Abstract: An apparatus and a method for recording the magnetic induction tensor induced in an earth formation are provided. The apparatus includes a magnetic induction device having at least three mutually orthogonal transmitter dipoles and at least three mutually orthogonal receiver dipoles that are direct-coupled, and at least three mutually orthogonal receiver dipoles that are cross-coupled. The method includes using the apparatus to sample the magnetic induction tensor components at a point. Further, samples may be taken at regularly spaced intervals using the magnetic induction device, moving the triaxial logging unit so that each transmitter and each receiver sequentially occupy the same point, repeating these steps until each transmitter and receiver array have sequentially occupied all desired points, and combining the magnetic induction tensor components to form the magnetic induction tensor. These components are useful in inferring water saturation and estimating hydrocarbon volumes in petroleum reservoirs.

Abstract: An apparatus and a method for recording the magnetic induction tensor induced in an earth formation are provided. The apparatus comprises a magnetic induction device having at least three mutually orthogonal transmitter dipoles and at least three mutually orthogonal receiver dipoles that are direct-coupled, and at least three mutually orthogonal receiver dipoles that are cross-coupled. The method comprises using the apparatus to sample the magnetic induction tensor components at a point. Further, samples may be taken at regularly spaced intervals using the magnetic induction device, moving the triaxial logging unit so that each transmitter and each receiver sequentially occupy the same point, repeating these steps until each transmitter and receiver array have sequentially occupied all desired points, and combining the magnetic induction tensor components to form the magnetic induction tensor. These components are useful in inferring water saturation and estimating hydrocarbon volumes in petroleum reservoirs.

Abstract: Apparatus for 360.degree. azimuthal imaging of steel casing employs a transducer that is rotated around the inside wall of the casing for inducing and measuring variations in induced flux density within the casing as an indication of changes in casing thickness.

Abstract: A cylindrical core sample of a subterranean formation is place into a sleeve under confining pressure. At least one electrode array extends through the sleeve and makes contact with the core sample. The array is in a plane normal to the core sample and has an even number of electrodes equally spaced about the sleeve. A current is passed through the core sample and voltages are measured across each pair of electrodes that are spaced 180.degree. apart around the sleeve. Such measurements are utilized to identify the radial direction of any electrical anisotropy in the core sample, particularly under differing fluid saturation conditions.

Abstract: A transversely isotropic cylindrical core sample of a subterranean formation is fluid saturated and subjected to a confining pressure. Electrical potential is measured along the core sample and in a plurality of direction through the core sample which are normal to the cylindrical axis of the core sample at a plurality of spaced-apart positions along such axis. From these electric potential measurement tensor conductivity components normal to and lying within the bedding plane of the core sample are determined.

Abstract: A cylindrical core sample of a subterranean formation is fluid saturated and subjected to a confining pressure. Voltages are measured in a plurality of directions through the core sample which are normal to the cylindrical axis of the core sample at a plurality of spaced-apart positions along such axis and utilized to determine resistivities. These resistivities are compared to identify the radial direction of any electrical anisotropy in the core sample for differing fluid saturation conditions.

Abstract: A core sample from a subterranean formation is shaped to provide a plurality of parallel, planar outer surfaces. Electrical resistivity is measured in each of the azimuthal directions through the core sample which are perpendicular to each of the pairs of parallel, planar outer surfaces for each of a plurality of differing fluid saturations within the core sample. A logarithmic plot is made of measured resistivity versus water saturation for each of the azimuthal directions through the core sample for which resistivity was measured. If the same logarithmic plot is obtained for all measured azimuthal directions, the core sample is identified as being electrically isotropic. If different logarithmic plots are obtained for at least 2 azimuthal directions the core sample is identified as being electrically anisotropic.