A successful geothermal exploration campaign on the Coast

The subsoil contains many resources, one of which is particularly attractive for our energy system while being kind to the climate: geothermal energy.

In order to image the subsoil, to better understand it and to evaluate its geothermal potential, it is often necessary in Switzerland to carry out a prospecting campaign. Such a campaign generally consists in using non-invasive surface geophysical methods to collect data on the subsoil which will allow, after analysis and interpretation, to identify one or several geological environments favourable to the exploitation of the heat contained in the deep subsoil. Only an exploratory drilling will allow to confirm - or to deny, because nothing is ever guaranteed in the subsoil - the presence of such a resource and, if necessary, to characterize it in order to use it for the production of electricity and/or heat.

Three prospecting campaigns to identify geothermal resources have been carried out in Switzerland over the last twelve months, more precisely in the cantons of Vaud, Geneva and Basel-City. The Vaud prospecting campaign carried out last summer by EnergeÔ SA has just delivered its first results: the news are good for the heat supply of the La Côte region.

Good geothermal prospects for La Côte

In August 2021, vibrating trucks collected data over an area of about 414 km2, crossing at night about thirty communes in the southwestern part of the Morges district. Two lines were drawn: one of 11 km from Saubraz to Montricher and a second one of 27 km, starting from the Aubonne/Etoy area and ending in the Nyon area. The analysis of these seismic data showed the high geothermal potential of this part of the Vaud territory.

However, this geothermal resource should only be exploited if there is a need for heat on the surface. After an initial analysis of the needs of the municipalities in the surveyed area, about ten opportunities to develop geothermal energy were identified. The depth of these potential projects varies from 100 m to 2,300 m, targeting geothermal waters from 25°C to 90°C. Each of these projects has its own technical requirements and a unique schedule.

One of the most promising projects is located in Nyon where a strong match between geothermal resources and the city's heating needs has been identified. The conditions are indeed favourable to supply the future district heating network of Nyon. In fact, the Dogger aquifer (geological layer) located at a depth of 2,300 m has been sufficiently characterized to consider drilling directly. On the surface, in addition to the valorization of geothermal heat, two plots of land have already been identified as being suitable to receive, initially, a drilling platform, then, eventually, a thermal power plant. The detailed planning of this project is underway.

To know if La Côte will soon become as famous for its geothermal projects as for its wines, we will have to drill. EnergeÔ SA's first drilling will take place in the village of Vinzel in early autumn and could confirm the productivity of one of the geological environments located at a depth of 2'300 m and identified as promising in the La Côte region.

Nicole Lupi, specialist in deep geothermal energy at the SFOE

Image: www.energeo.ch