Search

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.

To limit global warming to 2 °C above pre-industrial levels, our society is confronted with the urgent need to make the transition to a globally sustainable energy system (1). Geothermal energy is available regardless of season or time and, unlike many other renewable energies, is therefore suitable for base-load sytems. Geothermal energy is regarded as renewable as heat flows back into the reservoir due to temperature conditions and transport processes. It uses the energy source from the earth’s interior, which is inexhaustible by human standards. Geothermal energy can play an important role in the decarbonization of the energy system in Germany. In Central Europe, the greatest geothermal potential lies in the crystalline basement with important hotspots in areas under tectonic tension. These include the Upper Rhine Graben as a rift zone with hydrothermal fluid flows and exceptional temperature anomalies in the deep underground (2). The technology “Enhanced Geothermal Systems” (EGS) was developed to exploit the geothermal potential in the crystalline (3). EGS use the deep fractured subsoil as a natural heat exchanger. With at least two boreholes, a thermal water cycle is created that brings geothermal energy to the surface and makes it usable (4). However, since relatively high flow rates (> 10 l/s) are required for economic operation, the natural permeability of the rock in the crystalline – in contrast to hydrothermal systems – must be increased by hydraulic or chemical stimulation measures (reservoir engineering) to increase the flow rates. A major challenge for EGS is to control and minimize the induced seismicity generated in this process, both in the reservoir engineering and operation phase and with a view to increasing public acceptance. A profound understanding of the multi-physical processes in the reservoir, such as the complex interactions of the fluid with the reservoir at high flow rates, is indispensable for this. New scientifically based strategies and technologies are urgently needed to exploit the geothermal potential economically and at the same time in an environmentally compatible way.