Description du poste

Rift systems are priority targets for deep geothermal energy (faulted and deep system), however the investment cost associated with deploying this energy is very high and the knowledge on reservoir geometry is often very local, generating failures. Recent studies (Faulds et al, 2006; 2009; Moeck, 2014; Ingebritsen and Gleeson, 2015) show that the geometries of geological formations and especially fault networks have a fundamental impact on the ability to conduct or stop geothermal fluids. Such investigations need to be carried out upstream, and at the scale of the rift system, in order to better understand the reservoirs, what's more when the ambition is to exploit several relatively close sites.
This thesis focuses on the West European Cenozoic Rift System (ECRIS), a potential target for geothermal exploration in France. The area of interest includes the Rhine and Bresse rifts, as well as the Rhine-Saône transfer zone that links these two segments. Several mechanisms of ECRIS opening have been invoked in the literature (extension vs. transtension). Currently published models suggest either a large-scale global transtensional opening in a N-S compressive context (Chorowicz and Deffontaines, 1993; Bourgeois et al., 2007), or a composite dynamic evolving from a NE-SW transtensional context to an E-W to WNW-ESE extension (Rocher et al, 2003), or more classically an E-W to ESE-WNW extension of Oligocene age (Villemin and Bergerat, 1987; Larroque and Laurent, 1988, Bergerat, 1985; 1987; Schumacher, 2002). Work by Briais et al. (2017) has recently revealed a transtensional opening in the Rhine Graben, much earlier than previously expected and of Upper Eocene age. According to the literature, the Rhine Graben was then controlled by N-S compressive constraints, producing local geometries consistent with low extension rates (Bourgeois et al., 2007).