Visualization of eddy currents induced in an electrically anisotropic formation

Based on a previously developed analytic solution for induction in anisotropic media, we compute the eddy current paths and their associated magnetic fields for both dipping and horizontal sondes. The complex current paths are displayed using three-dimensional visualization techniques in order to better develop a qualitative understanding of the physics involved. The results indicate that electromagnetic induction in a moderately anisotropic formation is characterized by eddy current paths with significant components not only parallel, but also perpendicular, to bedding planes whenever the source magnetic dipole has a significant horizontal component. The associated magnetic fields have a strong component in the direction perpendicular to the bedding planes - a finding that supports the utility of induction sondes that include transversedipole transmitters and receivers to determine formation anisotropy and therefore minimize uncertainty in estimates of hydrocarbon potential.