STUDY FROM THE DEVONIAN LEDUC FORMATION, ALBERTA BASIN, CANADA

The direct extraction of critical minerals from low temperature brines and oil field produced water is emerging as a potentially economical and environmentally improved extraction methodology. Resource characterization and field-tested lithium production via direct lithium extraction technologies of Smackover Fm. (Arkansas, USA) and Leduc Fm. (Alberta, Canada) brines indicate a promising domestic supply of lithium from oil field brines. Elevated lithium concentrations (>50 mg/L) are known in oil fields across North America (e.g., Paradox, Appalachian, Williston Basins) but the origin of these brines, source of the lithium, and mechanisms for lithium enrichment are largely debated or unknown. Using the Devonian Leduc Fm. resource, we document the complexity of unraveling brine generation and evolution and lithium source and enrichment in oil field brine resources. The presence of high lithium concentrations (50-140 mg/L) have been documented in the Alberta Basin since the 1960s. The lithium resource within the Leduc reservoir brines have been estimated at 16.0 Mt lithium carbonate equivalent with an average lithium concentration of 75 mg/L. Competing hypotheses exist regarding Leduc Fm. brine origin (evapoconcentration of seawater, dissolution of evaporites, magmatic/hydrothermal fluids) and post-formational brine modification (migration – connate vs. exotic brine, dilution with meteoric water, mineralization – e.g., dolomitization, dewatering of clay minerals/gypsum). Additionally, lithium source (clay minerals in reservoir, subaerial/subsurface rock-water interactions, exotic lithium-rich fluids) and lithium brine enrichment mechanisms confound understanding of resource homogeneity and longevity. In this presentation we summarize the Leduc brine geochemical characterization and potential lithium sources. We also discuss a path forward for interrogating the origin of oil field brine resources using multiple isotopic systems (𝛿⁷Li, ⁸⁷Sr/⁸⁶Sr, ∆’¹⁷O) applied to both the brine and reservoir host rock.