Abstract: Various embodiments include apparatus and methods of operation with respect to well logging. Apparatus and methods include a tool having an arrangement of transmitters and receivers that are operated at different positions downhole and a processing unit to process collected signals such that the arrangement of transmitters and receivers provides measurements that mimic operation of a different arrangement of transmitters and receivers. Additional apparatus, systems, and methods are disclosed.

Abstract: Systems and methods for performing bed boundary detection and azimuthal resistivity logging using a logging tool with a pair of tilted receiver antennas having a midpoint on a longitudinal axis of the logging tool, a first pair of transmitter antennas symmetrically spaced from said midpoint, and a third tilted receiver antenna positioned farther from said midpoint than the transmitter antennas. Method embodiments include energizing each transmitter antenna of the first pair in a firing sequence and obtaining, responsive to the energizing, measurements with a pair of tilted receiver antennas equally spaced from said midpoint. Methods may also include obtaining, responsive to energizing of a more distant one of the first pair of transmitter antennas, measurements with a third tilted receiver antenna positioned farther from the midpoint than the transmitter antennas.

Abstract: Systems and methods for performing bed boundary detection and azimuthal resistivity logging with a single tool are disclosed. Some method embodiments include logging a borehole with an azimuthally-sensitive resistivity logging tool; deriving both a resistivity log and a boundary detection signal from measurements provided by said tool; and displaying at least one of the boundary detection signal and the resistivity log. The resistivity log measurements may be compensated logs, i.e., logs derived from measurements by one or more symmetric transmitter-receiver arrangements. Though symmetric arrangements can also serve as the basis for the boundary detection signal, a greater depth of investigation can be obtained with an asymmetric arrangement. Hence the boundary detection signal may be uncompensated.

Abstract: Device, system, and method embodiments provide fluid front monitoring via permanent, casing-mounted electromagnetic (EM) transducers. One or more casing strings have one or more transmit antennas that each encircle a casing string and one or more receive antennas that similarly encircle the casing string, with at least one receive antenna oriented differently from at least one transmit antenna to provide sensitivity to at least one cross-component signal. A processor unit derives an estimated distance to a fluid front, and may further determine a direction and orientation of the fluid front for display to a user. Signals from an array of transmit and receive antennas may be combined, optionally with signals from other boreholes, to locate and track multiple points on the fluid front. In response to the determined location and progress of the front, the processor unit may further provide control settings to adjust injection and/or production rates.

Abstract: Various resistivity logging tools, systems, and methods are disclosed. At least some system embodiments include a logging tool and at least one processor. The logging tool provides transmitter-receiver coupling measurements that include at least direct coupling along the longitudinal tool axis (Czz), direct coupling along the perpendicular axis (Cxx or Cyy), and cross coupling along the longitudinal and perpendicular axes (Cxz, Cyz, Czx, or Czy). The processor performs a multi-step inversion of said transmitter-receiver coupling measurements to obtain values for model parameters. Based at least in part on the model parameters, the processor determines borehole corrections for the transmitter-receiver coupling measurements and may further provide one or more logs derived from the borehole corrected transmitter-receiver coupling measurements.

Abstract: A casing segment includes a conductive tubular body and at least one transmission crossover arrangement. Each transmission crossover arrangement has an inductive adapter in communication with a coil antenna that encircles an exterior of the tubular body.

Abstract: A multilateral production control method includes casing a first borehole with a casing tubular having at least one transmission crossover arrangement, each transmission crossover arrangement having an adapter in communication with a coil antenna that encircles the casing tubular. The method also includes completing a second borehole with an inflow control device. The method also includes deploying, inside the casing tubular, a conductive path that extends from a surface interface to the at least one transmission crossover arrangement. The method also includes communicating between the surface interface and the inflow control device using the at least one transmission crossover arrangement.

Abstract: An interwell tomography method includes casing a first borehole with a casing tubular having at least one transmission crossover arrangement, each transmission crossover arrangement having an adapter in communication with a coil antenna that encircles an exterior of the casing tubular. The method also includes deploying, inside the casing tubular, a conductive path that extends from a surface interface to the at least one transmission crossover arrangement. The method also includes providing a set of one or more antennas in a second borehole. The method also includes obtaining electromagnetic (EM) measurements for interwell tomography using the at least one transmission crossover arrangement and the set of one or more antennas, where said obtaining involves conveying data or power between the at least one transmission crossover arrangement and the surface interface via the conductive path.

Abstract: An interwell tomography method includes casing a first borehole with a casing tubular having at least one transmission crossover arrangement, each transmission crossover arrangement having an adapter in communication with a coil antenna that encircles an exterior of the casing tubular. The method also includes deploying, inside the casing tubular, a conductive path that extends from a surface interface to the at least one transmission crossover arrangement. The method also includes providing a set of one or more antennas in a second borehole. The method also includes obtaining electromagnetic (EM) measurements for interwell tomography using the at least one transmission crossover arrangement and the set of one or more antennas, where said obtaining involves conveying data or power between the at least one transmission crossover arrangement and the surface interface via the conductive path.

