METHOD AND APPARATUS FOR EDDY CURRENT SUPPRESSION

摘要

An electromagnetic wellbore logging tool including an elongated sonde adapt ed for traversing the wellbore, a source of alternating current, an antenna connected to the source of alternating current, and a receiver circuit connected to the antenna. The receiver circuit provides an output corresponding to electromagnetic signals induced in the antenna. The invention includes at least one insulating insert disposed in a n annular space between the exterior of the sonde and the wall of the wellbore. The insert extends in a direction so as to segment the paths of eddy current which would otherwise flow in the annular space. In a preferred embodiment, the logging tool includes a nuclear magnetic resonance apparatus having a longitudinal dipole antenna. The insulating inserts exten d along the longitudinal axis of the tool so as to segment eddy current paths perpendicular to the longitudinal axis of the tool.