| Abstract |
The tectonic and sedimentological evolution of the Rhine Graben has favored geothermal exploitation, particularly in northeastern France. Exploration focuses on the granitic basement and its unconformable interface with the Lower Triassic Buntsandstein Group, characterized by complex structural and mineralogical heterogeneities. Clay minerals play a critical role in tracking hydrothermal fluid circulation. Hydrothermal clays in the granitic basement, primarily illite and illite-rich illite/smectite mixed-layers (± chlorite) have been well-characterized. Differentiating diagenetic from hydrothermal clays within sedimentary sequences, is essential for their use as key markers in hydrothermal fluid circulation pathways. Given the complexity of fault and fracture networks, and sedimentological facies variations, characterization must be integrated with a sedimentological and structural approach. In addition to determining the origin of clay minerals, clay textural properties directly impact reservoir quality by controlling porosity and permeability, and the evolution of reservoir properties during exploration, as they influence fluid dynamic. A calibration methodology is developed by combining field-based semi-quantitative Short-Wave InfraRed spectroscopy (SWIR) data with accurate laboratory analyses: X-Ray Diffraction (XRD), Rietveld refinement, and Scanning Electron Microscopy (SEM). This integrated approach enhances clay identification, improves spatial distribution analysis, and strengthens the detection of permeable zones in fractured geothermal reservoirs.The dataset comprises over 1250 m of core and cuttings from three wells (EPS-1, GRT-1, GRT-2) at Soultz-sous-Fôrets and Rittershoffen. By calibrating SWIR with XRD and SEM-based mineralogical, and textural analyses, this study provides a framework for accurately mapping clay networks, improving reservoir quality assessment, and optimizing fast and cost-effective exploration strategies in complex, fractured geothermal systems. |