By Peter Malin, SMU Adjunct Faculty
Peter Malin, an Adjunct Faculty in the SMU Huffington Department of Earth Sciences, provided this update on the st1 Deep Heat project in Espoo, Finland. Peter’s company Advanced Seismic Instrumentation & Research (ASIR) is providing seismic monitoring for the project.
Stimulation of the 6.4 km OTN-III well at the st1 Deep Heat project in Espoo, Finland began on June 4, 2018 and continues to the present time. There are 5 stages of packed-off, ball-operated hydraulic-stimulation equipment along the uncased bottom 750 m of the well. About 10,000 cubic meters of drinking-quality water have been injected via 3 of the 5 stages, with pumping currently occurring on stage 4. The engineering calculations provide a target volume of 18,000 cubic meters of water across the five stages for an economic return.
Near-real time seismic analysis has been provided by ASIR 24 hours a day 7 days a week during stimulation. As required by the public safety Traffic Light System (TLS), the turnaround on M>1.2 events is 5 minutes.
As has been seen at other Enhanced Geothermal System projects, there has been a large amount of microearthquake activity during stimulation. There have been about 15,000 events at magnitudes below M0. The ASIR team has determined locations for about 5,000 events. Most of these events fell within the green protocol in the TLS, i.e. <M1.2. There have been ~17 events which triggered the amber level with 1.2<M<1.8. These events resulted in a “Notify and Continue” response according to the TLS protocol.
By monitoring the seismic activity so closely, and by providing detailed location data so quickly, the teams are able to adjust stimulation pressures and flow-rates as stimulation occurs, thus avoiding (so far) any red events of >M2.1 which would result in “Stop and Notify, Resume Only if Permissible” on the TLS protocol.
Stimulation is expected to continue for several more weeks.
Along with the 24/7 work at OTN-III there has been time for celebration as project manager Tero Saarno got married in early June.