Deutsche Erdwärme starts long-term test in Graben-Neudorf
Rig operations at Graben-Neudorf geothermal project site, Germany (source: Deutsche Erdwarme)
Alexander Richter
12 Nov 2025
Deutsche Erdwärme has launched a long-term productivity test at its 3,600-metre geothermal well in Graben-Neudorf, Germany’s hottest deep reservoir.
After months of pause, activity has resumed at Deutsche Erdwärme’s geothermal project in Graben-Neudorf, southwest Germany. The company has begun a long-term production test to confirm the productivity of its 3,600-metre-deep well, a key step toward establishing one of the country’s most advanced geothermal plants.
The test, expected to run for two to three weeks, involves injecting water into the subsurface to monitor pressure behaviour and microseismic response. Results will determine whether the well can deliver sufficient thermal output for future power and heat generation.
Unique test in Germany’s Upper Rhine region
According to Deutsche Erdwärme CEO Herbert Pohl, such a long-term test has never been carried out in Germany or the Upper Rhine Graben. The site in Graben-Neudorf has been under geological study for more than 30 years. The current phase focuses on verifying sustainable reservoir management and simulating operating conditions for future continuous production.
Throughout the testing period, several injection cycles will be conducted under controlled pressure levels to avoid induced seismicity — a key precaution following past incidents in Basel and Landau.
Supplying regional heat networks
The project aims to supply district heating to the municipality of Graben-Neudorf and the nearby city of Bruchsal, with discussions ongoing with other regional utilities. Additional drilling is being planned for Dettenheim, just a few kilometres away, once regulatory conditions are met.
If progress continues as planned, a second production well could follow in 2026, depending on the availability of specialised drilling rigs in Europe. At around 3,600 metres depth and more than 200 °C, Graben-Neudorf is considered Germany’s hottest known thermal water reservoir.
To handle these temperatures, Deutsche Erdwärme installed heat-resistant downhole equipment not part of the original design. The company targets commercial heat extraction by 2029, alongside the planned construction of a geothermal power plant on the drilling site.
See previous coverage of the project on ThinkGeoEnergy here.
Source: our German partner website TiefeGeothermie
