The Soultz-Sous-Forêtssite was the focus of geothermal energy research in France at the beginning of years 2000 and is still one of the major Enhanced Geothermal Systems (EGS) sites in France.

It is drilled through monzogranitic rocks to 5km. A mineralogic and petrophysical description provides a detailed static description of alteration, mainly related to the deposition of illite, which reduce permeability, and high porosity tosudite, rich in lithium (Li).

The exact phasing of alteration is not well understood, and seems to occur in addition to deposition of carbonates. It is key to understand not only the current alteration, but also its evolution with fluid circulation associated to EGS exploitation. Yet, no dynamic alteration study has been performed on the Soultz-sous-Forêt rocks, where commercial extraction of Li is undertaken.

Quantifying fluid-rock interaction will help understanding how alteration can modify the hydraulic properties of the reservoir and how alteration can enrich flowing fluids in Li during EGS exploitation.

Updated on 1er avril 2024