On: “The electrical field in a borehole with a casing,” by A. A. Kaufman (January 1990 GEOPHYSICS, 55, p. 29–38) and “A transmission line model for electrical logging through casing,”

Abstract

In two interesting papers (Kaufman, 1990; and Kaufman and Wightman, 1993), it is proposed that D.C. (direct current) flow in a cased borehole can be described by a transmission‐line model. This important conjecture is given considerable support by these authors in their analysis. I have found a relatively simple and straightforward formulation, using a modal approach, that gives further insight.