Multiscale and Multimethod Investigation on Outcropping Analogs: Key Tool for Resources Evaluation and Predrilling Modelling for Geothermal Prospection in Extensional Faults
Lionel BERTRAND, Claire BOSSENNEC, Pauline LE MAIRE, Benjamin DUPONT, Yves GERAUD, Marc DIRAISON
[Université de Lorraine - GeoRessources, France]
The grabens related to the West European Rift system are targets of several drilling projects for geothermal high temperature prospection. Due to the low thermal gradient in comparison to the geothermal fields located in volcanic or active rift areas, the targeted reservoirs are located at great depth, in the fault zones in the metamorphic or magmatic basement rocks. Unfortunately, the reservoir properties and structural knowledge necessary for resources evaluation, predrilling modelling and borehole design are poorly investigated, due to lack of existing boreholes and seismic data with a suitable resolution at great depth. In this context, the DONUTS project, financed by the GIS GĂ©odĂ©nergies aims to develop an integrated method for the geothermal prospection, by combination of Geological and high-resolution geophysical data on outcrop analogs, and large-scale geophysical investigation in the graben (seismic, aeromagnetic, gravimetric et magnetotelluric data). In this study, we show the first tests on outcropping fault zones in the Limagne and the Upper Rhine Graben shoulders. It consists on the development of a new methodology of fractures characterization on 3D data acquired with Lidar or UAV photogrammetric models. On this first step, the comparison between the 3D model and the fracture characterization on the outcrop offers promising results for the development of the method. High resolution geophysical prospection are tested on outcropping fault zone and basement/sedimentary interfaces, with examples on new methodology of aeromagnetic multi-altitude mapping with UAV, resistivity and seismic profiles. They show preliminary results in fault zone detection that will be later enhanced by comparison and modelling of the linked physical properties measured on rock samples. After that, there will be a work on upscaling the fault zones properties and geophysical results in order to constrain the large-scale data.
|        Topic: Geology||Paper Number: 12131|