Detection of hydraulic pathways in fractured rock masses and estimation of conductivity by a newly developed TV equipped flowmeter

We developed a flowmeter well logging system that can detect hydraulic pathways in fractured rock mass and applied it to a site where granitic rock is widely distributed. Hydraulic pathways were detected by flow velocity measurement using the Doppler effect of ultrasonic waves, and fractures which acted as hydraulic pathways were specified by a borehole TV camera attached to the system. Fractures with hydraulic conductivity more than 10−7 m/s were detected by the logging system, and the accuracy of the measured conductivities was within one order of magnitude. The newly developed flowmeter system can provide information on the location and conductivity of hydraulic pathways at the borehole for field employment in the earliest stages of site characterization surveys.