3D seismic survey for geothermal exploration at Unterhaching, Munich, Germany

An increasing number of low-enthalpy geothermal power plants are being implemented in the Munich area with holes drilled into the Malm Formation (Upper Jurassic carbonates) to depths greater than 3000 m, where temperatures in excess of 100°C are encountered. Optimal development of geothermal productivity requires exploration of the geological structure, as well as information on the karstification of the Malm. Seismic surveys, including reprocessed older 2D lines from hydrocarbon exploration, new 2D lines filling gaps, and 3D surveys, are increasingly used for geothermal exploration. A geothermal power plant at Unterhaching, near Munich, has been producing heat and electrical power since 2009. A high resolution 3D seismic volume has been acquired over an area of 27 km2 for hydrological modelling purposes at the Gt2 reinjection well, located within the southern suburbs of Munich. First results show preferential hydraulic pathways along reactivated fault zones within the Malm reservoir which were partly active until the Aquitanian (Early Miocene). Additionally, a great number of sinkholes have been identified at the top Malm, located along fault zones which constitute new possible targets for geothermal exploration.