Seismic Exploration of Deep Hydrogeothermal Reservoirs in Germany

Abstract

Hydrogeothermal reservoirs that can be used for heating or electrical power generation are generally deeply seated in Germany, causing high drilling costs. Thus, it is essential for geothermal ventures to mitigate the exploration risk, which largely depends upon the flow rate encountered in a well. A geophysical method that images even small scale geological heterogeneities, is reflection seismic. Although proven for a long period in the hydrocarbon and mineral industry, its application to geothermal exploration poses new questions, which can only be answered if at least a regional reservoir model is established. The North German Basin, the Upper Rhine Graben and the German Molasse Basin constitute the most prospective areas in Germany.
By means of an example from the German Molasse Basin, the value of reflection seismic techniques like seismic facies analysis, seismic stratigraphy, structural inter¬pretation, seismic inversion, and attribute analysis is shown to derive information about a reservoir model. The benefits of 3D data is discussed: In the case of 2D seismic surveys the geologic features have to be inter- or extrapolated, the results being more ambiguous than mapping 3D seismic surveys. Facies distribution mapping may not be possible at all with 2D data. However, the costs of seismic exploration may contribute significantly to the total costs of a geothermal project.