Directional induction logging for evaluating layered magnetic formations

We present a modeling study to investigate the ability of directional induction logging to evaluate magnetic properties of formations. Simultaneous measurement of in-phase and quadrature components of electromotive force, or R- and X-signals, respectively, gives complete information about both the electrical resistivity and the magnetic susceptibility of the formation. We describe an approach for designing a directional induction tool with tilted transmitting and receiving coils. We discuss spatial resolution using directional excitation-measurement and evaluation of formation parameters. The proposed method can detect magnetic susceptibility inhomogeneity in addition to electrical resistivity inhomogeneity using the X-signal. The X-signal log response reflects abrupt changes in magnetic properties, with sharp gradients located in the vicinity of magnetic susceptibility interfaces.