Work to start on permanent closure of geothermal borehole in Basel, Switzerland
The geothermal borehole in Basel, Switzerland will soon be permanently sealed, thus closing the chapter on one of the most infamous geothermal projects.
Energy company Industrielle Werke Basel (IWB) will soon be starting the work to permanently close the geothermal borehole in Basel, Switzerland. A re-entry and evaluation will first be done to evaluate how the well will be decommissioned and sealed.
The geothermal borehole referred to here was at the center of the induced seismicity incident that happened in Basel in the winter of 2006/2007. After triggering a 3.4-magnitude earthquake in December 2006 and more than 200 seismic events in the following months, the geothermal project was officially terminated in 2009. It remains one of the more infamous cautionary tales on geothermal reservoir stimulation, and has been the subject of several modeling and seismicity studies since then.
The first step of the decommissioning work will involve drilling through a blockage at a depth of 730 meters and subsequent cleaning up to 4700 meters. Well integrity will also be verified using ultrasonic sensors and wall thickness scanners. Information on the technical condition of the borehole will be the basis for how the well will be decommissioned and permanently sealed. A specialized drilling company from the Mitelland region will set up a mobile drilling rig to conduct the re-entry and borehole surveys.
The Swiss Seismological Service (SED) will monitor seismic activity during the upcoming work, although experts have stated that the activities are not expected to cause any tremors.
The closure of the geothermal well is physical, as well as symbolic. Induced seismicity in Basel has held back further geothermal development in Switzerland and other countries, and has been a source of anxieties and fears centered around reservoir stimulation. The industry has progressed vastly since then with more advanced stimulation methods, as well as safety measures such as seismic monitoring and traffic light systems.
With lessons learned in Basel already embedded indelibly into the future of geothermal, the decommissioning of the well in Basel is an important step towards closing this chapter.
Source: PrimeNews.ch and BazOnline