Paving the way for deep geothermal energy

Around a third of the energy consumed in Germany is used for heating and hot water. Three quarters of this heat is generated using imported fossil fuels, which are becoming increasingly expensive due to the influence of unstable supply relationships in the medium term. Climate change caused by combustion gases is likewise prompting us to have a rethink and act swiftly.

Local politicians who recognise that the earth can provide us with an unlimited supply of heat can be climate-saving trailblazers and can guarantee security of supply. It’s simply a question of exploiting this supply – in the form of deep geothermal energy.

The German government now recognises this too – according to the Federal Ministry for Economic Affairs and Climate Action, 50 per cent of the nation’s heat supply is to be generated climate-neutrally by 2030. ‘The Climate Action Status report of January 2022 therefore contains the specific target of developing geothermal potential of 10 TWh by 2030 as far as this is possible, and to thus multiply the amount fed in from these sources to the heat networks by a factor of ten. In order to do this, we want to initiate at least 100 additional geothermal projects by 2030, connect them to heat networks and use the geothermal energy in residential buildings, neighbourhoods and industrial processes. Regions where geothermal energy is an appropriate source are therefore to be identified in an exploration campaign, and the information is to be provided to the municipalities. Throughout the process, consideration is to be given to all the questions of safety and environmental protection,’ says the ministry.

From a political and economic perspective, geothermal energy is an important component with which to improve the ability of municipalities and businesses to compete, thereby safeguarding the industrial future of Germany.

Experience shows consistently positive outcomes.

The city of Munich can already supply 40 per cent of its households with district heating via an approximately 900-kilometre-long network. Munich’s municipal utilities are now aiming to do without fossil fuels entirely. The Münchner Merkur newspaper reports that ‘the geothermal power plant in the district of Sendling alone provides enough energy for 80,000 inhabitants. Based on this impressive experience, the municipal utility company Stadtwerke München (SWM) wishes to additionally tap geothermal energy with thermal output of up to 450 megawatts by 2030 to cover the majority of its district heating needs. And the city in Bavaria is confident that the planned investments of around one billion euros will be lucrative in the long term.

Deep geothermal energy is an important component in converting Germany’s energy supply.

The basic principle is simple. You drill two holes. You then withdraw warm/hot water from one of these holes in the ground and feed the cooled water back via the other hole. The earth itself sees to the reheating of the water. Or to use the words of the Leibniz Institute for Applied Geophysics (LIAG): ‘Geothermal energy is a form of renewable energy from the geological substratum. It feeds on the earth’s natural flow of heat and the thermal properties of the earth’s crust. […] Deep geothermal energy is associated with the use of hydrothermal doublets that utilise thermal water for energy. With a drilling doublet, one drill hole (production well) is used to source energy and the other (injection well) is used to maintain sustainability.’

Large heat pumps are used to extract the heat from the water deep in the earth, with this then used to heat the district heating water. In this way, thermal water at temperatures of 40 to 70°C can be exploited for heat networks. In Germany, reservoir temperatures in this range can be found at depths of 400 to 2,500 metres. This is known as mid-depth geothermal energy.

Starting at depths of approximately 3,000 metres, where deep geothermal energy begins, the thermal water is so hot that heat pumps are no longer needed. This is when things get really interesting as no power is needed to run the heat pumps – and you can even generate power.

With geothermal energy, municipalities bring huge potential to the light of day.

If you think that drilling two holes is all it takes, then think again, as there are risks involved. A doublet alone, like the one in Munich, can cost upward of 12 million euros. Finding out whether the substratum is even suitable for the extraction of geothermal energy is therefore essential. Drilling risks due to unexpectedly complex geological formations and, in particular, the potential discovery risk illustrate that drilling projects which lack expert preparation are indeed a very chancy idea.

Having the experts at DMT conduct a detailed exploration before getting down to drilling would be a much safer option. The extensive seismic readings call for an interdisciplinary team of engineers consisting at the very least of experts in the fields of geophysics, geology and geodesy.

Qualified 3D surveys are still needed across large swathes of Germany.

Germany’s substratum has been extensively charted in the past (up to approximately 40 per cent), but this data is now between 50 and 75 years old. It focuses in particular on oil and gas deposits in rural areas and is therefore not adequate for qualified assertions regarding the prospects of discovering geothermal energy. To collect the data needed to develop a concrete cogeneration plant project in urban settings, there is now de facto no alternative to non-destructive 3D reflection seismics – depending on the exploration depth, different signal generator technologies such as DMT’s special seismic vibrator trucks are used for what’s known as vibroseismics. In the case of transition zone (TZ) measurements in shallow water areas, airguns are used as the seismic source, with the data being registered via Baycable systems. Further methods can be applied if needed, such as electromagnetic, magnetic and geophysical potential methods as well as borehole or airborne geophysics.


‘It goes without saying that the most stringent QHSE standards have to be observed when performing such surveys’ Dombrowski emphasises. ‘Certification in accordance with ISO 9001, ISO 14001, ISO 45001 (formerly OHSAS 18001) and SCCP has to be submitted and the IAGC’s guidelines have to be observed,’ adds Lehmann.

The readings then need to be be processed and geologically interpreted. Meaningful three-dimensional images of the substratum can then be generated using the appropriate data processing method such as pre-stack time migration (PSTM), pre-stack depth migration (PSDM) and common reflection surface (CRS) processing.

Things can and must now progress quickly.

