The Rheinau borehole provided further insights into the safety of a deep geological repository in Northern Switzerland. Nagra carried out measurements to establish the significance of the existing fault in the Opalinus Clay, particularly with regard to the safety-relevant properties of the rock.
Angled borehole
Data for this region were already available from a deep borehole previously drilled in the community of Benken. As part of the investigations carried out during Stage 3, deep boreholes were also drilled in Marthalen and Trüllikon.
Based on earlier 3D seismic investigations, Nagra suspected the presence of so-called “steeply dipping faults” deep underground at the edge of the Zürich Nordost siting region east of Rheinau. “Steeply dipping” means that the faults have a vertical trend. For this reason, the decision was made to drill the Rheinau borehole not vertically, but at an incline.
The faults were thus intentionally penetrated for investigation purposes. This was an important decision, as the results can also be transferred to the other siting regions. The key finding is that the Opalinus Clay is tight even in the fault area. The self-sealing capacity of the Opalinus Clay was also confirmed.
Find out more about the Benken exploratory borehole in Technical Report NTB 00-01.
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Further deep boreholes
Trüllikon-1 borehole
The Trüllikon borehole was the first deep borehole to be drilled in the Zürich Nordost siting region as part of Stage 3 of the site selection process.
Marthalen borehole
The Marthalen borehole was the second deep borehole to be drilled in the Zürich Nordost siting region as part of Stage 3 of the site selection process.
Bülach borehole
Bülach was the first deep borehole to be drilled in the Nördlich Lägern siting region as part of Stage 3 of the site selection process for a deep geological repository.
Stadel-3 borehole
Stadel-3 was the second deep borehole to be drilled in the Nördlich Lägern siting region as part of Stage 3 of the site selection process.
Stadel-2 borehole
The Stadel-2 borehole was the third deep borehole to be drilled in the Nördlich Lägern siting region as part of Stage 3 of the site selection process.
Bachs-1 borehole
The Bachs borehole was the fourth deep borehole to be drilled in the Nördlich Lägern siting region as part of Stage 3 of the site selection process.
Bözberg-1 borehole
Bözberg-1 was the first deep borehole to be drilled in the Jura Ost siting region as part of Stage 3 of the site selection process.
Bözberg-2 borehole
Bözberg-2 was the second deep borehole to be drilled in the Jura Ost siting region as part of Stage 3 of the site selection process.
Work report
