Moving Source VSP for the Exploration of a Geothermal Reservoir

The Upper Jurassic (Malm) which is present in most parts of the Southern German Molasse Basin is a highly-productive aquifer with increasing depths and temperatures from north (Danube river) to south (Alps). For a geothermal power plant projected in Unterhaching, south of Munich/Germany, two boreholes (doublet) have developed the Malm at a depth of approx. 3000 m. The reprocessing results of available seismic profiles imply important decision criterions for possible karstification zones. Supplementary vertical seismic profiling (VSP)- and moving source (MS-) VSP-measurements were carried out in the Unterhaching Gt 1 well for a more detailed investigation of the vicinity of the production borehole. VSP and MS-VSP data deliver a higher seismic resolution than the reflection seismic profiles. The energy of one heavy vibrator was sufficient to image the Malm down to its basis (about 3500 m). A fault system and different influx areas within the Malm, measured during a hydraulic test, could be identified in the MS-VSP data.