Technical Report NTB 89-09

Interpretation of hydraulic testing at the Schafisheim borehole

This report presents the results of hydrogeologic interpretations of the analyzable single packer, double packer, and H-log tests conducted in the Schafisheim borehole. A brief discussion of the testing and interpretation methods is also presented. Data analysis was performed using the INTERA Graph Theoretic Field Model (GTFM) which permits borehole pressure history and thermally-induced pressure effects to be incorporated into the simulations.

Formation pressures (and corresponding equivalent freshwater heads) were determined for 11 of the test intervals. The calculated equivalent freshwater heads were at 370 m a.s.l. (Malm) and 444 m a.s.l. (Muschelkalk) for the sedimentary units, and were in a tight range from 366 m a.s.l. to 370 m a.s.l. in the crystalline portion of the borehole.

Hydraulic conductivities were estimated for 37 different hydraulic tests in the Schafisheim borehole. A detailed analysis was performed for 16 intervals, and a less in-depth review was conducted of an additional 21 low permeability intervals (interval 1972.6 was tested twice). Interpreted hydraulic conductivities ranged from 5.0E-06 ms­-1 to less than 1.0E-12 ms-1. Zones of high hydraulic conductivity (greater than 1.0E-09 ms-1) were observed at the following approximate true vertical depths: 552.9 m to 563.0 m, 1,227.6 m to 1,286.9 m, 1,564.1 m to 1,607.6 m, 1,882.8 m to 1,903.3 m, and 1,953.7 m to 2,005.8 m.

A base case specific storage of 1.0E-07 m-1 was generally used for the crystalline rock. A sensitivity analysis was conducted for some tests to determine the uncertainty in the best estimate of K related to the choice of specific storage. In these cases, specific storage was varied by 1 to 2 orders of magnitude from the base case value.