The Koillismaa Deep Hole – A Multidimensional Investigation

“This will be the deepest drilling intended for research in Finland” tells the project manager, Aleksi Salo from the Geological survey of Finland (GTK).

GTK will start to drill a three-kilometre-deep hole in southern Kuusamo with the goal of researching the bedrock of Koillismaa at depth. Within the Finnish context, this unique deep hole will create a special test environment for bedrock research. The research project is a multidimensional RDI investment, which, beyond deep bedrock research and the development of survey technology, will also benefit research related to mineral systems and 3D modelling, the utilization of geothermal energy, deep groundwater and bedrock stability.

The project started in September and, according to the plan, drilling will commence on 20 September. This year, the goal will be to drill to a depth of 2500 metres, and in the next year it will be continued to 3000 metres. At these depths, drilling is very challenging. After 2000 metres, it is a step into the unknown, both technically and geologically. Drilling will be carried out by the Arctic Drilling Company from Rovaniemi. For the drilling, the company will use a rig that they have designed and built themselves.

“This type of drilling equipment has not been used in Europe before in order to drill such a deep hole,” according to the Head of Unit (GTK), Mr. Pasi Heino.

Diverse research

Southern Kuusamo was chosen as the target for the deep drilling. The region has been researched in several projects since the 1970s. Now, special interest has focused on an anomaly located deep within the bedrock that was revealed by geophysical data, the cause of which is unknown. This almost 60-kilometre-long, east–west-trending anomaly, located at a depth of 1 to 3 kilometres, has been the subject of several interpretations and models. Such models can now be tested by deep drilling, and it will be possible to obtain new information that can be applied in research on targets located deep within the bedrock and in regional 3D bedrock modelling. This deep hole will lead geophysical and geological research to a completely new depth level in a region where this has not previously been possible.

Geothermal energy, and especially the energy exploitable from a depth of 1 to 3 km, is a subject of increasing interest, but there is still limited data on this. The hole to be drilled now will be the first one to this depth from which information on the geothermal energy potential of northern Finland will be obtained.

Deep bedrock groundwater and bedrock stability will be also investigated within the Koillismaa Deep Hole Project. Bedrock groundwater is usually salty at depth and can contain dissolved gasses. This is challenging from the point of view of construction into the bedrock. Bedrock disturbances and their recovery will be also topics of research. The Koillismaa region is the most active earthquake zone in Finland.

The environmental impact of the drill site will be monitored during the drilling project. Already before the beginning of drilling, GTK’s researchers have started to map the background geochemical concentrations of soil and water in the nearby area. Drilling will be performed with a permit granted by a local landowner.

“Working close to a Natura 2000 area establishes its own challenges, which will be tackled through strict monitoring and sampling” reveals the Project Leader, Mr. Aleksi Salo.

Significant investment

“For us, the Deep Hole is a very significant RDI investment and a multidimensional ensemble, which will involve the participation of several of GTK’s units. Research, development and innovations will be built up around the project together with our partners and clients,” tells the Director, Mr. Olli Breilin from GTK.

For this and the next year, GTK’s investment budget for the project is 860 000 euros. The project will offer a possibility to develop the current equipment of GTK and its partners to correspond to the needs of deep hole research and new types of research technology within deep hole conditions.

Additional information:
Project Leader Aleksi Salo,, f. 0295033425
Head of Unit Pasi Heino,, f. 0295033440

Geophycical model of the anomaly


The drilling site location.

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