Lower Saxony, the German state that finds itself in the north-western part of the country, has a rich history in drilling and coring. But until recently, activities on that front were exclusively centred around oil and gas. No surprise; the state hosts the majority of oil and gas fields in Germany and therefore, places like Celle, Lingen and Hannover have a significant oil industry presence.
However, that picture is changing, with many fields being decommissioned, combined with limited additional exploration potential and a political climate that is not favourable to oil and gas exploration either.
In that light, with the presence of a drilling industry and the associated service sector, it is a little surprising in some ways that it took until this month that the first “core for a future geothermal doublet” was cut in Lower Saxony. The area surely has potential, especially in the Triassic Rhaetian sandstone, which is a target in successful geothermal projects further east in Germany and in Denmark as well. For instance, Innargi’s flagship project in Aarhus targets the Triassic Rhaetian sandstone to supply the town with geothermal heat.
Strictly speaking, it is not the first core cut for a geothermal project though. In 2009, a deep borehole was drilled in front of the main office tower of the Geozentrum Hannover (BGR), with the aim to test the deep geothermal potential of the Lower Triassic Detfurth Sandstone at around 3,700 m. However, the project was a failure as the sandstone was unproductive, and following stimulation the borehole completely clogged up with halite cement.
The core that was now acquired is not from such a great depth. The Rhaetian sandstone was found at around 2,500 m. With a first run of core measurements indicating a >800 mD permeability, and a series of successful hydraulic tests, the properties of the reservoir also look favourable. From a total of 107 m cut core with a recovery of 98.6%, 44 m of Rhaetian sandstone was sampled. The core will now be investigated in more detail.
The project was carried out under the framework of the DemoCELL R&D project, which is funded by the Federal Ministry of Economic Affairs and Energy. Partners are Baker Hughes INTEQ GmbH and the University of Göttingen.
The drilling location is situated near the village of Ahnsbeck, just east of Celle. It is part of a geothermal exploration licence that was awarded to Baker Hughes INTEQ in 2023. Several other licences exist in Lower Saxony, but this is the first that has now progressed with putting some pipe in the ground. It is anticipated that the energy will be used for local heating purposes.
