Geologischer Dienst NRW, Deutschland
Hydrothermal energy is a future-oriented resource for climate-neutral heat production. The transnational EU-Interreg-funded “Roll-out of Deep Geothermal Energy in Northwest Europe (DGE-ROLLOUT)” project investigates one of the most promising reservoirs for deep geothermal energy exploitation in Northwest-Europe – the Rhenohercynian Basin.
Marine transgressive-regressive cycles enabled the formation of extensive reef complexes on the southerly continental shelf of the Laurussian palaeocontinent during mid-Palaeozoic times, whose remainders now form large parts of the Rhenohercynian Basin. Supported by favourable climatic conditions including warm, clear and shallow waters, the Givetian to Frasnian Massenkalk facies and the Dinantian Kohlenkalk Group, each several hundred meters thick, were deposited. Significant multiphase karstification of these Palaeozoic carbonate rocks, which can be observed in samples obtained from exploration boreholes and in nearby exposed counterparts, support their enhanced geothermal exploitation potential.
During the Variscan Orogeny, these Palaeozoic carbonate horizons were covered by voluminous paralic sedimentary rocks and deformed to large-scale, generally northeast-southwest-trending, syncline-anticline structures within the Rhenohercynian Zone. Alpine (post-)orogenic processes further induced faulting, resulting in fault-block tectonics in the Lower Rhine Embayment area of tectonic subsidence.
One major aim of the DGE-ROLLOUT project is the transnational characterization of the Dinantian carbonate reservoir in the subsurface of Northwest-Europe in order to facilitate the installation of geothermal power plants, and thus to support a CO2-neutral heat production. The hitherto unknown hydrothermal potential of the reservoir will be constrained by information on depth, thickness, structure and facies, which are currently being collected from the data pools of the geological surveys of Belgium, France, Germany and the Netherlands, together with new data from exploration wells and seismic surveys acquired within the scope of the project.
At the Geological Survey of North Rhine-Westphalia, 3D-modelling of the depths and dimensions of the subsurface lithologies and the nature of the subsurface geological structures is carried out using the commercial software MOVE [version 2019.1.0; Petroleum Experts Ltd]. The model is constrained by lithostratigraphic data obtained from drilling operations, geological mapping, and the interpretation of seismic profiles.
A compiled transnational potential map of the Rhenohercynian Basin in Northwest Europe will enable industrial and agricultural enterprises, as well as district heating providers to initiate deep geothermal heat projects with less prospecting risks.
