Geochemical and lithium isotope tracking of dissolved solid sources in Permian Basin carbonate reservoir and overlying aquifer waters at an enhanced oil recovery site, northwest Texas, USA

Groundwater from the Triassic Dockum Group-Santa Rosa aquifer (δ7Li range of +20.6 to +23.5‰) is isotopically distinct from waters from the overlying Ogallala Formation (+10.6 to +16.5‰) and the deeper San Andres Formation, indicative of hydrologic isolation from both meteoric recharge and from deeper brines in the field area. In addition to tracking groundwater-brine mixing and water-rock interaction, temporal changes in the δ7Li composition of deep groundwater in the study area has potential use in the early detection of upward or injection-induced brine migration, prior to its incursion into the sensitive overlying Ogallala aquifer.