Switzerland aims to reach net-zero CO2 emissions by 2050 (BAFU, 2021). Getting there through geological CO2 storage and geothermal heat mining depends on properly understanding reservoir properties — the structural and permeability architecture of target reservoirs is essential input for the numerical models used to assess storage and production potential, minimise fluid injection and extraction uncertainties, and reduce exploration risk. The Muschelkalk aquifer (Triassic), including the Schinznach Formation, is one of Switzerland’s key potential aquifers for gas storage and hydrothermal geothermal systems (Chevalier et al., 2010). Its matrix permeability is relatively well known (Diamond et al., 2019); the magnitude and distribution of its fracture permeability, and the structural controls behind it, are not.
FReMUK, Wutach-based: this project characterises multiscale fracture networks within the Muschelkalk — assessing the style and intensity of natural fracture networks at sub-seismic scale and explaining their regional variability. It integrates detailed field observations from outcrop analogues in the Wutach Gorge of southern Germany (cliff exposures along 5–12 km-long E–W and N–S transects within the Tabular Jura, aligning with and crossing fault strands of the Freiburg–Bonndorf–Bodensee Fault zone), building a multiscale structural framework and discrete fracture network models — crucial for upscaling fracture properties to estimate effective regional permeability across the Swiss Molasse Basin. This outcrop-based framework will draw direct comparison with the Schlattingen horizontal borehole study — Switzerland’s only borehole with directly measurable subsurface fracture data.
The Schlattingen study: this project focuses solely on borehole data from Switzerland’s only horizontal borehole, at Schlattingen — the only place fracture data can be gathered directly from the subsurface reservoir target itself, rather than inferred from analogues. From this borehole data, it builds conceptual models of fracture networks and structures informed by regional tectonics. Comparing the two builds a genuinely multiscale understanding of the reservoir’s permeability architecture, and informs exploration and development of the subsurface more broadly.