Abstract: A shield apparatus for use in conjunction with a well tool to selectively attenuate one or more electromagnetic energy field components as the components interact with the shield. The shield composed of a flexible strip or conductive body and comprising at least one sloped slot or sloped conductive element therein. The shield being adapted to surround an antenna mounted on a well tool. A method for rotating the axis of the magnetic dipole of a transmitter or receiver coil. A method for winding and shielding an electric coil such that the resultant coil emits or receives selected electromagnetic energy field components.

Abstract: A shield apparatus for use in conjunction with a well tool to selectively attenuate one or more electromagnetic energy field components as the components interact with the shield. The shield composed of a flexible strip or conductive body and comprising at least one sloped slot or sloped conductive element therein. The shield being adapted to surround an antenna mounted on a well tool. A method for rotating the axis of the magnetic dipole of a transmitter or receiver coil. A method for winding and shielding an electric coil such that the resultant coil emits or receives selected electromagnetic energy field components.

Abstract: A method and apparatus for evaluating the resistivity of earth formations surrounding a borehole, particularly high-contrast thin-layer formations or at high dip angles. The method involves positioning a pair of transmitters and a pair of receivers within the borehole, the receivers or transmitters adhering to specific spacing limitations, alternately transmitting electromagnetic energy of a particular frequency and receiving voltage data associated with the transmitted energy. Multiple voltage data are acquired and a representation of a resistivity or conductivity profile is created from a formulated difference of the data from a particular depth and/or neighboring depths. The apparatus forms part of a well logging system including a well tool adapted to be moveable through a borehole. The apparatus being coupled to the well tool and adapted with means to input voltage data developed by the receivers disposed on the well tool.

Abstract: Methods and apparatus for making directional measurements of earth formations surrounding a borehole. New antenna coil shield designs are utilized to provide selective attenuation of at least one electromagnetic energy field component as the component interacts with the shield. The new shields are implemented in several downhole tool configurations to provide azimuthally focused formation measurements. In effect, the new shield filters interacting electromagnetic energy field components to pass those components corresponding to a magnetic dipole oriented at an angle from the tool axis. The shields thereby alter a coil's envelope of influence to electromagnetic energy. The new shields also form part of a system for making directional measurements while drilling.

Abstract: A shielding method and apparatus for an antenna disposed on an elongated support adapted for disposal within a borehole. The shield providing predetermined attenuation of one or more electromagnetic energy field components as the field components interact with the shield. The shield composed of a flexible strip or cylindrical body and respectively comprising a transverse conductive element or a transverse slot therein. The shields being adapted to cover an antenna mounted on the support. The shields being compatible for use in conjunction with saddle, tilted coils or multi-layered tri-axial coils to produce a pure transverse magnetic dipole electromagnetic field. The shields are also used in methods for shielding an antenna disposed on a support to provide predetermined attenuation of an electromagnetic field component as the field components interact with the shield.

Abstract: A logging tool for use in determining the resistivity of an underground formation surrounding a borehole comprises a mandrel with two transmitters spaced apart thereon, each serving to establish a current in the mandrel and in the underground formation. A series of electrodes are spaced along the body between the transmitters and sensors, located at each electrode, measure radial current flow along a path from the mandrel to the underground formation via a respective electrode. Sensors also provide the axial current flowing along the whole mandrel and at positions corresponding to each electrode. A method of determining the formation resistivity includes the steps of measuring the radial currents R.sub.1 R.sub.2 from the mandrel to the formation via each electrode and obtaining the axial currents M.sub.01 M.sub.02 along the mandrel at each electrode due to each transmitter; measuring the total axial current M.sub.

Abstract: An apparatus for determining the resistivity of formations surrounding an earth borehole. An elongated electrically conductive body is movable through the borehole. A first transmitter establishes a first current in the body from a first transmitter position on the body, the first current traveling in a path that includes the body and the formations. An electrode is mounted on the body and has a surface that is electrically isolated from the surface of the body. A first electrical signal, resulting from the first current, is measured at the electrode. A second transmitter establishes a second current in the body from a second transmitter position on the body that is spaced from the first transmitter position, the second current traveling in a path that includes the body and the formations. A second electrical signal, resulting from the second current, is measured at the electrode. A current monitor measures the axial current passing a monitor position on the body to obtain a monitor current value.

Abstract: The disclosed technique and apparatus utilizes the different characteristic responses of a plurality of signals from a propagation or induction well logging device to determine the vertical and horizontal resistivity of formations surrounding a borehole.

Abstract: A disclosed embodiment utilizes one or more toroidal coil antennas mounted, in an insulating medium, on a drill collar to induce currents which travel in a path that includes the drill collar and earth formations around the drill collar. At least one array of electrodes is provided on at least one stabilizer blade of the drill collar and is utilized to detect currents transmitted by toroidal coil antennas which return via the formations to the electrodes laterally; that is, approximately normal to the axis of the drill collar. Signal traces are obtained from measurements taken at respective ones of the transducers, and a dip characteristic of the formations is determined from the signal traces and from signals representing the rotational orientation of the drill collar.

Abstract: Induction logging apparatus is disclosed which depends for its operation not only upon its arrangement of coils, but also upon the skin depth of the formation. The skin effect of the formation is used advantageously by operating a simple induction sonde at a plurality of frequencies simultaneously. Improved depth of investigation and improved vertical resolution result from the invention. Simple arrays are disclosed for the induction logging apparatus. A sonde with a single transmitter and a plurality of two-coil receiver arrays are preferred. The apparatus acquires both the in-phase and quadrature components of each receiver array signal at several frequencies. The response function is shaped by using a multi-channel deconvolution filter.