The realization of a high-temperature ATES in Berlin: from explorational drilling to implementation in Berlin-Adlershof

Concepts for achieving sustainable energy provision in urban areas require also an appropriate exploration concept for a succesful planning of a possible site-development. Geophysical exploration data and deep reaching boreholes are commonly rare in such areas. In Berlin, Germany, the German Research Centre for Geosciences drilled a research borehole to investigate the usability of Mesozoic aquifers as underground thermal storage reservoirs, the Gt BtrKoe 1/2021 borehole in Berlin-Adlershof. The information gained from this borehole provides new structural data and encounters several Mesozoic potentially ATES aquifers. The general depth of those aquifers are largely determined by the ascent and location of the underlying Permian salt structure. The research well was completely cored from a depth of 210 m (close to the top of pre-Tertiary) to the final depth of the well at 456 m. Based on an in-depth characterization of the cores that included also geophysical measurements on cores (like gamma-ray, bulk density, thermal properties, and p-XRF) and a detailed geological description, the porosity, permeability, and lithological heterogeneity of the drilled succession was evaluated and integrated in a 3D geological model. In the cored borehole section, several promising sandy reservoir sections were drilled, with a main storage reservoir in the Lower Jurassic Hettangian at a depth of 360–400 m. The sandstone is very fine grained and only weakly consolidated, showing porosities of 25–30% and permeabilities of more than 1 Darcy (> 10-12 m²). A first simulation allows for a successful integration of an ATES using this horizon at this site. The simulation is based on the seasonal provision of 35 GWh of storeable heat provided from a wood-fired combined heat and power plant  for a time period of 4 months with a temperature of 90°C, which is stored in the 24°C warm sandstone reservoir. The simulation shows that it will take about two years of operation to reach the full storage potential of the reservoir. Based on the findings, a real ATES will be established at the site, allowing to study in detail possible rock-fluid interactions and the overall performance of the system. The site activities are funded by the BMWK (FKZ 03EE4007 and FKZ 03EWR022C) and the EU project PUSH-IT (https://www.push-it-thermalstorage.eu/).