Solutions for Thermally-driven Reactive Transport and Porosity Evolution in Geothermal Systems (“Reactive Lauwerier Problem”)

Abstract. Subsurface non-isothermal fluid injection is a ubiquitous scenario in energy and water resources applications, which can lead to geochemical disequilibrium and thermally-driven solubility changes and reactions. Depending on the nature of the solubility of a mineral, the thermal change can lead to either mineral dissolution or precipitation (due to undersaturation or supersaturation conditions). Here, by considering this thermo-hydro-chemical scenario and by calculating the temperature-dependent solubility using a non-isothermal solution (the so-called Lauwerier solution), thermally-driven reactive transport solutions are derived for a confined aquifer. The coupled solutions, hereafter termed the “Reactive Lauwerier Problem”, are developed for axisymmetric and Cartesian symmetries, and additionally provide the porosity evolution in the aquifer. The solutions are then used to study two common cases: (I) hot CO₂-rich water injection into carbonate aquifer; and (II) hot silica-rich water injection, leading to mineral dissolution and precipitation, respectively. We discuss the timescales of such fluid-rock interactions and the changes in hydraulic system properties. The solutions and findings here contribute to the understanding and management of subsurface energy and water resources, like aquifer thermal energy storage (ATES), aquifer storage and recovery (ASR) and reinjection of used geothermal water. The solutions are also useful for developing and benchmarking complex coupled numerical codes.