Multiple target horizon exploration for the implementation of an integrated geothermal system for Göttingen, Germany

To boost the contribution of geothermal energy to Europe’s energy transition, exploration and exploitation must extend to new regions and play types. The MEET (Multidisciplinary and multi-context demonstration of EGS exploration and Exploitation Techniques and potentials) project included analysis of the potential for an Enhanced Geothermal System (EGS) in the metasedimentary rocks of the Variscan Fold and Thrust Belt in the subsurface at the University of Göttingen, Germany. A feasibility study related to the integration of EGS into the existing district heating system of the Göttingen University campus, which currently uses a natural gas-based combined heat and power plant, presents several scenarios with minimum requirements for cost-effectiveness of the EGS, e.g. a brine flow rate of 30 l/s and brine temperature of 130°C. Mohr diagrams are used to predict the responses of the rocks to thermal and hydraulic stimulation, using information from geological analogue studies in the nearby Harz Mountains, and petrophysical data measured in the laboratory.We focus on targeting multiple geological horizons to reduce the exploration risk and to optimize the geothermal energy system, including the development of deep, medium deep and shallow geothermal systems for heating, cooling, and heat storage. A concept based on these geothermal systems together with other renewable energies and energy-efficiency measures is proposed. The geology at Göttingen is suitable for such an integrated geothermal system. It includes Variscan basement rocks below ~1500 m, Zechstein layers with salt, gypsum and carbonate layers (up to 500 m thick), and Mesozoic sandstones and possibly karstified carbonates. Unconsolidated Pleistocene sediments are suitable for shallow geothermal systems. The multiple target horizons approach can be more appealing for funding because of the possibilities of higher output and greater efficiency. It will also decrease the exploration risk because fall-back options are available. Involvement and engagement of different stakeholders is a potential barrier to such an integrated approach.MEET received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement № 792037