1962 Paper J

MODIFICATION OF THE INDUCTION LOG GEOMETRIC FACTOR DUE TO PROPAGATION

Hughes M. Zenor, Professor of Mining Engineering, Missouri School of Mines and Metallurgy

Howard I. Oshry, Director of Research Lane-Wells Company

ABSTRACT

The problem of propagation effects in induction logging has been considered from a phenomenological point of view. Previous theoretical work on this problem has been operational in character, using Maxwell's equations and boundary value techniques. As a result, solutions are available for the simplest plane and cylindrical boundaries.

To attack the practical case of the invaded thin zone with a bore hole in its center, we have divided the formation into toroidal elements coaxial with the bore hole and have considered the interaction of the toroids with the transmitter and receiver of the induction log. The resulting equations have been programmed for solution by a digital computer.

The calculations have been made for a two coil system, but the techniques are applicable to multicoil systems.

The results obtained for the case of the homogeneous medium and for a single interface agree within a few percent with those given by Duesterhoeft.

More complicated cases are under investigation and will be used to prepare correction charts for interpretation.