A simulation study of the impact of fracture networks on the co-production of geothermal energy and lithium

TL;DR

This study uses high-resolution numerical simulations to analyze how fracture network structures in geothermal reservoirs influence lithium and energy co-production, highlighting the critical role of fracture geometry in lithium extraction efficiency.

Contribution

It introduces a detailed simulation approach to assess the impact of fracture heterogeneities on lithium and energy production in geothermal systems, emphasizing fracture characterization.

Findings

Fracture network geometry significantly affects lithium production.

Lithium production is more sensitive to fracture structure than energy output.

Heat conduction and lack of mineral recharge limit lithium recovery.

Abstract

Co-production of geothermal energy and lithium is an emerging opportunity with the potential to enhance the economic potential of geothermal operations. The economic reward of extracting lithium from geothermal brine is determined by how the lithium concentration evolves during brine production. In the initial stage, production will target lithium contained in the brine resident close to the production well. While lithium recharge, in the form of rock dissolution and inflow from other parts of the reservoir, is possible, the efficiency of such recharge depends on the geology of the reservoir. In this work, we study how structural heterogeneities in the form of fractures impact the flow of lithium-carrying brine. Using a numerical simulation tool that gives high resolution of flow and transport in fractures and the host rock, we study how the presence of fractures influences energy and lithium production. Our simulations show that, due to heat conduction and the lack of mineral recharge from the rock, differences in fracture network geometries have a much larger impact on lithium production than energy production. The simulations thus confirm that in addition to the geochemical characterisation of lithium in geothermal brines, understanding fracture characterisation and its impact on production is highly important for lithium production.