Fracture Geometry and Permeability Evolution in Response to Thermo-poro-chemo-mechanical Processes During Circulation in EGS

ABSTRACT: The Chemical dissolution and precipitation processes in geothermal reservoirs can play a crucial role in optimizing the efficiency, cost-effectiveness, and sustainability of energy production. Mineral dissolution and precipitation occur when the injected fluid is undersaturated or supersaturated, respectively, impacting fracture permeability and the overall system performance. This study investigates the effects of silica and calcite dissolution and precipitation on fracture aperture under geothermal conditions using a single component approach. When undersaturated cold water is injected, silica dissolution enhances permeability by increasing fracture aperture, improving fluid flow and heat extraction. Conversely, silica precipitation in high-temperature regions reduces fracture aperture, restricting permeability. Calcite exhibits similar behavior but with distinct solubility characteristics. Its dissolution is initially prominent near the injection well but declines over time due to reduced reaction rates. In supersaturated conditions, calcite precipitation occurs rapidly where the solute front arrives before the temperature front, leading to permeability reduction. The study highlights the complex dependence of solubility on temperature, with silica exhibiting increased dissolution and precipitation rates at higher temperatures, whereas calcite dissolution is favored due to increased equilibrium concentrations with temperature.