Transient heat flow due to tectonic processes in the deep geothermal regime between the Nord Eifel-Venn Massif, Brabant Massif and adjacent Graben (Central Europe)

A 3D model for flow and heat transport is build, based on vitrinite reflectance measurements, fission track data, geophysical logging as well as core data from deep boreholes, geological maps and, balanced profiles. The model will be used to study the regional heat flow: key parameter for energy and cost efficiency of geothermal energy use of a deep borehole heat exchanger. The model is 40 by 40 square km with a depth of 5 km. It includes parts of Germany, Belgium and The Netherlands. The importance of the different tectonic processes for the thermal regime is demonstrated: extension, erosion & sedimentation, heat production, water flow (forced and free convection) and deep magmatic processes (Eifel Plume). These processes are investigated with respect to their thermal response time and there influence on present heat flow. Where appropriated, Greens response functions where used to study these processes. The tectonic events manifested in the studied area gives a heat flow diversity of 20 mW/m2. The hanging walls of the fault systems have an increased heat flow due to uplift, erosion and the large river valley, while the foot walls have a decreased heat flow due to down warp and sedimentation. These results in horizontal heat flow at the normal faults or the over thrust faults. The diversity is more pronounced for transient conduction. Long period temperature changes at to top or bottom of the model caused by deep plume or climatic changes at the surface yield a faster and deeper response in the hanging wall than in foot wall. These responses are caused by the higher thermal diffusivities of the older geologic rocks in the hanging wall.