Facies-Related Evaluation of the Geothermal Reservoir Potential of Devonian Carbonates in North Rhine-Westphalia, Germany

Summary Deep geothermal reservoirs can provide sustainable energy for district heating systems of metropolitan areas. In the Munich area (Bavaria, Germany) geothermal heat is supposed to be the major energy provider for the city's district heating network by 2040, since carbonate reservoir formations of Upper Jurassic age offer ideal geological conditions. In the Rhine-Ruhr area of western Germany, where Europe's largest district heating network is located, deep carbonate formations of Middle to Upper Devonian age are available in about 4 km depth. Thus they depict potential geothermal reservoirs for the local district heating system, as well. As the reservoir potential of this formation is widely unexplored, the present study aims at evaluating the general reservoir suitability of the Devonian carbonates and at identifying the facies types exhibiting the most favorable structural geological and petrophysical features. The main tool were outcrop analogue studies conducted in the carbonate belts south of the Rhine-Ruhr region. By comparing the findings of the present study with the ones of outcrop analogue studies driven out in the Munich area, the general suitability of the Devonian carbonates could be confirmed. Furthermore the reef-dolomite facies emerged as the most promising sub-formation.