At the end of 2005, SWM Services GmbH took over the exploration rights for geothermal energy for the "Sauerlach" field in the south-east of Munich. This was the starting signal for the development, planning and implementation of one of the largest geothermal projects from deep hydrothermal geothermal energy in Europe at that time. After several years of positive experience with their first geothermal plant in Munich-Riem, SWM wanted to expand its portfolio with a further geothermal plant in Sauerlach.
ERDWERK was commissioned by SWM with the geological-technical planning and technical management in the implementation phase.
For the development planning and technical planning of the wells, knowledge and data from the Hofolding 1-4 and Endlhausen 1 KW exploration wells near the site were used, among other sources. Furthermore, 51 km of seismic data was reprocessed to optimize development planning and further minimize risk.
On this basis, a development concept with 2 doublets was finally defined, which was later implemented.
Well Site Construction and Start of Drilling
The preparation of the drilling site on the eastern outskirts of Sauerlach began in July 2007 on an area of approx. 13,000 m². In the center of this area the drill cellars with the approx. 50 m deep standpipes were erected. The drilling site was designed in such a way that in the following drilling phase it offers sufficient space for the drilling rig including the technical equipment, work containers, pipe storage and test equipment. Drilling finally began at the beginning of October 2007.
Drilling and Testing Work
With ITAG Tiefbohr GmbH, Stadtwerke München was supported by an experienced drilling company as general contractor, which had already successfully drilled geothermal boreholes in the molasse at the time. The performance of the ITAG Rig 23 drilling rig used, with a control hook load of 365 t and a mast height of 45 m, was stretched to its limits by the demanding drilling operations.
Finally, a total of three deep geothermal wells were drilled in Sauerlach. Based on the findings and test results, a fourth well was not drilled. All three boreholes reached the target horizon of Malm, partly with very long deflection distances (up to max. 2.4 km) and very high technical demands, with Th1a and Th2 connecting it with a final diameter of 8.1/2" and Th3b with a final diameter of 6.1/8".
In the Th1, borehole instabilities led to a necessary side track out of the parent well. The Th1a well reached a final depth of 4,757 m MD (4,179 m TVD) with a successful deviation to the west. The Sauerlach Th2 well reached a final depth of 5,060 m MD (4,181 m TVD) after a total deviation of more than 2 km to the north. The third well Th3b (direction SE) successfully reached the target horizon of Malm in May 2009 with a depth of 5,567 m MD (4,480 m TVD) and was thus (at the time) the deepest geothermal well in Europe.
The wells were hydraulically tested and stimulated with acid after reaching their final depths as part of the in-production setting work. Based on the results, the operational triplet concept with one production well and two reinjection wells was defined, which was unique for the extraction of deep geothermal heat in the South German molasse basin.
After dismantling and partial recultivation of the drilling site (2011) and completion of the power plant, the geothermal power plant was commissioned, and trial operation was carried out at the end of 2013.
Since then, the geothermal power plant with the geothermal triblette has been in operation, whereby waters heated to over 140 °C are extracted from the Th1a and reinjected into the two boreholes Th2 and Th3b (production rate approx. 110 l/s). In addition to electricity production, demand-oriented heat from the return flow of the power plant is provided for the local heat supply in Sauerlach (local heat).
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