Green Therma Selects H&P to Drill Denmark’s Longest Geothermal Well for Aalborg Heat4Ever Demonstration Denmark is moving from geothermal ambition to execution. Green Therma has selected Helmerich & Payne to drill the Heat4Ever demonstration well near Aalborg, a project that could become one of the country’s most technically ambitious geothermal developments and a meaningful test of closed-loop district heating. A milestone for Danish geothermal The Aalborg Heat4Ever project matters because it is designed to prove that geothermal heat can be delivered without relying on a natural hot-water reservoir. Instead of producing groundwater from a conventional geothermal field, the system uses a closed-loop pipe-in-pipe design that circulates the same fluid downhole, heats it in contact with hot rock, and returns it to the surface for district heating use. That distinction is important for Denmark, where district heating is already a major part of the energy system a...
Green Therma Selects H&P to Drill Denmark’s Longest Geothermal Well for Aalborg Heat4Ever Demonstration
Denmark is moving from geothermal ambition to execution. Green Therma has selected Helmerich & Payne to drill the Heat4Ever demonstration well near Aalborg, a project that could become one of the country’s most technically ambitious geothermal developments and a meaningful test of closed-loop district heating.
A milestone for Danish geothermal
The Aalborg Heat4Ever project matters because it is designed to prove that geothermal heat can be delivered without relying on a natural hot-water reservoir. Instead of producing groundwater from a conventional geothermal field, the system uses a closed-loop pipe-in-pipe design that circulates the same fluid downhole, heats it in contact with hot rock, and returns it to the surface for district heating use.
That distinction is important for Denmark, where district heating is already a major part of the energy system and where geothermal can provide steady thermal energy alongside wind and solar. The project is therefore not just a single well; it is a potential reference point for how deep geothermal heating could be deployed in more locations.
What Green Therma is building
Green Therma’s Heat4Ever concept is built around closed-loop geothermal heating rather than the more familiar hydrothermal model. The company’s DualVac approach uses vacuum insulation in a pipe-in-pipe configuration to reduce heat loss as fluid travels back to the surface, improving the efficiency of heat delivery into a district heating network.
This matters because geothermal systems become economically stronger when more of the heat gathered underground reaches the consumer. In a closed-loop design, the challenge is not finding a naturally flowing reservoir, but drilling deep enough and managing the well architecture so the system can extract useful heat from the surrounding rock.
Why the Aalborg site was chosen
The project is planned for Storvorde, near Aalborg, close to existing district heating infrastructure. That location reduces the need for expensive new heat transmission assets, which is critical for any project that hopes to deliver geothermal heat competitively to end users.
Aalborg Forsyning has described the site as a strategic fit for the demonstration, and the project has already advanced through key regulatory and development steps, including an exclusive geothermal exploration and extraction licence in the Aalborg area. The project also has a 30-year agreement to supply heat to Aalborg Forsyning, which gives it a real customer and a clear commercial use case.
The drilling challenge ahead
The planned well is expected to reach about 4 to 5 kilometres in depth, with a horizontal section of roughly 2 to 3 kilometres. That geometry makes it far more complex than a standard vertical well and places heavy demands on directional drilling, well stability, casing, cementing, and trajectory control.
The horizontal section is especially important because it increases the contact area between the well and the hot subsurface environment. The longer that heat-transfer section is, the better the chances of capturing enough thermal energy to support district heating, but drilling and completing such a well is still a major engineering challenge.
Why H&P matters
Selecting Helmerich & Payne signals that the project is moving into the operational phase. Green Therma needs a contractor with deep drilling experience, precision well control, and the ability to handle a technically demanding geothermal target, while H&P brings the execution capability needed to turn the concept into a physical well.
This kind of partnership is increasingly common in next-generation geothermal projects, where companies developing new heat or power concepts often rely on experienced drilling specialists from the oil and gas sector. In Aalborg, that combination could prove decisive because the success of the entire demonstration depends on getting the well drilled accurately and safely.
Why closed-loop geothermal is different
Closed-loop geothermal changes the development logic of the sector. Instead of asking where a sufficiently permeable reservoir exists, developers can focus on whether a location can be drilled deeply enough to access useful temperatures while keeping the loop sealed and efficient.
That does not remove geological risk, because rock temperature, thermal conductivity, depth, and drilling conditions still matter. But it does reduce dependence on the kind of natural reservoir conditions that have historically limited conventional geothermal projects in many regions.
The district heating opportunity
Denmark is a strong market for geothermal heat because district heating is already deeply embedded in the country’s energy infrastructure. That creates a practical route for geothermal projects, since heat can be delivered directly into an existing network rather than being converted into electricity first and then used for heating.
That direct-use model can be more efficient and more economically attractive for lower-temperature geothermal resources. It also fits a broader European trend: using geothermal as a reliable, always-available source of renewable heat for cities and towns.
Funding and timeline
The demonstration project has a total budget of about DKK 133 million, including DKK 84 million in support from Denmark’s Energy Technology Development and Demonstration Program. Materials are expected to arrive in autumn 2026, with drilling targeted for January 2027.
According to the project timeline, the drilling phase should take around three months, followed by installation of surface equipment and integration with the district heating network. If the schedule holds, 2027 will be the year the project shifts from planning into real operating data.
Why the project is closely watched
Heat4Ever is being watched because it could become an early proof point for closed-loop geothermal district heating in Europe. If it works as intended, the project would show that deep geothermal heat can be engineered, drilled, and delivered even without the conventional reservoir assumptions that have shaped the industry for decades.
That would be significant not only for Green Therma, but also for utilities, policymakers, and geothermal developers seeking scalable low-carbon heating options. In that sense, the well outside Aalborg is more than a demonstration; it is a test of whether a new geothermal model can move toward broader commercial use.
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Source : Green Therma
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