A Multi-proxy Approach for Fracture Network Quantification of Regional Fold and Thrust Structures for Geothermal Reservoir Characterisation

Within the Horizon 2020 MEET project (Multidisciplinary and multi-context demonstration of Enhanced Geothermal Systems exploration and Exploitation Techniques and potentials) is to bring about this potential in previously considered unconventional geothermal reservoirs, focusing specifically on crystalline and meta-sedimentary Variscan
basement rocks. One of the demo sites is located at the University of Göttingen with the reservoir at 4km depth, within the Variscan sedimentary basement.
With no research well and little in the way of seismic interpretation, the focus has been put onto the use of outcrop analogues within the Rhenohercynian zone to determine the potential of such a reservoir. The focus of this study is primarily within the Clausthal Culm Fold Zone (CCFZ) in the Western Harz Mountains, comprised of NW verging folds
of Lower Carboniferous greywackes and slates. With the complexity of the structural and lithological attributes of the reservoir, along with limited subsurface data, a methodology has been established to characterise the main target areas within the CCFZ for the collection of fracture network parameters for use in fluid flow and DFN models. By
collecting field data in various forms such as drone images and 3D outcrop models, the structural and lithological situations can be characterised, and an overview of the changes of the fracture network characteristics can be quantified. This method focuses on the fracture characteristics based on their relationship to the lithology and placement within a fold rather than physical location, allowing for a more holistic approach for a potential development reservoir permeability in cases where subsurface data is limited.