Abstract: Logging tools and methods for obtaining a three-dimensional (3D) image of the region around a borehole. In at least some embodiments, a 3D imaging tool rotates, transmitting pulses that are approximately a nanosecond long and measuring the time it takes to receive reflections of these pulses. Multiple receivers are employed to provide accurate triangulation of the reflectors. In some cases, multiple transmitters are employed to obtain compensated measurements, i.e., measurements that compensate for variations in the receiver electronics. Because reflections occur at boundaries between materials having different dielectric constants, the 3D imaging tool can map out such boundaries in the neighborhood of the borehole. Such boundaries can include: the borehole wall itself, boundaries between different formation materials, faults or other discontinuities in a formation, and boundaries between fluids in a formation.

Abstract: Various resistivity logging tools, systems, and methods are disclosed. At least some system embodiments include a logging tool and at least one processor. The logging tool provides transmitter-receiver coupling measurements that include at least direct coupling along the longitudinal tool axis (Czz), direct coupling along the perpendicular axis (Cxx or Cyy), and cross coupling along the longitudinal and perpendicular axes (Cxz, Cyz, Czx, or Czy). The processor performs a multi-step inversion of said transmitter-receiver coupling measurements to obtain values for model parameters. Based at least in part on the model parameters, the processor determines borehole corrections for the transmitter-receiver coupling measurements and may further provide one or more logs derived from the borehole corrected transmitter-receiver coupling measurements.

Abstract: Various embodiments include apparatus and methods to detect and locate conductive structures below the earth's surface. Tools can be configured with receiving sensors arranged to receive signals generated from a conductive structure in response to a current flowing on the conductive structure. Magnetic-related values from the signals can be processed, relative to the tool, to determine a position of a conductive structure from which the signal was generated in response to current flowing on the conductive structure. Additional apparatus, systems, and methods are disclosed.

Abstract: Methods and systems that compensate for magnetic interference in azimuthal tool measurements. At least some method embodiments include a downhole logging method that includes taking measurements as a function of orientation from inside a borehole. The measurements are associated with different azimuthal bins, and an azimuthal direction is determined for each azimuthal bin. Because the tool rotates at a constant rate, the relative number of measurements associated which the different bins can be used to measure the effective sizes of the different bins and to redetermine the effective angles of the bins in the presence of magnetic interference. The tool measurements may include, but are not limited to, formation resistivity, magnetic field, and formation density.

Abstract: Apparatus and methods are implemented to determine characteristics of geological formations in a well. One or more transmitters and receivers electrically imitate a moving antenna. The moving antenna produces a distribution of frequencies by utilizing the Doppler effect. Each anomaly in the well produces reflections with different frequency, amplitude and phase information. Location and characteristics of multiple anomalies can be identified simultaneously in a well.

Abstract: Various embodiments include apparatus and methods to detect and locate conductive structures below the earth's surface. Tools can be configured with receiving sensors arranged to receive signals generated from a conductive structure in response to a current flowing on the conductive structure. Magnetic-related values from the signals can be processed, relative to the tool, to determine a position of a conductive structure from which the signal was generated in response to current flowing on the conductive structure. Additional apparatus, systems, and methods are disclosed.

Abstract: Disclosed herein are electromagnetic resistivity logging systems and methods that employ an antenna configuration having at most two transmitter or receiver antenna orientations that rotate relative to the borehole. The measurements made by this reduced-complexity antenna configuration enable the determination of at least seven components of a coupling matrix, which may be determined using a linear system of equations that express the azimuthal dependence of the measurements. For increased reliability, measurement averaging may be performed in azimuthally spaced bins. The coupling matrix components can then be used as the basis for determining logs of various formation parameters, including vertical resistivity and anisotropy.

Abstract: Various embodiments include apparatus and methods of determining resistivity of fluids downhole in a well. The apparatus and methods may include using a sensor that employs a focused electric dipole as a transmitter and a uses a receiver to detect the electric current strength in the fluid under measurement responsive to the transmitter. Additional apparatus, systems, and methods are disclosed.

Abstract: Various logging-while-drilling (LWD) systems and methods provide resistivity logging coupled with deep detection of elongated anomalies at acute angles, enabling effective geosteering without disrupting drilling operations and without requiring intervention in the operations of the existing well. One LWD system embodiment employs a tool having tilted antennas as the transmitter and the receiver, where at least one of the antennas is placed in the vicinity of the bit, making it possible to detect existing wells at distances of 50-100 feet. In some cases, the detection distance is increased by enhancing the visibility of the existing well using a contrast fluid treatment on target well, either to fill the bore or to surround the well with treated cement or fluids that invade the formation. At least one inversion method separates the inversion of formation parameters from the inversion of parameters specifying distance, direction, and orientation of the existing well.

Abstract: Disclosed herein are electromagnetic resistivity logging systems and methods that employ an antenna configuration having at most two transmitter or receiver antenna orientations that rotate relative to the borehole. The measurements made by this reduced-complexity antenna configuration enable the determination of at least seven components of a coupling matrix, which may be determined using a linear system of equations that express the azimuthal dependence of the measurements. For increased reliability, measurement averaging may be performed in azimuthally spaced bins. The coupling matrix components can then be used as the basis for determining logs of various formation parameters, including vertical resistivity and anisotropy.

Abstract: Various embodiments include apparatus and methods of operation with respect to well logging. Apparatus and methods include a tool having an arrangement of transmitters and receivers to capture a signal from a first region relative to the tool such that signal contributions from a second region relative to the tool are cancelable, based on placement of the transmitters and receivers with respect to each other. Additional apparatus, systems, and methods are disclosed.