1Geological Institute, RWTH Aachen University, 52056 Aachen, Germany; 2Institute for Mine Surveying, Mining Subsidence Engineering and Geophysics in Mining, RWTH Aachen University, 52056 Aachen, Germany; 3Geological Survey of North Rhine-Westphalia, 47803 Krefeld, Germany
In the state of North Rhine-Westphalia (NRW), Devonian and Carboniferous limestones are widely available at depths with adequate temperatures for potential geothermal usage. However, they have not yet been sufficiently explored in order to realize local geothermal energy projects as a carbon-free heat source. This study presents the current status of the RWTH workgroup, introducing first insights on the geological interpretation of the EFRE-funded “KarboEx” project, which has the aim to assess the geothermal potential of carbonate rocks in the Ruhr area of NRW.
The preexisting knowledge and state of underground geological exploration and mine surveying from the coal mining in the German Ruhr Area in the past century are excellent preconditions for the assessment of the geothermal potential of the area. In no other geothermal exploration area in Germany such prerequisites exist to date (>1300 boreholes, of which >240 are over 1500 m deep; 1600 km of 2D reflection seismic lines; 200 km² of 3D seismic areas). For innovative geothermal exploration, the project will apply the most modern methods of data processing, seismic attribute analysis and geological interpretation of seismic data, which have been developed by the hydrocarbon industry during the past decades.
This study links previously published surface geological observations with newly reprocessed 2D seismic profiles and 3D surface seismic data from coal exploration, as well as stratigraphic, tectonic and well-log information from about 1300 deep exploration wells, old mining plans and other mine surveying records. Thus, a very high density of underground information is achieved, allowing a robust and detailed prediction of the subsurface geology in the target area. Additionally, abundant surface mapping data of Devonian Massenkalk and Carboniferous Kohlenkalk outcrops will assist the subsurface evaluation considering lateral stratigraphic, facies and diagenetic variations and changes.
Based on these data and using modern geological 3D modelling approaches, a basin-wide model of the carbonate aquifers occurring in the subsurface of the greater Ruhr Area will be constructed. The restoration of the pre-Variscan tectonic evolution of the study area using modern section balancing approaches will allow target-oriented subsurface structure and lithology prediction. This will further support large-scale models for potential fluid flow within the targeted carbonate horizons and will permit to constrain the geothermal exploitation potential of these rocks.
The innovation goal of the project is to develop an integrated exploration method for geothermal energy in order to support future exploration campaigns. Providing free accessible information on potential aquifers within the deep subsurface, the long-term goal is set to significantly facilitate and improve the development of deep geothermal projects to foster a carbon-free heat supply in NRW.
