| Abstract |
Within the scope of the research project "3D-Model of the deep geothermal potentials of Hesse" the deep geothermal potential of the Federal State of Hesse was assessed. The quantification of the heat stored under ground and the analysis of the deep geothermal potential was done for different geothermal systems, as hydrothermal and petrothermal systems (enhanced geothermal systems) as well as fault zones and closed systems as deep borehole heat exchangers. Knowledge of the geological structure and the geothermal properties of the potential reservoir rocks as well as the reservoir temperatures are indispensable for this approach. Therefore, the geological structure and the temperature distribution in the subsurface was modelled in 3D to a depth of 6 km below ground. To allow predictions of the geothermal properties, a data set of outcrop analogue studies, borehole data and core investigations as well as hydraulic test data was compiled for all relevant formations. Systematic measurements of thermophysical and hydraulic rock properties such as thermal conductivity, thermal diffusivity, heat capacity, density, porosity and permeability of relevant geologic formations was combined with in situ temperature measurements, hydrothermal upwelling zones, characteristics of geological faults and were added to the 3D geological structural model. Since both the hydraulic and thermophysical properties depend on the in situ conditions of the reservoir, the lab and field data need to be adapted accordingly. Therefore, the outcrop analogue data was correlated with in situ data from hydrocarbon exploration wells to develop empiric functions for their depth and temperature dependency. Using the example of the petrothermal potentials we present a newly developed multiple criteria approach, which assesses various rock and reservoir properties and their relevance for the different geothermal system to define the overall potential of each system. The method can be used for a 3D-grid based identification and visualization of different geopotentials using various parameters to determine each potential. Therefore, threshold values for each parameter had to be defined to specify the grade of potential. The resulting geothermal model, which incorporates the quantification and the analysis of the deep geothermal potentials, defines the location of high potential areas where further exploration and future exploitation of the geothermal resources is feasible and shows that overall the geothermal potential is high enough to cover the energy demand of the whole federal state of Hesse. Additionally, it is available online as an instrument for public information and can be used as an important tool for the exploration and planning phase for the design of geothermal power plants. |