Improving Economic Feasibility of Lithium Extraction from Produced Water

Abstract This study investigates an ion-exchange-based approach to enhance lithium concentration in produced brine, with application to geothermal, oilfield, and mining waterflooding operations. Coreflood experiments confirm that lithium actively participates in ion exchange, even in carbonate rocks with limited clay content. Lithium adsorption isotherms reveal that a significant amount of lithium potentially remain stored on exchange surfaces over extended waterflooding periods, unless specific desorption criteria are met. This implies that economically meaningful quantities of lithium could still be recovered from wells with long injection history. Numerical simulations at large scale show that lithium recovery primarily depends on two factors: the contrast in ionic strength between injected and formation brines, and the cation exchange capacity of the rock. Another simulation result highlights the roles of competing ions. For example, elevated salinity of formation brine can reduce lithium storage capacity. Based on systematic evaluation of numerical results with a wide range of input parameters, we provide general guidelines for enhancing lithium extraction. Economic projections suggest that incremented lithium yields may offset costs in well-flooding projects that would otherwise be considered economically unattractive. Finally, a short-term single-well injection-flowback scenario is explored. It tests the feasibility of early-stage field evaluation and lithium resource discovery. The model shows that an injection pill of 0.1 pore volume allows for detection of ion exchange through total mass balance, in the presence of a conservative tracer and moderate dispersion. Such tests are fast and inexpensive. They could guide the decision making process for lithium extraction and help identify zones with lithium-loaded exchangers for potential use in the future.