Technischer Bericht NTB 85-50

Sondierbohrungen Weiach, Riniken, Schafisheim, Kaisten, LeuggernGeophysikalische Daten

Up to the 25th of May 1985, six deep boreholes have been drilled and investigated in Northern Switzerland as part of Nagra's geological exploration program. The "in situ" investigations included comprehensive geophysical logging programs. They were carried out to provide data for the petrophysical and geological characterisation of the drilled rock formations, the location and orientation of planar discontinuities such as fractures or dykes, and finally to acquire geophysical and technical reference data. All relevant results will be published in due course as part of multidisciplinary investigation reports on the individual boreholes. The first of these reports on the BOETTSTEIN borehole is now available (NTB 85-01); the data from the five remaining boreholes are presently being processed.

It seemed desirable to give all the working teams and project groups involved in the evaluation of the drilling results early access to the geophysical data set. With the present report it is intended to provide a clearly arranged and compact summary of the most important raw data originating from the boreholes WEIACH, RINIKEN, SCHAFISHEIM, KAISTEN and LEUGGERN. In addition to results, the report contains a brief description of the various tools and investigation methods which were used, as well as comments on field operations and data quality. This preliminary report does not however contain any interpretation or discussion of the recorded data set.

Apart from the introductory chapter the report is structured with respect to boreholes. Chapters and enclosures which relate to a specific borehole always carry the same main number (e.g. 4.x for WEIACH). The second digit either refers to a standardized subchapter or the type of enclosure. The following data are presented as enclosures for each borehole:

Enclosure x.1:

Overview of all geophysical surveys carried out in the borehole.

Enclosure x.2:

Composite-Log. Compilation of the most important logs (scale 1:1000) together with the geological record. Consecutive depth sections (each ca. 1000 m) are designated a, b and c.

Enclosure x.3:

Electrical resistivity or ultrasonic reflection image of the borehole wall. One or more small sections (scale 1:10) are presented as data samples.

Enclosure x.4:

Seismic time/depth function (T/Z curve, vertical scale 1:5000) on the basis of sonic, check-shot and VSP data.

Enclosure x.5:

Seismic velocity/depth functions (vertical scale 1:5000) on the basis of sonic and check-shot data.

Enclosure x.6:

Synthetic seismograms and vertical seismic profile (VSP). Vertical scale: 1 cm = 0.1 s

Enclosure x.7:

Borehole trajectory. Graphic and tabular presentation (depth conversion table).

Enclosure x.8:

Density and density difference profiles on the basis of borehole gravity and LDT data (vertical scale 1:5000; WEIACH borehole only).

These enclosures were designed to give a general overview of the available data and their information content. They are not always suitable as a direct basis for further interpretation or detailed studies.