A Model for sCO2 Storage in Superhot Geothermal Systems

Superhot geothermal systems, characterized by pressures exceeding 22 MPa and temperatures above 374°C and therefore water being found in its supercritical state, offer a unique opportunity to integrate renewable energy production with carbon capture and storage (CCS). In these systems, supercritical CO₂ (sCO₂) has a higher density than water, enabling the formation of a sinking CO₂ plume that minimizes leakage risks while simultaneously utilizing in-situ geothermal fluids for energy supply. In this presentation, we demonstrate our recent study on the dynamics of CO₂ injection and migration in both unfractured, homogeneous, and fractured geothermal reservoirs. Our simulation workflow includes a stochastic fracture network generator that can incorporate various parameters, such as fracture dimensions, strike and dip angles, and fracture network restrictions. Furthermore, the exchange of heat and mass between fracture networks and the surrounding matrix was realized using transfer coefficients rather than a combined grid. This poses numerical challenges that will be discussed during the presentation.

In addition, results from selected simulation runs will be presented, based on different reservoir permeabilities and specific fracture network characteristics, regarding CO₂ plume behavior, breakthrough dynamics, and temperature distributions within the reservoir. Overall, high permeability is favorable, while fractured reservoirs exhibit complex migration patterns. Temperature analysis confirmed minimal cooling effects, ensuring long-term operation. In conclusion, our study highlights the conditions necessary for combining CCS and superhot geothermal energy utilization and provides a 3D model for future evaluations.