Applying Variscan Metasediments as an EGS Reservoir - A Conceptual 3D-Structural Model as a First Approach

To explore deformed Variscan meta-sediments as a potential geothermal reservoir for heat supply of the Göttingen University Campus, one of the first approaches is to set up conceptual 3D-structural model within the EU-Horizon-2020-MEET-project (Multidisciplinary and multi-context demonstration of Enhanced Geothermal Systems exploration and Exploitation Techniques and potentials). As a starting point for such a model, firstly the complex structures of the Variscan meta-sediments as seen in the Western Harz Mountains must be understood and characterized from micro to reservoir scale and a 3D real structural model created. To achieve this, various methods of data collection are undertaken from 3D digital data capturing and classic field methods to the digitization of literature data as well as sample collection from surface outcrops to boreholes. This study focuses on the characterization of the fracture network through topological analysis, defining two main parameters, connectivity and intensity and how these parameters change in various structural situations situated along the generalized fold and thrust structure, as a basis for understanding the complexity of the deformation exhibited in the Variscan Fold-and-Thrust belt. The results of this study do show a general trend of increased intensity and connectivity towards the fold hinge and thrust zone but are however more complex than this hypothesis, therefore concluding that a much more detailed study must be conducted before any such conclusions can be made.