| One of the most challenging problems in the field of electromagnetic well logging is the development of interpretation methods for the characterization of conductivity anisotropy in an earth formation. Response of a triaxial electromagnetic induction well logging instrument is examined. This instrument detects three components of the magnetic field due to each of three transmitters for a total of nine signals. The conductivity anisotropy of the medium can be resolved from the instrument response. This information includes not only the vertical and horizontal conductivities, but also the orientation of the logging instrument axis with respect to the principal tensor axes. Formulas for the apparent horizontal and vertical conductivities, the apparent anisotropy coefficient, and the apparent relative deviation angle are introduced.; A new method of induction logging based on electrical measurements is investigated. Electrical tensor components are studied in an unbounded, homogeneous, transversely isotropic, conductive medium. Low frequency asymptotic approximations of the analytical solution are derived. The important result is that by measuring the in-phase components of the electrical tensor, the principal values of the conductivity tensor can be obtained.; The basic principles of tensor induction logging two-, three-, and multilayer anisotropic formations in vertical and deviated wells are examined by using numerical simulation of the tensor logs. A technique for correct reconstruction of the apparent conductivities of the anisotropic formations is introduced, based on application of a regularized Newton method. The method is fast and provides real time interpretation. The practical effectiveness of this technique for tensor induction log interpretation is illustrated using results of numerical experiments.; The theoretical formulas for the tensor apparent conductivities of the transversely isotropic medium are studied and developed for an ideal tensor induction instrument with coinciding positions of three mutually orthogonal transmitters at one point and all three receivers at the other point in a borehole. Formulas can be corrected for practical instrument design. Corrected formulas for a practical tensor induction well logging instrument are introduced. The numerical study shows, that for various anisotropy values, corrected apparent conductivities are practically the same as the theoretical apparent parameters.; A new technique for interpretation of tensor induction well logging (TIWL) data is presented. This method is called sharp boundary inversion, based on using specially selected stabilizing functionals, which minimize the area where strong model parameter variations and discontinuities occur. The method recovers the sharp boundary between various anisotropic geoelectrical layers and reconstructs both horizontal and vertical resistivity profiles.; The new TIWL interpretation methods are illustrated by application to the synthetic models of layered anisotropic formations. These methods are applied to the typical benchmark petrophysical models. |
