Perform Test of a Directional Borehole Rader

Nagata, Kazuhiro*; Kajikawa, Kazahiro*; Mizuochi, Yukihiro*

Directional borehole rader (DBRD) measurements and core description were carried out and the reliability of fracture orientations determined by DBRD was discussed. DBRD ran into the borehole (01MS-06, depth 400m) drilled at the Syobasama site and 17 fractures were detected. 10 fracture orientations were determined from those fractures. Reflection waves from amother borehole (MIU-2) located about 14m away from 01MS-06 borehole were not detected, so the reliability of orientation could not be evaluated quantitatively. Judging from the result of a laboratory experiment, wa conclude that the error of fracture orientations determined by DBRD, in case of clearly observed reflector planes, would be within the range of plusmn 10 deg. in this work. Comparing DBRD reflector plane with fractures obtained by the core logging, it is found that the reflection occurs from fractured zone of rock mass. DBRD measurements with directional antennas having sufficient resolution are applicable to ...