FROM OIL BRINES TO SUSTAINABLE ENERGY: UNRAVELING LITHIUM ACCUMULATION IN DEVONIAN BRINES OF ALBERTA

Current battery technologies heavily rely on lithium (Li), sourced traditionally from evaporation ponds, pegmatites, and clay deposits. However, the exploration of alternative, environmentally friendly sources with lower Li concentrations, such as oil brines, has gained momentum. With the cooperation of industry operators, the Alberta Geological Survey (AGS) conducted an extensive brine sampling program, collecting 312 samples from 309 wells. This presentation illustrates the investigation of 183 Devonian brine samples collected from the Granite Wash, Keg River, Swan Hills, Slave Point, Leduc, Nisku, and Watt Mountain formations, in addition to parts of the Wabamun Group. The geochemical analysis encompassed major ions, dissolved metals, halogens (Cl and Br), alkali metals (Rb, Cs, Li, K, Na), and isotopes (δ18O, δ2H, δ7Li, δ11B, and 87Sr/86Sr).

The Devonian brines of Alberta were classified into two primary groups: Lower-Middle Devonian and Upper Devonian, based on their δ2H and δ18O compositions and Rb/Cs molar ratios. The δ7Li and δ11B isotope values indicated that Li was adsorbed from seawater and accumulated within fine-grain marine sediments. The 87Sr/86Sr values revealed the migration paths taken by Li-enriched fluids, which likely resulted from tectonic compression during the Laramide orogeny, causing the expulsion of fluids from hydrated minerals, clays, and other fine-grain lithologies. Subsequently, these fluids were mixed with residual evaporite brines already present in Upper Devonian carbonate reservoirs. Over time, these brines underwent additional chemical alterations due to diagenetic processes, water-rock interactions, and varying degrees of mixing with meteoric waters.

To further investigate the origin of Li, geochemistry data is being collected from lithologies resembling potential source rocks by using alkali metals, δ7Li, δ11B, and 87Sr/86Sr isotope ratios. The primary goal of this research is to attain a comprehensive understanding of the mechanisms responsible for lithium and other metal enrichment in the Alberta basin.