Geothermal power plants require reservoirs of high temperature, high flow rates and sustainable recharge. Typically, there is a trade-off between increasing temperatures and decreasing fluid availability (due to pore space limitations) with depth. Predictions of the working conditions in reservoir formations at greater depth are challenging due to uncertainties in the underlying geology and because of the complex interaction of heat and fluid transport processes. We use new 3D geological models of Hesse (Germany) for a series of thermo-hydraulic simulations (BMWi-funded project “Hessen 3D 2.0”, FKZ: 0325944A+B). By quantifying the respective influences of conductive, advective and convective heat transport, we are able to subdivide the subsurface of Hesse into model domains of characteristic thermo-hydraulic regimes, and to obtain insights into reservoir temperatures and the hydraulic characteristics that control exploitable thermal energy resources. We further discuss these models in terms of their implications for the assessment of geothermal potentials represented by the application case of simplified hydrothermal doublets. The area of the northernmost part of the Upper Rhine Graben is identified as the most promising in terms of available geothermal energy. Convective heat transport within a sequence of thick and permeable graben filling sediments, favoured by low hydraulic gradients and a high heat input from the basement, result in a predicted geothermal potential between 1.7 and 2.5 MW per doublet. These results can assist to delineate where further exploration and future development for renewable heat supply should be encouraged.
Nora Koltzer (1), Judith Bott (1), Kristian Bär (2), Maximilian Frick (1), Mauro Cacace (1) & Magdalena Scheck-Wenderoth (1)
GFZ German Research Centre for Geosciences, Germany (1); TU Darmstadt (2)