Geo-Energie Suisse succeeded in creating a permeable geothermal reservoir in the Gotthard mass granite at Zurich ETH’s Bedretto Laboratory, a breakthrough and technical proof for the company’s patented multi-stage geothermal stimulation concept.
In a breakthrough for deep geothermal, and announced today, Switzerland-based Geo-Energie Suisse (GES) announced that it has succeeded in obtaining technical proof of the company’s patented multi-stage stimulation concept. A successful demonstration took place at the Bedretto Underground laboratory for Geosciences and Geoenergy of the ETH Zurich in Canton Ticino at the end of 2020. Geo-Energie Suisse hopes the achievements in the Gotthard massif will give new impetus to the pilot project in Haute-Sorne (JU) and to production of electricity and heat from geothermal energy throughout Switzerland.
The potential of geothermal energy as a renewable and climate neutral energy source does not need to be questioned. The natural heat in the earth’s crust does not produce CO2 emissions and provides constant thermal energy that can be used for electricity production or directly as a heat source. In addition, geothermal power generation has a negligible impact on the landscape, as it takes up very little land area. At present, however, there is one major challenge that must be overcome if geothermal is to be used economically as a renewable power source on a large scale: that of reliable and location independent development outside of geothermal hotspots, such as in Iceland, Indonesia or New Zealand.
With support from the Werner Siemens Foundation, ETH Zurich has built a new research infrastructure to investigate these questions. At the «Bedretto Underground Laboratory for Geoenergy», ETH Zurich studies in close collaboration with national and international partners the techniques and procedures for safe, efficient and sustainable use of geothermal. GES demonstrates as an external partner at the Bedretto Laboratory within the framework of DESTRESS, ZoDrEx and IASS projecting how heat exchangers can be carefully made underground.
Switzerland’s first evidence of a multi-stage stimulation concept patented by GES.
In Basel, in 2006, efforts were made to create a geothermal reservoir in one step with a vertical open borehole. However, hydraulic stimulation triggers an earthquake which is unacceptable. In response to the technical challenges of developing a safe reservoir, Geo-Energie Suisse AG developed a multi-stage stimulation concept and patented it for Switzerland in 2012. The concept provides for the formation of a permeable reservoir in a crystalline basement at a depth of 4. to 5 kilometers required for electricity production. through targeted water injection. To minimize the associated seismic risk, hydraulic stimulation is carried out in sections and in small, staggered steps. A reservoir section sequence is made along a horizontal borehole. This is connected to the second horizontally deviated borehole. The result is a large underground heat exchanger that can be used to generate electricity and extract heat in geothermal power plants. Geo-Energie Suisse has now been able to prove for the first time that this multi-stage stimulation concept works in Switzerland, at the Bedretto ETH Zurich Laboratory.
A milestone in the use of deep geothermal energy in Switzerland
“We managed to increase the permeability by a factor of 10 to 100 in compact granite from the Gotthard mass with the aid of targeted stimulation, and in measuring and controlling the microseismicity required for the development of the gaps,” explains Dr Peter Meier, CEO of Geo-Energie Suisse AG, and added : «I believe that this breakthrough is a significant milestone on the way to Switzerland’s first geothermal power plant. On the one hand, this is because the permeability achieved in one of the two boreholes corresponds to the transmissivity required for economic applications. On the other hand, and this is central, the microseismicity associated with stimulation yields a maximum magnitude of -1.8 Mw on the Richter scale which is about 1 million times smaller than in Basel. »GES achieved this success within the framework of demonstration and innovation projects with the participation of national and international partners (see text box). The next step is a scientific evaluation by ETH Zurich, EPFL and the University of Neuchâtel. The evaluation will form the basis for a future, detailed stimulation program of the Geo-Energie Suisse pilot project at the site in Haute-Sorne in the canton of Jura. Another interim objective of the GES that was successfully achieved was the qualification and validation of any newly developed technical components relevant for safety or more economically for the construction of deep geothermal reservoirs. Further qualification and validation work is planned for 2021, 2022 and 2023.
International cooperation is the key to reliability and further development of innovation
As an industrial partner, GES will also validate findings obtained at the Bedretto Laboratory at the US FORGE Utah (Frontier Observatory for Research in Geothermal Energy) test site in the high temperature range. The focus lies in using seismic sensors to control induced microseismicity and direct development – a key element for safe stimulation underground. This is another step to increase the chances of success and safety of Switzerland’s first deep geothermal pilot project at the Haute-Sorne in the canton of Jura, and to promote the deep use of geothermal energy in Switzerland.
