Induced seismicity is a phenomenon that is not fully understood yet but is associated with geothermal systems and must be mitigated, especially in urban environments. Many geothermal projects have been paused due to such incidents in the past.
The new study that was carried out by a collaboration of commercial companies, universities and international scientists, attempted to control induced seismic incidents in the world's deepest geothermal well, located in Helsinki, the capital city of Finland. In particular, researchers developed a technique that prevented any occurrence of more that M2 seismic incidents.
The method includes the utilization of a traffic-light-style system that is capable of conducting almost real-time seismic monitoring warning the engineers to adjust the pressure and the pumping rates at the injection when its necessary. This ensured the successful control of the maximum magnitude of the induced earthquakes associated with the geothermal well.
"This feedback in near real-time was the key to success and allowed to deepen the understanding of the reservoir seismic response and the hydraulic energy release at depth, while ensuring promptness in the technical response to increased seismic activity," Prof. Georg Dresen, leader of the Geomechanics group at GFZ (German Research Centre for Geosciences), stated.
The so-called St1 Deep Heat Oy energy attempt is approved for additional development. A second well will be implemented and, afterwards, the geothermal project will operate normally to produce energy. The raw data of the case study cannot be used in geothermal wells with different geological background but the methodology applied should provide guidance for similar projects. "While the quantitative results successfully applied here to avoid larger seismic events are not directly transferrable to other tectonic settings, the methodology and concept we developed in our study can be useful to other EGS projects to limit the seismic risk and derive ad-hoc stimulation strategies," Grzegorz Kwiatek, a scientist at GFZ and lead-author of the study, said.