In this data publication field data and measurements of the Gt BTrKoe 1a/2024 sidetrack, drilled by the GFZ Helmholtz Centre for Geosciences in Berlin, Germany, are reported. Moreover, additional grain-size analysis on core material of the main well (Gt BTrKoe 1/2021) are provided. The main borehole Gt BTrKoe 1/2021 was drilled in 2021 in Adlershof on the compound of the BTB Blockheizkraftwerks-Träger- und Betreibergesellschaft mbH Berlin (see data publication of Norden et al., 2023), aiming to shed light on the frame conditions of geological aquifer thermal energy storage (ATES) and heat utilization Berlin and to support ATES development in urban areas in general and minimize explorational risks for future site developments in the SE of Berlin. The borehole encountered several Mesozoic aquifers in depths of up to 500 m, representing promising sandy reservoir sections for ATES application (Norden et al., 2023; Norden et al., 2024). The drilling reached a final depth of 456 m below ground level (b.g.l.) when the terrestrial (arid) clayey Keuper sediments of the Exter Formation (Upper German Triassic) were cored. Based on the findings of the borehole, a reservoir in the Lower Jurassic Hettangian at depths of 360–400 m was selected for further testing. However, due to a technical failure during the cementation of the casing, the lower part of the borehole and the filter screens were cemented up to 300 m measured depth (MD) b.g.l., losing the access to the reservoir. Because measures for re-opening the cemented part of the well were not successful, it was decided to drill a sidetrack out of the existing well path.
This data publication comprises the main drilling and deviation data of this sidetrack (Gt BTrKoe 1a/2024) and the geological and geochemical characterization of the borehole cuttings and the data of the commercial geophysical logging. After drilling, the sidetrack was completed successfully. This time, setting of casing, filter screens, fiber-optic monitoring cables, and the cementation of the casing went well. The measured fiber-optic temperature data from distributed temperature sensing (DTS) collected during cementing and during the initial filter development of the sidetrack conducted in early September 2024, together with other monitored data such as geochemistry and hydraulic (pressure, flow rate), are also provided in this data set. Finally, a conventional wireline temperature logging was performed by GFZ on the 14th of April 2025 to record thermally undisturbed formation temperatures.
The DFG funded DeepEarthshape project within the SPP1803 EarthShape (second phase) combines several geoscientific methods and approaches to study the weathering zone in detail in dependence of climate conditions. Projects of the first phase have shown that the weathering zone is much deeper than expected, so that the weathering front was never encountered in the excavated soil pits. At depth of 1 – 2 m appreciable amounts of microbial biomass and DNA counts were encountered. It was further found that bacteria and archaea colonizing rock surfaces are close relatives to those from deeper soil zones. Because we do not know a) the depth of weathering; b) the process advancing it; c) whether this advance is driven by water, gases, and/or biological activity and concentrated along faults; d) whether this zone presents a habitat and interacts with the surface biosphere, we have designed a drilling campaign at all four study sites for joint geochemical, biogeochemical and microbiological exploration and a geophysical campaign for imaging the depth and physical properties of the critical zone. The principle hypotheses of the DeepEarthshape projects are: 1) The advance of the weathering front at depth is a recent process that is linked to climate and coupled with erosion at the surface through a biogeochemical feedback 2) Microbial activity in the deep regolith that advances weathering, is fuelled by young organic matter. The four study sites are distributed along the coast of Chile to have a similar geological setting but different climatic conditions.
Here we present the logging data of the first geophysical borehole survey which took place at the Private Reserve Santa Gracia, 40 km NE of La Serena (Coquimbo Region, Chile). The data were acquired on the 2nd of April 2019. The borehole logging was conducted by COMPROBE. The vertical borehole reached down to 87.2 m depth and had a diameter (PQ) of 83.5 mm.
The acoustic televiewer data are freely accessible now in .dlis and PDF formats. The original data files are embargoed until 30 June 2022 and will be accessible via this page afterwards.