The Gt BTrKoe 1/2021 borehole was drilled in the framework of a research project called GeoFern, funded by the German Ministry for Economic Affairs and Climate Action under the grant number 03EE4007. The overall objective of this research project was to support the development of the geothermal heat utilization for urban areas. Therefore, the integration of reservoir utilization concepts into heat supply systems need to be studied. The GeoFern project aimed to contribute to the knowledge on geological structure and the lithological composition of the subsurface to minimize the explorational risks for future site developments in SE Berlin, Germany. It focused on the exploration of possible Mesozoic aquifers, suitable for aquifer thermal energy storage (ATES) in depths of up to 500 m. As stopping criteria for drilling, the presence of terrestrial (arid) clayey Keuper sediments of the Exter Formation (Upper German Triassic) were defined.

In this data publication we provide the results of the investigations and measurements conducted on site in the field laboratory as well as the open-hole geophysical well-logging data of the Gt BTrKoe 1/2021 borehole acquired by a commercial contractor. In addition, a temperature log of the borehole, measured by the GFZ about two months after the end of drilling activities, is part of this data publication.

The drilling of the Gt BTrKoe 1/2021 borehole started at the 15th of November 2021 with the setting of the conductor pipe and reached its final depth of 456 m in Triassic sediments on the 19th of December 2021. The drilling was conducted in two main sections using two different technologies. For the upper section, covering Cenozoic sediments and reaching a depth of 211 m, reverse drilling technology was used. This section comprises the Quaternary to Tertiary groundwater system and the Tertiary “Rupelton” (Oligocene, Rupelian). The latter represents an about 100 m thick clayey succession that do act as a regional aquitard, separating the deeper saline groundwater systems from the upper utilized (freshwater) groundwater levels. After setting and cementing of the casing, the borehole was further deepened by using conventional Rotary drilling technology. Due to the lack of knowledge on the geological situation of the pre-Cenozoic strata before the drilling, this section represents the most relevant part for answering the research goals of the project. In order to allow the most accurate description and characterization of the drilled strata, this section was completely cored using wireline coring equipment with 3-m core barrels. In total, 90 core runs were conducted and 197.4 m of cores retrieved, showing a core recovery factor of 81%. The core show a mean core diameter of about 100 mm. The drilling was stopped after encountering the multicolored terrestrial playa sediments of the Upper Triassic in the last core run.

While the token cutting samples were not assigned with International Generic Sample Numbers (IGSN), the borehole (Norden, 2022) and all taken cores were registered with IGSNs.