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Geothermal potential of underground aquifers in Geneva State

The Industrial Services of Geneva (SIG) mandated Dropstone to carry out a feasibility study of the Rhône River aquifer in the municipalities of Lancy, Onex and St-Jean. In order to evaluate the geothermal potential of the aquifer, our team of hydrogeologists investigated data from previously drilled boreholes, produced a 2D model of the water table and analysed its geological and hydrogeological characteristics. This study was performed from August 2016 to December 2017.

Another study for the SIG in the wider area of Geneva is currently ongoing since May 2019. Dropstone investigates the geothermal potential of a shallow and transborder aquifer that originates from France (Haute-Savoie) and extends in Switzerland, below the municipalities of Puplinge, Chêne-Bourg, and Thônex in the canton of Geneva. Dropstone is working with data publicly available from the Geological Survey Database and use them to represent the precise geometry of the aquifer. Dynamic maps displaying the underground water flow are produced. The information from the DB is verified at field level with hydrogeological tests (pumping tests and water quality analysis) that are regularly performed.

Dropstone has drilled four exploratory boreholes in 2021 in the Puplinge aquifers, in order to specify accurately the geological features of the undeground, from the surface down to the Tertiary Molasse. The drillings have allowed to evaluate the low-enthalpy geothermal resources of the aquifer, and the possible interconnections between aquifers. This work has also allowed to clarify the local geology and hydrogeology, which until now were largely unknown beyond the surface water table. The first drilling, entirely cored, reached the underlying tertiary rocks at a depth of 103 m. It brings precious punctual information and allows to complete the hydrogeological characteristics of the Puplinge aquifer.

The short movie below illustrates the different steps of the project, from the installation of the site machinery to the drilling, the core sampling and the pumping tests. Dropstone is very pleased to actively contribute to the priority of Geneva’s energy policy and to the development of geothermal energy as a clean, local and renewable energy source.

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