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Abstract:
The Upper Rhine Graben is defined as brown site in the IMAGE project, as it is an established geothermal area, where a solid experience with standard exploration tools and a database exists. A 3D local geological model has been built on the area. Located between Strasbourg and northern Sélestat, it covers a 35 km x 45 km horizontal zone with a 7 km vertical extension. Based on a detailed geological study combining data derived from 15 previous oil boreholes and more than 200km length of seismic profiles, the main sedimentary interfaces including geological layers and faults have been interpreted between the outcropping Quaternary layers and the deeper parts made of Permo-Triassic formations (Dezayes et al., 2010). Therefore, seven formations have been modelled. They are limited by the following six geological interfaces:
- Base of the Oligo-Miocene (Top of the Pechelbronn Formation)
- Base of the Tertiary sediments
- Base of the Upper Jurassic (Top of the Aalenian)
- Base of the Upper Triassic (Base of the Keuper)
- Base of the Muschelkalk
- Base of the Buntsandstein
The selected seismic lines have been reprocessed and interpreted in order to determine the geometry of the main interfaces of the geological formations. After converting the time of the seismic interpretation into depth, the location of these interfaces has been imported in the GeoModeller software developed by BRGM. Faults have been identified on each seismic profile. Then a coherent 3D correlation has been done between all profiles. After building a consistent fault pattern, the formation interfaces have been interpolated using the potential field cokriging method and geological rules (Lajaunie et al., 1997; Calcagno et al., 2008). In this method, interface locations, orientation data, fault influence, and geological history have been taking simultaneously into account.
Associate to this geological model, the conductive results of a larger thermal model (Freymark et al., 2016) and the bottom hole temperature interpolation (Carré, 2011) have been set in the same 3D space.
