Title: GeoLaB - Geothermal Laboratory in the Crystalline Basement

Thomas Kohl1, Eva Schill1, Judith Bremer1, Günter Zimmermann2, Olaf Kolditz3, Ingo Sass4

1KIT, Germany; 2GFZ, Germany; 3UFZ, Germany; 4TU Darmstadt, Germany

Event: GeoKarlsruhe 2021

Date: 2021

DOI: 10.48380/dggv-2p9j-dr38

In Central Europe, the largest geothermal potential resides in the crystalline basement rock with important hotspots in tectonically stressed areas. To better harvest this energy form under sustainable, predictable and efficient conditions, new focused, scientific driven strategies are needed. Similar to other geo-technologies, the complex processes in the subsurface need to be investigated in large-scale facilities to ensure environmental sustainability.

The proposed new underground research laboratory GeoLaB (Geothermal Laboratory in the Crystalline Basement) will address the fundamental challenges of reservoir technology and borehole safety. The specific objectives of GeoLaB are 1) to perform controlled high flow rate experiments, CHFE, in fractured rock, 2) to integrate multi-disciplinary research to solve key questions related to flow regime under high flow rates, or higher efficiency in reservoir engineering, 3) risk mitigation by developing and calibrating smart stimulation technologies without creating seismic hazard, and 4) to develop save and efficient borehole installations using innovative monitoring concepts. Planned experiments will significantly contribute to our understanding of processes associated with increased flow rates in crystalline rock. The application and development of cutting-edge tools for monitoring and analyzing will yield fundamental findings, which are of major importance for safe and ecologically-sustainable usage of geothermal energy and further subsurface resources. As an interdisciplinary and international research platform, GeoLaB will cooperate with the German Research Foundation (DFG), universities, industrial partners, and professional organizations to foster synergies and technological and scientific innovations.

GeoLaB is designed as a generic underground research laboratory in the crystalline rock adjacent to the Rhine Graben, one of the most prominent geothermal hotspots in Germany. GeoLaB is an analogue site representative of the world‘s most widespread geothermal reservoir rock, the crystalline basement. In an initial phase, the suitability of a site for GeoLaB located either in the Black Forest or the Odenwald, will be proven by geological, geophysical, and geochemical drilling exploration. At the selected site, a two km long gallery will be excavated, tapping individual caverns, from which controlled, high flow rate experiments will be conducted. The experiments will be continuously monitored from multiple wells, drilled from the underground laboratory or from the surface. This will create a unique 4D-benchmark dataset of thermal, hydraulic, chemical and mechanical parameters. A virtual reality concept accompanies the development of the complex infrastructure concept from the very beginning, supporting the infrastructure set-up and the scientific experiments in planning, documentation and analysis.

GeoLaB will become a cornerstone for the target-oriented development of the enormous geothermal resource. With its worldwide unique geothermal laboratory setting, GeoLaB allows for cutting-edge research, associating fundamental to applied research for reservoir technology and borehole safety, bridging laboratory to field scale experiments and connecting renewable energy research to social perception. GeoLaB comprises a novel approach that will shape research in earth science for the next generations of students and scientists.

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