Some effects of formation anisotropy on resistivity measurements in boreholes

Abstract

Abstract It is shown that a wide class of potential problems involving anisotropic media can be transformed into equivalent problems involving only isotropic media. By means of such transformations it is possible, in a large number of cases, to determine the apparent resistivities which would be observed in anisotropic formations, using electrode-type resistivity logging devices. Discussion is given of an infinite, anisotropic medium with and without borehole, of two semi-infinite anisotropic beds (without borehole), and of a thin isotropic bed bounded by anisotropic adjacent formations (without borehole). An interpretation chart for the normal device is presented for thick, non-invaded, anisotropic beds penetrated by a borehole.