Institute of Geological Sciences

CO2 Sequestration

Muschelkalk Aquifer for Gas Storage and Geothermal Energy

Our literature study (Chevalier et al., 2010) identified several major saline aquifers within the sedimentary rocks of the Swiss Molasse Basin. We are now investigating in detail the gas-storage and geothermal properties of the largest of these, the "Upper Muschelkalk" carbonate aquifer.

Upper Muschelkalk
Extent of the Upper Muschelkalk below 800 m depth in the Swiss Molasse Basin. The unit is ~65 m thick, it dips monotonically 4° SE and is sealed by Keuper evaporites. Coloured area in 800–2500 m depth interval shows theoretical potential for CO2 sequestration (Chevalier et al., 2010). Grey area shows unit at >2500 m depth. Only the area south of the 120 °C isotherm has potential for electricity generation.

We are studying rock cores, geophysical logs and hydraulic tests from deep boreholes. The samples and borehole data have been kindly provided by Nagra and the Swiss Petroleum Company Ltd. SEAG. Our aim is to define the 3D distribution of connected porosity and permeability throughout the aquifer. Borehole coverage is insufficient to reliably interpolate empirical measurements throughout the aquifer, hence basic conceptual understanding of the geological evolution of the aquifer is required to enable predictions into areas without borehole information.

Upper Muschelkalk
Sample of porous Upper Muschelkalk from the Weiach well (846 m)

The distribution of porosity and permeabiilty depends on (1) processes that occurred during and shortly after deposition of the U. Muschelkalk carbonate sediments in the Middle Triassic, and on (2) events of mineral dissolution (porosity enhancement), mineral precipitation (pore clogging) and fracturing that occurred later upon deep burial and uplift of the unit during the Alpine orogeny. Accordingly, two PhD projects, supported by four MSc projects, are directed at elucidating these key processes.