PROPAGATION EFFECTS IN INDUCTION LOGGING

Abstract

Induction logging utilizes the component of induced receiver coil voltage that is in phase with transmitter coil current as a measure of the conductivity of material surrounding the coils. This paper considers the problem of the field of a vertical magnetic dipole in a horizontally stratified, isotropic conductive formation and shows the receiver coil voltage can be considered as composed of responses due to electromagnetic waves in the formation. These waves which experience attenuation and phase shift as they propagate in the formation are reflected at each interface encountered, and a component of receiver coil voltage is induced for each passage of a wave. The relation of the receiver coil voltage components to the geometric factor of previous analysis is discussed. Universal curves that are useful in determining the response due to unreflected primary and reflected secondary waves are presented Example induction log system responses based on the analysis of the present paper are presented.