| Title | Toward a Better Understanding of the Fluid Circulation in the Rhine Graben for a Better Geothermal Exploration of the Deep Basins |
|---|---|
| Authors | Chrystel DEZAYES, Catherine LEROUGE, Bernard SANJUAN, Claire RAMBOZ, Michel BRACH |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | Rhine Graben, fractures, faults, fluids, mineralogy, tectonic, geochemistry |
| Abstract | In the Upper Rhine Graben, geothermal projects are strongly under development, particularly for the exploitation of fluid in the deeper part of the basin. This type of reservoirs constitutes a fractured dominated system. However, the hydraulic behaviour of the fracture network is poorly known, such as connexion, main fluid flow direction, role of the fault zone versus minor fractures, the deformation types (cataclase, fault, crack…) but its knowledge constitutes an important way to better target the exploration works. Combining data from structural analysis, mineralogical analysis of fracture filling from outcrops and drilling cores and fluid geochemical analysis from deep boreholes, we propose a new model of fluid circulation in the deeper part of the Upper Rhine Graben in order to explain the location of the thermal anomalies. We propose two approaches for that. The first approach is to study the fillings of the fracture which plug partially or totally the current fluid flow. The second approach is to determine the nature of the palæo-circulations by studying fracture fillings, their textures and establish mineral sequence of fillings in relation to the tectonic phases and the geological history of the basement. And finally we compare chemistry of palæo-fluids with those of present-day fluids which flow in the deeper part of the Upper Rhine Graben. A new conceptual model of the fluid circulation in the deeper part of the Rhine Graben is proposed in order to 1) give basis for physic models and 2) precise the best location for detailed geothermal exploration. |