New study highlights high-potential geothermal areas in St. Gallen, Switzerland

A new study commissioned by the Canton of St. Gallen in Switzerland examines the potential for geothermal heating in the Canton, identifies areas with high potential, and proposes a phased exploration and development plan.

The full report, “Potential of Medium-Depth and Deep Geothermal Energy in the Canton of St. Gallen” (Potenzial der mitteltiefen und tiefen Geothermie im Kanton St. Gallen) can be downloaded from the Canton’s official website.

The first venture of St. Gallen into geothermal unfortunately did not yield good results. The geothermal well was drilled in 2013 to a target depth of 4002 meters. During the testing phase, a gas kick was detected, prompting the injection of drilling mud into the well. Following the injection activity, a seismic event of 3.5 magnitude on the Richter scale was detected, which was widely felt and caused some structural damage. Even after the well had been controlled, there was found to be insufficient water in the well to further the project, resulting in its abandonment in 2014.

About thirteen years after the incident, the Canton is once again seeking to evaluate how geothermal resources can be harnessed in St. Gallen. As pointed out by the study, the previous 3D seismic surveys and the old deep geothermal well provides some insights on the deeper subsurface layers in the Canton, but a wide investigation is still needed to better understand the rest of the region.

The study indicates that there are several subsurface layers in St. Gallen that could be interesting for geothermal utilization. The gravel deposits in glacial channels (200-600 meters) can be explored with relatively little investment and low risk. These may host waters at 20-30 ºC, making them interesting for seasonal heat storage.

At greater depths (1000 to 2000 meters), water-bearing fractures and fault zones may host thermal waters at slightly higher temperatures, about 40 to 70 ºC. Waters from these depths can be extracted and enhanced with heat pumps, allowing their use in individual or large-scale heating systems. This is similar to the geothermal heating scheme in place in Riehen.

Finally, very deep geothermal resources (over 3000 meters) may have potential for both electricity generation and district heating supply. This has huge potential, but also needs more intensive investigations and carries more risk.

Possible drilling locations proposed by the study include Buchs, Benken, Ebnat-Kappel, Wildhause, Walenstadt, Sargans/Mels, and Widnau/Diepoldsau. However, the study also acknowledges that there is still a significant level of concern from the population of the risk of earthquakes resulting in any geothermal activity. For this reason, communication has to be done early and in a transparent manner. There also needs to be risk analysis and mitigation measures in place.

Source: Swissinfo.ch and Canton of St. Gallen