The achievements at Bedretto brought a new impetus to the pilot project in Haute-Sorne
At the end of June 2020, the Swiss Federal Energy Office increased exploration grants for deep geothermal projects in the Haute-Sorne by one-third (see SFOE media releases). With this assistance, the Confederation is supporting additional steps for the Haute Sorne project which will further reduce the risk of a devastating earthquake on the recommendation of the Swiss Seismological Service (SED) at ETH Zurich. Suitable instruments and methods have been successfully tested and their effectiveness demonstrated in the framework of a demonstration project at the Bedretto Laboratory. This progress can be decisive for a pilot project in the Haute-Sorne. “We hope that the breakthrough at Bedretto will strengthen the confidence of the Jura Government and its supervisory authorities in the concept of safety for the Haute-Sorne pilot project and that we will be able to start preparations for exploration well before the end of 2021,” said Peter Meier.
Geo-Energie Suisse remains committed to a step-by-step approach to the pilot project in Haute-Sorne and is confident that the experience gained so far at the Bedretto Laboratory, future findings in Utah and additional support from the SFOE will be provided. projects in the Haute-Sorne at the forefront of safety. With the successful implementation of the pilot project at the Bedretto Laboratory, the hope is that the future of CO production is renewable2-The free and clean electricity from the underground will start in the Jura canton has been given a new boost. According to Peter Meier, “these innovations and outcomes will support the energy and climate policies of Switzerland and the entire growing geothermal industry”.
Overview of important results
- At the Bedretto ETH Zurich Laboratory Geo-Energie Suisse succeeded in creating a permeable geothermal reservoir in the Gotthard mass granite from two boreholes, 350 and 400 meters long, respectively. For this purpose, 10 isolated borehole sections are hydraulically stimulated in successive steps.
- Stimulation-induced microroseism, with magnitudes (Mw) ranging between -3.3 and -1.8 Mw, is about 1 million times smaller than the earthquake that led to the abandonment of the Basel geothermal project in 2006. microseismicity spatial distribution / temporal evolution of microseismicity (2 videos)
- Innovative sensors, measurement and control techniques are tested for the first time and allow observation and control of hydraulic stimulation. These techniques increase safety when creating geothermal reservoirs in crystalline rock. In addition, the seismicity forecasting method developed by ETH Zurich has also been successfully applied in a pilot project. Numbers
- A maximum of 100 cubic meters of water injected per stimulation interval according to a previously prepared risk study. In this way, the radial range of the stimulated fracture system can be limited to keep the seismic low. Despite the low injection volume (about 120 times smaller than in Basel), the permeability of the stimulated interval can be increased by about one to two times on average (a factor of 10 to 100).
- The increased permeability of one of the two boreholes (transmissivity> 1e-4 m2 / s) will be high enough for economic applications in deep geothermal projects. Video.
- The well stimulation area at the Bedretto Laboratory is located at a depth of 1400 meters below the surface. This corresponds to less than one-third of the target reservoir depth at Haute-Sorne (4000 – 5000 meters). The minimum rock pressure at the Bedretto Laboratory is about a quarter of the stress measured at Basel at a depth of 5,000 meters. The natural fracture permeability at Bedretto (before stimulation) is within the range of permeability of the crystalline basement of northeastern Switzerland as measured in the Nagra deep borehole within the framework of the 1980s crystal program.
- The borehole diameter (22 cm) corresponds to the pilot project planned by Geo-Energie Suisse in Haute-Sorne, and approximately one-third of the length of the Haute-Sorne. Experience at the Bedretto Laboratory shows that highly deviated or horizontal boreholes in granite are also technically and economically feasible.
- In March / April 2021, the reservoir will be expanded with a larger injection volume.
- The achievement of this pilot project is the result of national and international innovation cooperation and serves the entire Swiss geothermal industry to increase the safety and probability of future project success.
- DESTRUCTION Demonstration of gentle stimulation treatment of a geothermal reservoir – www.destress-h2020.eu/en/demonstration-sites/bedretto , funded by the State Secretariat for Education, Research and Innovation (SBFI) under contract number 15.0316-1, 691728.
- ZoDrEx Zonal Isolation, Drilling & Exploitation – www.geothermica.eu/projects/zodrex , financed by the Swiss Federal Energy Office (SFOE).
- IASS Innovative Acquisition Systems and Software for Deep Geothermal Evaluation and Monitoring – in collaboration with Utah FORGE www.utahforge.com, financed by the Swiss Federal Energy Office (SFOE).
Source: release via email
Image Notes: Installing a seismometer chain in borehole ST1 to monitor stimulation in borehole ST2, at the Bedretto ETH Zurich Laboratory. The work was carried out under the direction of Geo-Energie Suisse (source / copyright: Geo-Energie Suisse)