Conference paper Open Access

Towards an optimized operation of the EGS Soultz-sous-Forêts power plant (Upper Rhine Graben, France)

Ravier, Guillaume; Seibel, Olivier; Pratiwi, Astu Sam; Mouchot, Justine; Genter, Albert; Ragnarsdóttir, Kolbrún Ragna; Sengelen, Xavier

Increasing heat recovery is challenging for the geothermal projects in the Upper Rhine Graben
(URG). In the framework of the H2020 project MEET, several studies about the thermal effect on the
Soultz-sous-Forêts power plant and its deep wells are being conducted. The main goal is to improve the
thermal power production and optimize the fractured granitic reservoir while minimising environmental
issues. At the Soultz plant, the reinjection at 70°C leads to a well-known scaling formation in the heat
exchanger due to the chemistry of the brine and the thermodynamic changes. Barium, sulphates and metalrich
sulphides precipitate in the surface installation.
Since early 2019, an operating heat exchanger system able to exploit reinjection temperature from 70°C to
40°C is tested in the power plant. This heat exchanger was designed to cool down about 10% of the nominal
mass flow of the Soultz geothermal plant. Dissolved gases and high salinity of the Soultz brine have led to
corrosion issues. The heat exchanger was designed with several tubes alloy in order to determine the best
trade-off between corrosion resistance in Upper Rhine Graben conditions and economical aspect. This alloy
selection will also assess the impact of metallurgy corrosion on scales. In case of successful results with
the prototype, a small scale ORC will be designed and tested at Soultz-sous-Forêts to generate electricity
with full flow and at low temperature.

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