St1's geothermal pilot project in Otaniemi, Espoo, progresses to the finalization of the heat wells

The final phase of drilling for the St1 geothermal pilot heating plant in Otaniemi has been successfully completed in March and two geothermal heat wells extending to a depth of more than 6 km are now ready. The water conducted between them, which naturally heats in the bedrock, is utilized in the production of district heating when the plant is completed. The plant's heat production is fed via heat exchangers into Fortum's district heating network and can cover up to 10% of the district heating needed in Espoo. The target schedule for the start of commissioning of the Otaniemi geothermal heating plant is October 2020.

Geothermal heat production that utilizes the heat of the bedrock is a new, emission-free form of energy production in Finland. It can significantly reduce not only CO2 emissions, but also small particulate emissions from traditional combustion heat production – i.e. improving urban air quality.

Now the Otaniemi geothermal pilot project has progressed to the finalization of the heat wells. First, hydraulic tests are performed, on the basis of which the need for so-called counter stimulation is found out. In practice, counter stimulation means that water is pumped into another deep heat well. This ensures that the water supplied to the system flows as well as possible in the rock fracture between the wells. Potential counter stimulation would begin in early May and last for about two weeks.

Noise nuisance possible in the vicinity in the coming weeks

The effects of the measures are closely monitored in co-operation with the Institute of Seismology of the University of Helsinki. A monitoring system has been set up for the project, which will enable hydraulic tests and stimulation to be carried out in a very controlled manner - without endangering people or property. A measurement network installed deep in the rock is used to monitor both the flow of water and the micro-earthquakes that the work steps are likely to cause deep in the bedrock. Micro-earthquakes may cause momentary sounds on the ground in nearby areas. Sound waves can also resonate in windows and structures, but they do not pose a danger to people or damage structures. Potential micro-earthquakes can occur at different times of the day with hydraulic tests, possible counter-stimulation and preparatory work in progress between weeks 17-20.

“We apologize already in advance for any noise nuisance caused by micro-earthquakes that may occur to residents in nearby areas during the finishing phase of the heat wells. This is an important, but time-limited, step in a unique project that, if successful, could revolutionize the way heat is produced in the Nordic countries and Europe more broadly, i.e. enable zero-emission district heating production”, says Matti Pentti, Director of St1 Oy, Heat from the Ground.

Further information:

St1 Oy, Matti Pentti, Director, Heat from the Ground, tel. +358 10 557 4119,

 St1 Nordic Oy is a Nordic energy Group whose vision is to be the leading producer and seller of CO2-aware energy. The Group researches and develops economically viable, environmentally sustainable energy solutions. St1 focuses on fuels marketing activities, oil refining and renewable energy solutions such as waste-based advanced ethanol fuels and industrial wind power. The Group has 1300 St1 and Shell branded retail stations in Finland, Sweden and Norway. Headquartered in Helsinki, St1 employs currently 770 people.

The St1 monitoring network detected 1.67 magnitudes micro-earthquake


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