| Abstract |
As the technology and demand for renewable energy increases across the globe, lithologies and tectonic settings not classically thought of having a technical geothermal potential, are receiving more and more attention to be exploited by Enhanced Geothermal Systems (EGS). One of the aims of the EU-Horizon-2020-MEET-project (Multidisciplinary and multi-context demonstration of Enhanced Geothermal Systems exploration and Exploitation Techniques and potentials) is to explore and bring about this potential in Variscan crystalline and meta-sedimentary reservoirs. The Göttingen University Campus, Germany, was selected as one of the demo sites for the MEET-project, due to the University’s interest to convert the natural gas power and heat plant, into a deep geothermal power plant to supply the existing district heating. Until the targeted 2000 m research borehole is drilled and since in the Göttingen area the expected deformed meta-sediments are covered by a Permo-triassic sedimentary cover of 1500 m, the analogue site for this project has been chosen as the Western Harz Mountains, where the Variscan fold and thrust belt experienced an uplift to the surface mainly during the Cretaceous. From interpolation of comparable units in the Rhenish Massif with the Harz Mountains, it is likely that the boundary that separates the Variscan autochthonous from the allochthonous zone is striking through the subsurface of the area of Göttingen, just 40 km south west from the Harz. This paired with the reasonable outcrop situation makes the Western Harz a suitable analogue for the Variscan meta-sedimentary basement of Göttingen University Campus. To understand and comprise the complex structural parameters that may be found in the expected slate and greywacke units beneath the surface of Göttingen, a 3D conceptual structural model of the Variscan basement must be created as the first step. This contribution will focus on the interactions and changes of different structural parameters across the typical Variscan fold and thrust belt at reservoir, outcrop and microstructure scale. To accomplish this, intensive field campaigns and photogrammetry sessions are undertaken for detailed data collection on changes in parameters such as the fracture network, mineralisation and lithology across the primary fold and thrust structure. The data collection is comprised of samples taken from outcrops at the surface and subsurface, as well as drill cores. Based on the presented conceptual model created from real structural situations and the following petrophysical and chemical parameterisation derived from lab experiments, reservoir models and EGS-exploitation strategies can be developed. |