New Approaches for Enhanced Geothermal Systems Research in Europe
New technology has the potential to significantly increase the use of the available geothermal resources. While conventional geothermal resources cover a wide range of uses for power production and direct uses in profitable conditions, a scientific and industrial community has been involved in promoting Enhanced Geothermal Systems, the so-called EGS concept. The enhancement challenge is based on several non-conventional methods for exploring, developing and exploiting geothermal resources that are not economically viable using conventional methods.
Lower Permian siliciclastic sediments and volcanics are widespread strata throughout Central Europe forming deeply buried aquifers in the North German Basin with formation temperatures of up to 150°C. The average depth of these structures is 4000 m. They are investigated to develop stimulation methods to increase the permeability by enhancing or creating secondary porosity and flow paths. For these purposes, an in-situ downhole laboratory was established in Gross Schoenebeck, north of Berlin, Germany. At present, two 4.3 km deep boreholes have been drilled into Lower Permian strata. The first well originally completed in 1990 as a gas exploration well and abandoned due to non-productivity, was re-opened in 2000. Afterwards, the well was hydraulically stimulated in several treatments between 2002 and 2005. In 2006, the second well planned for extraction of thermal waters was drilled in order to realize the doublet system. Most recently, both the Lower Permian sandstones and the volcanic rock in the new well were stimulated. The resulting engineered reservoir has an increased productivity requiring minimized auxiliary energy to drive the thermal water loop and has a minimized risk of a temperature short circuit of the system during a planned 30-year utilization period. The forthcoming phase is designed to demonstrate sustainable hot water production from the reservoir between the two wells with a long-term circulation experiment.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009