The H2020 Multidisciplinary and multi-context demonstration of EGS exploration and Exploitation Techniques and potentials (MEET) is a European project, which aims at enhancing demonstration of geothermal energy production throughout Europe.
Part of the MEET project is dedicated to characterization of geothermal reservoirs analogues in order to better understand the behavior of target exploited reservoir, especially the role of the fracture network in the fluid flow path. ULS concentrates its study on an analogue to the Soultz-sous-Forêts (SsF) granitic reservoir which is located in the southern part of the Death Valley (DV), the Noble Hills range (NH, CA, USA). The analogy approach allows us to gather knowledge of fracture systems in various geological settings considering the influence of strain acting on fault zones. Our investigations contribute at a better targeting of economically sustainable production zones to be drilled.
In July 2020, the ULS team performed one-week fieldwork in the southern part of the shoulders of the Upper Rhine Graben (URG). The goal was to characterize deformation present in the URG and to compare it with the one found at NH. This work was concentrated on profiles found in underground mines within the Vosges Mountains (Sainte-Marie-aux-Mines) and the Black Forest (Schauinsland).
In both mine galleries, impressive fracture systems were observed. Photogrammetrical data were acquired to build a 3D model of the chosen outcrops. Qualitative and quantitative analyses of fractures have also been acquired on specific fault zones. The obtained data are to be compared with the one obtained at NH.
Figure 1: 3D model based on photogrammetrical data of a gallery from the Schauinsland mine (Black Forest, Germany).
The DV and URG sites present high strain zones rich in clay minerals. All together it appears that similar features are found in all analogue investigated. This imply on one hand that DV is to be considered as a good analogue of the SsF site and on the other hand, that deformation amounts on fault zones from the URG were probably underestimated.
Figure 2: Two fault gouges examples respectively from A) Death Valley (USA) and B) Schauinsland mine (Black Forest, URG, Germany). Note similarity between both structures indicating each case high strain concentrating.
The ASEPAM and the Forschergruppe Steiber associations are greatly acknowledged.