Geothermal energy project in Wilhelmsburg, Hamburg: Second borehole to gather more precise data about thermal water-bearing stratum 1,300 metres underground

1,300 metres below ground, the project team at HAMBURG ENERGIE Geothermie GmbH – a joint subsidiary of Hamburger Energiewerke and HAMBURG WASSER – has been able to detect thermal water in a rock stratum roughly 130 metres thick. The discovery was made by drilling laterally into the rock stratum. Initial production tests have confirmed the permeability of the sandstone, so the second drilling operation can now go ahead.

The second borehole will be sunk into the reservoir in a lateral direction at a depth of around 1,400 metres. Follow-up production tests will then provide reliable quantitative data about the geothermal potential of the thermal water in terms of its feed rate and temperature. These data are necessary in order to model the potential heat production for the Wilhelmsburg district of Hamburg. The water-bearing sandstone layer is approximately 45 million years old, and originally formed the beach area of the ‘young’ North Sea.

Michael Pollmann, State Councillor for the Environment, Climate, Energy and Agribusiness, says that ‘alongside wind and solar power, geothermal energy is an additional building block for a successful energy transition. During our first geothermal drilling operation in Wilhelmsburg, at medium depth, we came across a particularly promising thermal water source, which has given rise to a justified expectation that we can use the geothermal energy here – and perhaps elsewhere, too – for the energy transition. This now requires further investigations into the feed rate and temperature, which will be carried out with the aid of a second drilling operation. This second step in the pilot project to promote geothermal energy in Hamburg will supply us with additional data on the potential of this heat source in our city. To this extent, therefore, we have grounds to hope we can also use these possibilities to make ourselves independent from fossil fuels as speedily as possible.’

Kirsten Furst, CEO of Hamburger Energiewerke GmbH, adds: ‘Our exploratory drilling has enabled us to successfully demonstrate that thermal water, with the potential to produce geothermal energy, is flowing beneath the ground in Hamburg. This means that we have made a major step closer to our goal of producing local, environmentally friendly heat for Hamburg households that is capable of providing baseload power. Now it’s a question of safely sinking the second borehole into the depths and awaiting the results of the production tests.’

Ingo Hannemann, Spokesperson for HAMBURG WASSER management, says: ‘Our wide-ranging geological expertise, which we originally developed in connection with the drinking water supply system, and which we are now bringing to the project through our subsidiary CONSULAQUA, has provided the foundation for the research. Our exploitation of subterranean groundwater sources has made us well acquainted with the underground world, and we know how it can also be used for climate-friendly energy solutions. The research supporting the project has yielded important findings that are further improving our geological picture of the world below Hamburg and helping us to make better use of its potential as an energy source.’

If the production test is successful, then later on we also plan to feed the thermal water through the second borehole and feed it back to the reservoir in a closed circuit via the first borehole (injection borehole), which has already been sunk successfully. Generally speaking, at a depth of 1,300 metres we can expect a thermal water temperature somewhere in the range of 45–50 degrees Celsius. However, the specific temperature, which forms part of the ecological heating concept along with other factors such as the feed rate, must be determined for each location. At present, the project team is working on various technical solutions, which also take into account the use of heat pumps. The companies are optimistic that the final results can be presented this autumn.

The drilling operations are being supported by an extensive scientific research programme conducted by mesoTherm, in order to acquire data on the geothermal potential in the North German basin. In particular, as part of this rock samples several metres long, so-called ‘core samples’, are being taken from various rock strata. These have also demonstrated that we cannot expect to find any thermal water sources adequate for geothermal use in sandstone layers below 3,000 metres. At the Wilhelmsburg site, the sandstone stratum 1,300 metres down has turned out to be particularly rich. First of all, therefore, its geothermal potential has been investigated with the aid of core samples and hydraulic tests .

Inga Moeck, Professor of Geothermal Energy at the Georg August University in Göttingen and Head of the Department of Geothermal Energy at the Leibniz Institute for Applied Geophysics, is heading up the supporting scientific programme ‘mesoTherm’. She says: ‘Real discoveries are possible in the 21st century too. For example, through our drilling operations we have explored a newly discovered sandstone stratum that was formed 45 million years ago, and which today has extremely good properties for geothermal uses. We want to use the thermal water from this stratum to provide as many people as possible with renewable heat.’

The joint project mesoTherm is being undertaken under the leadership of the Geoscience Centre at the Georg August University in Göttingen, in collaboration with Geothermie Neubrandenburg GmbH (GTN) and the Leibnitz Institute for Applied Geophysics (LIAG) as an associated partner. Its core objective is to contribute to knowledge acquisition about the geothermal reservoir of North Germany and its potential use as an energy source.

Alongside wind and solar, geothermal energy is the third pillar of renewable energy. It is constant, and available locally. According to a study by the German Federal Environmental Agency, by 2050 deep geothermal energy will be able to contribute 118 terawatt hours per year to climate-neutral heat supply. 42 deep geothermal plants are in operation in Germany, with an installed heat output of roughly 350 megawatts. ‘Deep geothermal’ here refers to plants with a drilling depth over 400 metres and an average drilled depth of 2,500 metres.

The Hamburg geothermal energy project is part of the IW³ real-world laboratory (Integrated Heat Transition Wilhelmsburg), which aims at achieving virtually CO₂-free heat supply for the residential areas of Wilhelmsburg. The Federal Ministry for Economic Affairs and Climate Action (BMWK) is funding the undertaking with a total of around 22.5 million euros as a ‘living lab of the energy transition’, in order to support research and development in the field of forward-looking energy technologies. In particular, its aim is to reduce the risk associated with geothermal exploration through expanded knowledge.

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