Deep-seated geology of the granite intrusions at the Soultz EGS site based on data from 5km-deep boreholes

Gerridina Hooijkaas (1) , Albert Genter (2) , Chrystel Dezayes (2)

1 VU - Vrije Universiteit Amsterdam [Amsterdam]
2 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)

The petrographic model for the deep-seated geology at the Soultz-sous-Forêts Enhanced Geothermal System (EGS) site in the Rhine Graben, France, was revised on the basis of data from 5 km-deep wells. Several types of granite and sub-facies were characterized through thin-section analysis of drill cuttings. Various datalogs were studied to correlate them with petrography. The new geological model of the Soultz site is made up of a massive porphyritic granite that shows some paleo-weathering at its top, overlain by about 1400 m of Mesozoic and Tertiary sediments. Between 2700 and 3200 m depth, the same granite is highly fractured and hydrothermally altered. Below this zone, the granite is less fractured and is very rich in biotite and amphibole. Starting at 4700 m depth is a younger, fine-grained, two-mica and amphibole-rich granite that intrudes into the porphyritic granite.

Mots clés: Enhanced Geothermal System; Granite petrography; Soultz-sous-Forêts; Well logs; Deep-seated geology

Domaines: Sciences de la Terre

Gerridina Hooijkaas, Albert Genter, Chrystel Dezayes. Deep-seated geology of the granite intrusions at the Soultz EGS site based on data from 5km-deep boreholes. Geothermics, 2006, 35 (5-6), pp.484-506. ⟨10.1016/j.geothermics.2006.03.003⟩. ⟨hal-03752100⟩