Field Evaluation Of A New Borehole Resistivity Probe Using Capacitive Electrodes.

A prototype resistivity probe using capacitive electrodes has been built under a collaborative<br>project funded jointly by the Geological Survey of Canada (GSC) and IFG Corporation, a<br>Canadian manufacturer of borehole geophysical instrumentation. The GSC carried out field tests<br>at its borehole test facilities in Ottawa and at the New Calumet massive sulphide deposit in<br>Quebec. Results indicate that the capacitive technique is sensitive in the resistivity range 100-<br>10,000 ohm-m and compares well with galvanically and inductively measured resistivities. Field<br>tests were also carried out for several transmitter-receiver spacings and in plastic-cased fluidfilled<br>boreholes. Capacitive resistivity logs acquired in a plastic-cased borehole are almost<br>identical to those acquired in the same but uncased borehole. Therefore, capacitive resistivity<br>logs promise to be valuable for use in environmental applications where boreholes drilled in<br>unconsolidated sediments are often plastic-cased.