Crustal Fault Zone: New geothermal reservoir? Structural dataset and preliminary 3D TH(M) modelling of the Pontgibaud fault zone (French Massif Central)

Hugo Duwiquet (1, 2, 3) , Laurent Guillou-Frottier (1, 2) , Laurent Arbaret (1, 2) , Theophile Guillon (4) , Mathieu Bellanger (3) , Michael Heap (5)

1 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
2 Géodynamique - UMR7327
3 TLS-Geothermics
4 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
5 IPGS - Institut de physique du globe de Strasbourg

Numerous recent studies indicate that crustal-scale fault zones represent efficient conduits for meteoric fluids to flow down to mid-crustal depths (Haines et al., 2016). The present study aims to understand the potential of a new and novel type of geothermal system for high temperature and electricity production: Crustal Fault Zones (CFZ). One such example is the Pontgibaud fault zone (French Massif Central), a 30 km-long and 3 km-wide mineralized fault zone. The Pontgibaud fault zone is also characterized by numerous CO2-rich-thermo-mineral springs. Moreover, this area is also defined by local and regional surface heat flow values of 110 mW/m 2 (International Heat Flow Commission database) involving temperature gradients between 37 and 41 °C/km. The Pontgibaud fault zone has been well studied in the last few years (Bellanger et al., 2017), electrical conductivity anomalies have been identified (Ars et al., 2019) and the temperature anomaly has been estimated (Duwiquet et al., 2019). Estimation of the geothermal resource have been established by 2D geological numerical modelling, with Thermal-Hydraulic (TH) coupling. Here we propose to integrate structural field observation into 3D geological numerical modelling with Thermal-Hydraulic-(Mechanical) (TH(M)) coupling. We then evaluate the various applications for high-temperature geothermal exploitation.

Mots clés: Crustal Fault Zone; high-temperature geothermal system; structural geology; 2D and 3D numerical modelling; TH; THM; French Massif Central

Domaines: Tectonique; Géologie appliquée

Hugo Duwiquet, Laurent Guillou-Frottier, Laurent Arbaret, Theophile Guillon, Mathieu Bellanger, et al.. Crustal Fault Zone: New geothermal reservoir? Structural dataset and preliminary 3D TH(M) modelling of the Pontgibaud fault zone (French Massif Central). 45th Workshop on Geothermal Reservoir Engineering, Feb 2020, Stanford, CA, United States. ⟨insu-02481052⟩