The Swiss Federal Office of Energy (SFOE) has granted $28.3 million to SIG, the local utility of Geneva, for its exploratory geothermal program. This grant sets forth the method of exploration for the program GEothermie 2020, renamed GEothermies.
Drilling site courtesy of SIG
The GEothermies program, piloted by the State of Geneva and implemented by SIG, aims to map the subsoil of the Geneva basin in order to determine the most favorable sites for the exploitation of geothermal energy, a source of clean, renewable and local energy, and to set up a framework favorable to its development. This program is made up of several stages, including seismic data acquisition and drilling medium depth explorations which benefit from the subsidies granted.
"The GEothermies program lays the foundations for sustainable and controlled development of geothermal energy in Geneva,” explains Antonio Hodgers, state councilor in charge of 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. "
"This … grant is recognition of the method chosen by the State of Geneva and SIG, a method which consists [of] knowing the subsoil well before embarking on mining. We would like to respect the environment to provide Genevans with this renewable, available source of energy under our feet 24 hours a day,” explains Christian Brunier, CEO of SIG.
Part of the subsidy is allocated to the Lully exploratory drilling, located in the town of Bernex. After eight months of work, this borehole went down to a depth of 1,456 meters, one of the deepest ever dug in Geneva.
Tests will be carried out on the Lully drilling in order to know in detail the composition of the subsoil and assess if this site can be exploited for geothermal energy.
The objective of this exploratory drilling was achieved, since it made it possible to better understand the Geneva subsoil in this specific region by providing new geological information essential to understanding the geothermal potential.
The drilling also delivered some geological surprises, such as a thick layer 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 the ground but seismic data needs to be acquired in order to be able to locate the boreholes with more precision, where flow rates are high.
Initiated in 2014, the GEothermies program, plans to carry out four exploratory boreholes of medium depth in four different geological areas to have a good representation of the Geneva subsoil. Two holes have already been drilled in Satigny and Lully. It is estimated that the subsoil is saturated with water under pressure, but that this water is distributed heterogeneously. The purpose of these operations is to identify the most favorable geological areas 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.