Hydraulic test for evaluation of hydrophone VSP
Yabuuchi, Satoshi; Koide, Kaoru
This hydlraulic test was carried out at the test site of Tono Geoscience Center, Mizunami-shi, Gifu Pref. in order to evaluate the reliability of the hydraulic conductivity estimated from hydrophone VSP experiment. From March to April 1997, we carried out measurements of pore-water pressure at five depths and permeability tests at seven depths down to G.L. -300m, within a borehole drilled in granitic rock. We compared the results of hydraulic test with hydrophone VSP experiment on condition that a single open fracture existed, and we obtained two notable results. First, for the granitic rock at which a single open fracture was found by BTV and also detected by hydrophone VSP experiment, the hydraulic conductivity was 1.5410 cm/sec, while for the same granitic rock at which another single open fracture was found by BTV but not detected by hydrophone VSP experiment, the hydraulic conductivity was less than 610 cm/sec. Second, we converted the hydraulic conductivity of 1.5410 cm/sec which was obtained in a hydraulic test section of length 2.5m into an equivalent value for a single open fracture of width 1 mm. The converted value (3.810 cm/sec) was similar to the hydraulic conductivity estimated from hydrophone VSP experiment. In conclusion, the hydraulic test results shows that hydrophone VSP is useful to estimate an approximate hydraulic conductivity of a single open fracture.