In a paper published online in Seismological Research Letters on 5 February 2020 a team led by Seismologists from the Institute of Seismology at the University of Helsinki discusses observations obtained from a large network of seismic stations that was deployed during 2018 around the geothermal reservoir stimulation below the Aalto University campus in Otaniemi.
In June and July 2018 the operating St1 Deep Heat Oy company injected about 18,000 cubic meter of water at 6 km depth which caused many thousands of small earthquakes. The earthquake fractures reaching at most the meter scale underpin the concept of the Enhanced Geothermal System because they enable an efficient water circulation and thus heat exchange.
This uneven spatial distribution of the disturbances is controlled by the so-called source mechanism-the orientation of the activated fracture and the direction of the earthquake slip motion-of the largest earthquakes, which causes some areas to be more affected than others.
A second borehole is currently being drilled, and a smaller stimulation is planned for this spring to complete the circulation system. The plant is intended to operate for a few decades. Small earthquakes are expected during the forthcoming injection, and may also occur during later operating stages.
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Hillers, G., T. A. T. Vuorinen, M. R. Uski, J. T. Kortström, P. B. Mäntyniemi, T. Tiira, P. E. Malin, and T. Saarno (2020). The 2018 Geothermal Reservoir Stimulation in Espoo/Helsinki, Southern Finland: Seismic Network Anatomy and Data Features, Seismol. Res. Lett., doi: 10.1785/0220190253.
From the Global Geothermal News archives:
Hillers, G., T. A. T. Vuorinen, M. R. Uski, J. T. Kortström, P. B. Mäntyniemi, T. Tiira, P. E. Malin, and T. Saarno (2020). The 2018 Geothermal Reservoir Stimulation in Espoo/Helsinki, Southern Finland: Seismic Network Anatomy and Data Features, Seismol. Res. Lett., doi: 10.1785/0220190253.
From the Global Geothermal News archives:
- Monday, December 9, 2019 - Finland: Helsinki Utility to Start Exploration for Deep Geothermal District Heating Resource
- Tuesday, September 3, 2019 - Finland: Drilling at 40 MWth Espoo Geothermal District Heating Project Reaches Final Phase
- Friday, February 15, 2019 - Finland: How the 15,000 Foot Deep Wells At the Espoo Geothermal District Heating Project Were Drilled
- Tuesday, July 24, 2018 - Finland: Stimulation Begins at at the Espoo Geothermal Deep Heat Project
