Naturally fractured granites as promising targets for HT geothermal exploration: Impact of fault network geometry
Résumé
To meet the challenge of energy transition, geothermal exploration must identify new geological targets. In fact, the current areas of operation remain very specific (volcanic context or active extension zones), which limits the French potential. By focusing exploration on the search for drains (faults), many more areas of interest can be explored. Crustal fault zones hold great promise as potential geothermal reservoirs, but they remain largely untapped and unexplored. The Margeride Granitic Complex, located in the south of the French Massif Central, is a pluton with intense reactivated fractures. Here, two distinct fracture zones with particular geometric features are studied: First, the intersection of two fault zones, N140E and N030E, near the village of Chaudes-Aigues (known for the emergence of thirty springs, including the Par spring at 82°C) and, second, the Margeride fault zone, which varies in thickness from 100 m to 2,500 m in the North (Saint-Flour). The aim of this study is to highlight the geothermal potential of the fractured basement using field characterisation, fault density analysis and 3D numerical modelling. Our results show that, at shallow depths, thermal anomalies are preferentially located around the thickest parts of fault zones and at the intersection of fault networks
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