Borehole magnetic susceptibility logging - appt

摘要

Appt. includes air core transmitter and receiver coils plus auxiliary air core nulling coils. A compensated magnetic induction circuit is employed for nulling a major portion of the receiver coil signals, in order that the changes caused by magnetic property change in the surrounding borehole, may be readily detected. The auxiliary nulling coils are pancake shaped and are located outside the fields of the transmitter and receiver coils. But they are located on the logging tool so that they are subject to the same ambient conditions as are the transmitter and receiver coils.