In a recent statement on LinkedIn, geothermal exploration and development company Innargi announced that its flagship project in Aarhus, Denmark, will be developed differently from what was originally foreseen. Where the idea was to build seven production facilities with associated wells to supply around 20% of the city’s heat demand, now the plan is to only have three production sites in the north of the city.
At the same time, the company made clear that they will maintain the same energy output of 110 MWth.
This made me wonder, how does that work? Assuming that fewer wells will be drilled, how would it be possible to secure the same energy output? Have the test results of the three wells drilled so far been so much better than foreseen? I asked a few questions along these lines, to which the company responded.
When the first plans for the project were announced in 2022, 17 wells were planned. That number will now come down. “At this point, we have not concluded the total number of wells we will drill across the city,” a company spokesperson wrote. “We are still working on the new development plan and are therefore still designing the layout of wells depending on what we know about the subsurface now.” However, the person added that it is expected fewer wells will be drilled than the 17 originally planned.
On top of that comes the well that was drilled in the south of the city where the company did not find the reservoir characteristics they expected in the Triassic Gassum Formation. The press release clearly stated that it is in the north of the city where the three production sites will be located. In other words, the well that was drilled in the south will unlikely be part of the development plan and will therefore be a loss to the project. “Decommissioning a well is, of course, a cost that affects the project’s economy. But we have planned for the costs associated with understanding the subsurface in Aarhus and consider this an important step to reduce the subsurface risk for future drilling in Aarhus,” the spokesperson said.
Innargi was unable to share test results of the three wells that were drilled so far, as they are still working on finalising the development concept.
What to make of all this? First of all, Aarhus is still a flagship project given the size of the development, even when the number of production locations has now been reduced to three. However, reflecting on the information received, I find it hard to see how the company will be able to deliver the same amount of thermal energy when drilling fewer wells. In fact, there is an indication in an earlier company announcement that hints towards other ways to “compensate” for the loss in geothermal energy production; heat pumps.
In the LinkedIn post, the company celebrates the arrival of heat pumps at one of the Aarhus production sites. This is what the post said: “In Aarhus, the natural geothermal heat from beneath our feet is approximately 70°C, but in Kredsløb’s district heating grid they need to receive temperatures of 80°C. That’s where the heat pump steps in. It boosts the energy extraction and raises the temperature, unlocking the full potential of geothermal. In fact, thanks to heat pumps, we can recover up to 50% more energy than we would from just the first heat exchange alone.”
To me, it seems logical that the ultimate energy output of the project as a whole is measured only after the fluids exit the production site, so after the heat pump cycle. That means there is flexibility when it comes to how much geothermal energy is produced; if it is less than foreseen, the heat pumps just need to work a little harder. Even though Innargi did not confirm this to be the case, it is my take on why the same level of energy output can be maintained. I guess the costs of this are more manageable than drilling more wells, which is supported by a comment from somebody I recently spoke to and who was directly involved in drilling the wells: “The financial scrutiny was significant, to the point that I felt nothing could go wrong.”
In other words, Aarhus is still an important geothermal project, but it looks likely that it has become a little less geothermal than initially planned.
