Geothermal project in Geneva reports successful drilling results and new funding

Lully drilling site, Geneva, Switzerland (source: SIG/ © Magali Girardin 1_0)
Alexander Richter 16 Jul 2020

The geothermal project by SIG near Geneva, Switzerland reports successful drilling results and having received federal funding of EUR 25.3 million for the further development.

In a press communique the geothermal project by the local utility of city of Geneva (SIG), Switzerland announces that the Swiss Federal Office of Energy (SFOE) is providing SIG with a prospecting contribution of CHF 27.5 million (USD 28.3m/ EUR 25.3m) for its exploratory geothermal program. This grant establishes the method of exploring and learning the GEothermie 2020 program, renamed GEothermies (see box). In this context, the exploratory drilling of Lully, which benefits from this subsidy, delivers its first results.

The GEothermies program, piloted by the State of Geneva and implemented by SIG, aims to map the basement of the Geneva basin in order to determine the sites most favourable to the exploitation of geothermal energy, a source of clean, renewable and local energy, and to set up a framework favourable to its development. This program is made up of several modules, including seismic data acquisition campaigns as well as medium depth exploratory drilling which benefit from the subsidies granted.

“The GEothermies program lays the foundations for sustainable and controlled development of geothermal energy in Geneva,” said Antonio Hodgers, State Councilor in charge of the territorial department. “Geothermal energy is a key element in the energy transition. By 2050, geothermal energy could cover 30% of the canton’s heat needs while respecting the environment.”

The Federal Office of Energy awards a grant of CHF 27.5 million for the exploration module of the GEothermies program.

“This OFEN grant is a recognition of the method chosen by the State of Geneva and SIG, a method which consists in knowing the subsoil well before embarking on mining. We want to respect the environment to provide Genevans with this source of renewable energy, available under our feet 24 hours a day,”explains Mr. Christian Brunier, Managing Director of SIG.

Encouraging results for Lully drilling

Part of the subsidy is allocated to the Lully exploratory drilling, located in the town of Bernex. After 8 months of work, this borehole went down to a depth of 1,456 meters, one of the deepest ever dug in Geneva.

Water rises naturally to the surface and its temperature rises to 53 degrees [Celsius] at the bottom of the well. The pressure is high (10 bars), which is very encouraging compared to the presence of water in this sector, however the flows seem limited. Additional tests will be carried out on the Lully borehole in order to know in detail the composition of the subsoil and to assess whether this site can be exploited for geothermal energy.

The objective of this exploratory drilling has been achieved, since it has made it possible to better understand the Geneva subsoil in this specific region by providing essential new geological information which makes it possible to specify the geothermal potential.

The drilling also yielded some geological surprises, such as a great thickness of sand in the form of sandstone, coming from an ancient desert which existed 50 million years ago where Geneva is today!

Lully’s results confirm that water is circulating under our feet but that we must continue the campaigns to acquire seismic data in order to be able to locate the boreholes with more precision, where the flows are high. The Lully drilling, like the previous one in Satigny, is rich in experience and contributes to the skills development of local players. Thus, in the long term, geothermal energy will heat greenhouses, companies or municipalities.

GEothermies: a sustainable and controlled development program

Initiated in 2014, the GEothermies program, plans to carry out 4 exploratory drilling of medium depth in 4 different geological contexts to have a good representativeness of the Geneva subsoil. Two holes have already been drilled in Satigny and Lully. It is estimated that the basement is saturated with water under pressure, but that this water is distributed in a heterogeneous manner. The purpose of these operations is to identify the most favorable geological contexts for the exploitation of geothermal energy.

Geothermal energy will in the future significantly reduce CO2 emissions, thereby reducing dependence on fossil fuels replaced by clean, local energy.

Towards plural geothermal energy for the canton

The knowledge acquired since the launch of the exploratory program in 2014 confirms the potential of geothermal energy in Geneva. The data collected thus made it possible to discover the great geological diversity of the Geneva basin and the significant energy potential of its underground water tables. During the exploratory stages, the perimeter of the program naturally evolved towards the exploitation of groundwater of all depths in order to meet the different needs of the entire territory and the cantonal objectives of energy transition. Today, the potential of geothermal energy as a major agent of the energy transition is established. In this context, the GEothermie2020 program continues to evolve and pursues its ambitions under a new GEothermies signature.

The GEothermies program is currently preparing the exploitation of this energy through a whole range of geothermal solutions: from shallow to medium depth and in the long term, from great depth. Whether it is heating a district, cooling a building or storing energy, the program supports the development of projects to ensure efficient and sustainable use of this local natural resource. Shallow geothermal energy is already the subject of concrete projects that are developing in Geneva (example: the establishment of a district heating network in the Concorde sector in Vernier or the development of groundwater geothermal energy in Versoix ).

To prepare for exploitation and ensure the sustainable implementation of geothermal energy, the State of Geneva continues to rely on SIG, its industrial arm and key partner.

Source: SIG