Multi-Disciplinary Prospection Approach for EGS Reservoirs in the German Variscian Basement

Abstract

The central and south German Variscian crystalline basement is considered to be the largest geothermal resource of Germany. The southern Black Forest is a representative example of this basement and has thus been selected for the investigation of exploration tools.

It is an issue, in particular for the geophysical exploration to image fractured zones and potential reservoirs in a basement environment at greater depth since seismic methods require complex and costly processing. Often they are anyhow limited to the topmost part of the basement. In the presented GKW project geological, geophysical and numerical methods have been combined in order to assess geothermally interesting structures in the Southern Black Forest.

A 3D geological model has been the base for spatial temperature prediction. Sophisticated structural methods such photogrammetric have completed the surface studies and used for assessing the different type on fault zones. Magnetotelluric studies were applied to investigate the deep structures and their distribution of electric conductivity, which has been shown to be a good indicator of thermal anomalies. The investigation of Bouguer anomalies may provide a link between the surface structures and the electric conductivity anomalies at depth.

Re-coupling between the different anomalies and the temperature model allows for identification of the optimal geothermal site in the investigated area from the point of view of the underground. In the same project a heat sink analysis has revealed also potential users with different temperature levels.