Thermo-hydro-chemical modelling at the field- and lab-scales for a sustainable geothermal energy production in the Upper Rhine Graben – Geothermal project DEKAPALATIN-BERTHA

The Upper Rhine Graben in Germany is characterized by a heat anomaly and numerous normal faults crossing permeable sedimentary formations. These complex geothermal and hydrogeological conditions present both risks and opportunities for the geothermal exploration and development. Within the DEKAPALATIN-BERTHA project, located in the city of Wörth, Germany, we focus in the first phase on the understanding the controls on the thermal anomaly through dynamic numerical modelling. Besides, highly saline brines are well known to interact with the host rock in operating geothermal projects in the Upper Rhine Graben. However, this rock-fluid interaction during geothermal operation in not well elucidated quantitatively.  

Thermo-hydro-chemical (THC) coupling in geothermal reservoirs refers to the interrelated processes of heat transfer, fluid flow, and chemical reactions within the subsurface environment. This coupling has a significant impact on the hydrodynamic properties of the reservoir, as temperature changes can alter fluid viscosity and density. At the same time, chemical reactions can alter porosity and permeability through mineral dissolution and precipitation. Understanding and modelling THC interactions is critical for predicting reservoir behavior, optimizing energy recovery, and ensuring the long-term sustainability of geothermal operations. Incorporating THC processes into simulations improves the accuracy of predictions of fluid movement and heat distribution within geothermal systems.

Based on the 3D regional, structural GeORG model, we have built a 3D dynamic model capable of simulating coupled processes. Based on published data on the local hydrogeological stratification, we have resolved target formations such as the Muschelkalk and Middle Buntsandstein in detail. In addition, a gradual complication approach is adopted to investigate the key controlling factors on the heat anomaly. A series of THC numerical models at different scales have been developed prior to the laboratory experiments (µ-CT 3D scan and core flooding) for the optimal experimental setup. In this work we present our latest results.