Technical Report NTB 89-10

Final interpretation of hydraulic testing at the Siblingen borehole

This report contains the results of the interpretation of hydraulic testing in the sedimentary and crystalline rocks of the Siblingen borehole. Hydraulic tests were performed between September 1988 and April 1989 in single packer, double packer and open hole configurations. A total number of thirty one separate intervals covering about 90 % of the Siblingen borehole length were tested. Preliminary field analyses documented in "Quick-Look" Reports were performed for all intervals tested. Detailed interpretations were conducted for 16 selected intervals and documented in stand-alone reports. The results of both types of analysis are included in this final report. Data analysis was performed using the ITA Transient Interactive Analysis System (TRIAS) and the INTERPRET analysis code of Scientific Software-Intercomp. Representative test interval parameters including hydraulic conductivity test interval static pressure and equivalent freshwater hydraulic head are interpreted and recommended. Since no reliable in-situ estimation of the specific storage value was possible it was calculated directly from the input parameters. For the crystalline rock a value of 8.6E-08 m-1 was generally used. Interpreted hydraulic conductivities range from 1.5E-06 ms-1 to 2.0E-04 ms-1 for the sedimentary aquifers and from 5.1E-11 ms-1 to 4.0E-04 ms-1 for the crystalline rock. Formation pressures and corresponding hydraulic heads were estimated for 26 of the 31 test intervals. The determined equivalent freshwater heads range from 462 m asl for the Muschelkalk aquifer on top to 436 m asl for the lowest part of crystalline rock. Relatively high hydraulic conductivities encountered in the Siblingen borehole are expected to minimize the influence of the pretest borehole pressure history on the test data. Therefore, pressure history was generally not included in the analysis.

This report also contains a brief description of the testing equipment and performance as well as testing and analysis methods used for the determination of hydrogeologic parameters.