IDENTIFYING LITHIUM ENRICHMENT MECHANISMS UTILIZING PRODUCED WATER ISOTOPIC COMPOSITIONS FROM THE UTICA/POINT PLEASANT FORMATION

To meet predicted 2050 energy storage demands, global lithium (Li) production requires an approximate 500% increase. Oil and gas produced water, wastewater brought to the surface during hydrocarbon production, comprises brines that can contain total dissolved solids (TDS) concentrations upwards of 10x greater than seawater (35,000 mg/L) and can contain Li concentrations >100 mg/L. While utilizing produced water Li concentrations alone can be useful to identify locations for potential Li extraction from deep basinal brines, there is also value in expanding our understanding of the sources and mechanisms responsible for Li-enrichment or lack thereof. In this study, we measured the isotopic compositions (δ⁷Li, δ¹¹B, δ¹³⁸Ba) from both produced water and core samples of the Ordovician Utica/Point Pleasant (Utica) Formation, Appalachian Basin, USA. Our results suggest that there are depth-dependent thermal maturity and water-rock controls, such as clay mineral diagenesis, on Li concentrations in the Utica Formation. For instance, produced water Li concentrations from the Utica Formation are most enriched where the Mg/Li molar ratios and the δ⁷Li are relatively low while depth and temperature are relatively high. Appalachian Basin brines from geologic formations between the Marcellus and the Utica Formation demonstrate the potential for future Li resource recovery (>80 mg/L). Our results provide mechanistic insight for predicting Li enrichment in the Utica Formation which may help inform future efforts at Li resource recovery from these deep formation brines.