Deep investigation induction logging with mirror image coil arrays

摘要

A sonde for induction logging of boreholes comprises a zero mutual inductance transmitter-receiver coil array comprising at least two coil groups that are time or frequency multiplexed. Each group comprises a coil array which is asymmetric and the coil array of one group are the mirror image of the coil array of the other group. The response of the sonde is obtained by combining the responses detected in several groups of receivers at different depths. Combination sondes, including those capable of performing both induction and sonic logging may be constructed.