Background

The municipality of Pullach i. Isartal, with its subsidiary Innovative Energie für Pullach GmbH (IEP), as one of the first municipalities in the region, has supplying public and private buildings with geothermally generated heat since 2005.

Since 2002, ERDWERK has been responsible for all geoscientific and drilling activities. In addition to issues relating to mining law, this includes the planning of deep boreholes, planning and evaluation of seismic investigations, site management during the execution of drilling work and operational support, e.g. in matters relating to permits.

Geothermal Doublet

The first two deep holes, Pullach Th1a and Pullach Th2, were drilled in 2004 / 2005 at depths of 3,930 m and 4,120 m (MD) respectively. Both wells (one injection well and one production well) exploit the Malm carbonates that serve as thermal water reservoirs in the Bavarian Molasse Basin.

Extension to Triplett

Only a few years after the doublet was commissioned, the expansion of the plant was foreseeable in view of the high growth rates in the heating network. To this end, 2D-seismic surveys were carried out in 2009 to find an optimal drilling location and suitable development targets for a third well.

In early 2011, the Pullach Th3 well was drilled from its own well site. Compared to the two older doublet wells, which exploited the reservoir with a final drilling diameter of 6.1/8" and 5.7/8" respectively, a larger drilling diameter of 8.3/8" was selected for the Pullach Th3 well. Thanks to the very fast drilling time of only 56 days, the third well was successfully completed to a final depth of 3,984 m. The third well was drilled to a diameter of 8.3/8". Due to the hydraulic properties of the wells, the third well has been used as a reinjection well and the Th1a and Th2 wells as production wells since the triplet was commissioned. For the first time, a well used as an injection well was rededicated as a production well (Pullach Th2).

With the expansion of the geothermal plant, which was completed in 2011, its capacity was approximately doubled. In the meantime, 48 percent of Pullach's heat demand can be covered by geothermal heat.

Outlook

As the demand for regenerative heat in Pullach i. Isartal continues to rise, the IEP has been working on  further expansion of the geothermal project since 2017. As a first step, at the beginning of 2018, together with the geothermal neighbours and partners, SWM GmbH and Erdwärme Grünwald GmbH, an area of approx. 100 km² was surveyed using 3D-seismic techniques to investigate possibilities of further thermal water sources. The seismic campaign was carried out in a time and cost efficient way thanks to a wireless measuring method which was new in Germany. First results show an excellent quality of the obtained data. Planning is currently underway for the expansion of geothermal energy in the Pullach area.