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Communication Dans Un Congrès Année : 2023

Scale and spatial variations in the geothermal fractured system of Upper Rhine Graben

Résumé

The Upper Rhine Graben, on the France-Germany border, is known for its thermal anomaly and several industrial geothermal deep exploitations are present. These exploit the deep hot fluid circulating through fracture network in deeper part of the graben, below 1000m, in Triassic sandstones and Paleozoic granite. Knowledge of this fracture network is then crucial to better targeted the fluid and developed geothermal energy in the French energy mix. For that, we analyzed fracture network in outcrops of the graben shoulders, in Vosges and Black Forest massifs, and inside the graben from deep Soultz-sous-Forêts wells, first Enhanced Geothermal System (EGS) in the world. This analysis consists in orientation and distribution measurements along 1D sampling, like scan lines on outcrops or along boreholes. At Soultz-sous-Forêts, one of the wells was fully cored and fractures on thin sections have been observed in the quartz grains, in addition to fractures on cores. Results show various fracture sets present in Paleozoic basement and above Triassic sandstones that can be linked to tectonic history of the region: submeridian fracture set is linked to graben opening at Tertiary and the other sets, NE-SW, NW-SE and E-W, originated from Hercynian orogeny and reactivated in Tertiary. These fracture sets are present at various scale from the whole Rhine Graben to the quartz grains in the granite basement. However, while E-W fracture set is present in all studied sites, its proportion varies widely from a place to another. In central part of the graben, E-W fractures constitute the major set. This could be linked to Lalay-Lubine-Baden-Baden fault zone and the creation of the E-W Permian local sedimentary basin at this place. This study highlights importance of the Hercynian tectonic heritage in the fracture network of Upper Rhine Graben, which constitutes the basis of the fluid circulation and the understanding of the geothermal system.

Domaines

Tectonique
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Dates et versions

hal-04184819 , version 1 (22-08-2023)

Identifiants

  • HAL Id : hal-04184819 , version 1

Citer

Chrystel Dezayes. Scale and spatial variations in the geothermal fractured system of Upper Rhine Graben. AGU Fall Meeting 2023, Dec 2023, San Francisco, United States. ⟨hal-04184819⟩

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