The community Pullach i. Isartal has been supplied with geothermal energy since 2005/2006, ERDWERK has played an important role providing well engineering and geological services.
Due to increasing demand, the operating company Innovative Energie for Pullach GmbH (IEP) decided in 2009 to expand the existing doublet with a third well. In the process, the original Pullach Th2 reinjection well was converted into a production well.
The research project "Pullach - Malm" (PUMA) utilised this opportunity in the South German Molasse, where a geothermal well was "turned around", ie. an injection well was converted into a production well. Hydraulic and chemical analysis, tracer tests and extensive modeling work provided insights into the changing characteristics of the well and gave direction to the long-term management of the Malm reservoir.
The research was conducted by the TU Munich Institute of Water Chemistry together with ERDWERK and the Aquasoil GmbH, Berlin. The project was funded by the PTJ / BMU and ERDWERK providing a 40% contribution to the research work.
The IEP GmbH, operator of the geothermal plant Pullach, supports the project technically and administratively.
The work aims to build in-depth understanding of the coupled hydraulic, thermal and hydrochemical processes in the operation of geothermal doublets in the Malm of the Bavarian Molasse Basin, in particular with regard to the predictive certainties for long-term operation and the potential expansion of existing facilities. In addition, the existing models and numerical models describing geothermal duplicates in Malmaquifer were reviewed and improved.
Main areas of work at ERDWERK
The focus of ERDWERK's role was the quantification of forecast uncertainty. On the basis of the project history this is presented in different scenarios. In the process, a prognosis was provided for the next expansion phase in order to subsequently evaluate using actual drilling results. The scenarios investigaed were as follows:
Scenario I: before the first drilling; Simulations with little statistical data from the molasse;
Target: Prediction for hole Th1, then evaluation based on real drilling results.
Scenario II: after the first drilling; Simulations as I, further comprising drilling the first hole, if necessary, further drillings in the Molasse Badin.Forecast for hole Th2, then rate real drill.
Scenario III: after the second drilling; Simulations like II, plus drill results from the second hole, forecast for hole Th3, then evaluation based on real drilling results.
Scenario IV: after evaluation of tracer tests, the hole Th2, simulations such as III, in addition to drill the second hole, forecast for hole Th3, then vote for real drill.
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