Once the policymakers have cleared the way for the swift development of geothermal power plants, which now looks likely, a geothermal project can finally be realised. And what once took eight to ten years can now be realised in two to three years. In the opinion of DMT, the key issues are the comprehensive exploration of Germany’s substratum at depths ranging from 400 to 5,000 metres, the acceleration of requests for approval, exploration risk insurance and the standardisation of geothermal plant engineering.

Swift development in the direction of the energy transition will be driven not only by the municipal utilities, but, in the area of geothermal energy use, also by industrial companies, real estate developers and operators, and agricultural businesses. They can expect local solutions that meet their specific needs based on entirely new time frames – DMT’s geothermal energy project managers can already report successes with all kinds of customers, from greenhouse operators to paper factories.

DMT is here to offer advice at every stage of a geothermal energy project, from cost-effectiveness analysis, exploration, financing, the approval procedures and drilling planning to selecting the borehole pump and then planning and constructing a plant and connecting it to a district heating network. Upon request, DMT can coordinate all the technical disciplines together with TÜV NORD GROUP and then hand over a turnkey plant. Here, transparency vis-à-vis the public should not be underestimated as it leads to broad societal acceptance of geothermal energy projects. That’s Engineering Performance.

In spite of everything, there is unfortunately still a slight snag as the German government has not yet reached a decision regarding exploration risk insurance, which is needed in order to initiate and realise geothermal energy projects throughout the country and to prevent the municipalities from bearing the financial risks alone. A little political pressure from the municipalities could therefore prompt the federal states and the German government to reach a decision regarding this important support measure more quickly. The good news is that there are already promotional programmes from KfW (German  development bank) with subsidies for plants, drilling costs and additional expenses, to take the strain off the municipal coffers. DMT can act as an advisor here too.

The space needed for a geothermal energy plant is approximately the size of a football pitch. An area of this size should be available in the majority of German towns and cities.

Something a little more difficult than finding the space for a plant is securing the acceptance of the local residents for such new measures, with the main concerns being construction and operation noise. Fortunately, modern drilling units are equipped with electric drives and additional soundproofing measures during the construction stage can reduce the noise pollution. At the operational stage, the choice and the arrangement of the fans used to cool the power plant are important for the successful avoidance of noise. Here, too, additional soundproofing measures can be implemented for even quieter operation, if necessary. This boosts acceptance, as does the argument of considerably higher price stability, as the heat taken from the earth beneath us is not subject to the price fluctuations in the commodity markets. That said, possible concerns of local residents are taken into account by DMT from the early during the planning stage, in order to increase the long-lasting and widespread support for geothermal energy.

From a political and economic perspective therefore, exploration for geothermal energy is the right decision and leads to the climate-neutral future viability of businesses and municipalities.

DMT is happy to advise you right from the very first step. Simply get in touch.

The project development stages

Stage 1: preparation

  • Data research and processing
  • Regional/national resource model
  • Improvement of the data if needed, 2D seismics
  • Initial assessment of the site resources

Stage 2: overground exploration

  • 3D seismic exploration
  • HEATFLOW simulation
  • Local 3D reservoir model
  • Selection of drilling site
  • Bore path planning
  • Probability-of-success study

Stage 3: underground exploration

  • Drilling planning and preparation
  • Seismological monitoring
  • Drilling and borehole measurements
  • Discoverability (geothermal parameters at least as expected)
  • Cost-effectiveness

Stage 4: construction, network connection, operation

  • Plant planning and design
  • Plant engineering construction and optimisation
  • Network integration
  • Trial operation, operation

DMT’s advisory services and service portfolio along the geothermal energy value chain

Project initiation

  • Preliminary assessment of regulations, site, technology, market
  • Benefit and risk structure
  • Cost-effectiveness analysis
  • Planning of project structure in subsequent stages

Site exploration

  • Permits and approvals
  • Seismic exploration
  • Geophysical surveys
  • Drilling, extraction and heat utilisation feasibility studies
  • Reservoir simulation, extraction forecast
  • Probability-of-success study
  • Heating plant site suitability tests
  • Environmental impact assessment
  • Drilling operation plans
  • Drilling site construction and drilling
  • Circulation tests

Construction, expansion, operation

  • Applications for approval
  • Operation plans and approval procedures
  • Building and plant planning
  • Pipeline construction
  • Measurement technology
  • Network connection
  • Start-up
  • Maintenance
  • Capacity expansion
  • Plant expansion

Why DMT is a recommended consultant for geothermal power plant development

  • Single point of solution: access to a multidisciplinary team encompassing all the areas of relevance to geothermal energy
  • DMT as part of the TÜV NORD GROUP: a high standing with the public and the authorities
  • Flexible and short-notice response times
  • Services provided from Germany, with German expertise
  • DMT is the market leader in Germany in geothermal exploration
  • Access to data pools (such as databases on geothermal energy, oil, gas, hard coal and abandoned mines, to name but a few) and detailed knowledge of the local geology
  • Daily dealings with all the laws, regulations, ordinances, guidelines, approval procedures, etc. of relevance to geothermal energy (examples: Federal Mining Act [BBergG], Federal Water Act [WHG], Geological Data Act [GeolDG], Renewable Energy Sources Act [EEG], Energy Industry Act [EnWG], Federal Immission Control Act [BImSchG])
  • Excellent network of stakeholders and partners (geological services, mining authorities, research institutes, municipalities and towns/cities, energy utilities, project developers, environmental authorities, drilling companies, plant engineering)
  • DMT has seismic equipment for all geographical conditions (inner cities, land, sea, river crossings, bogs, etc.)

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