Abstract: A calibration system for an electromagnetic (EM) tool includes a processor. The processor employs the EM tool to measure responses at each of a plurality of channels. The processor records the measured responses at each of the channels in an EM data log for the channel. The processor determines a nominal value of each of the channels, as being equal to a histogram peak of the EM data log. The processor selects one or more calibration points from the EM data log for a particular channel, based on a difference between the nominal value of the particular channel and the measured response at the calibration point being greater than a particular threshold. The processor determines a plurality of parameters by reducing a misfit between synthetic data and both the nominal values of the channels and the measured responses of the channels at the selected one or more calibration points.

Abstract: A method includes deploying an electromagnetic (EM) defect detection tool in a downhole environment having a plurality of tubular strings with different diameters. The method also includes receiving raw measurements collected by the EM defect detection tool. The method also includes deconvolving the raw measurements with another input to obtain deconvolved raw measurements. The method also includes using the deconvolved raw measurements to determine a defect in at least one of the plurality of tubular strings. The method also includes performing, by a device, an operation in response to the determined defect.

Abstract: Apparatus, systems, and methods may operate to detect rugosity in a borehole. Additional activity may include generating a rugosity correction, responsive to detecting rugosity in the borehole, by finding an effective borehole diameter, consistent with the presence of rugosity, for which a simulation of a model of the borehole using the effective borehole diameter generates simulation resistivity measurements that match, within a tolerance, resistivity measurements before execution of a borehole correction algorithm. Additional activity may include applying rugosity correction by generating resistivity logs, using the effective borehole diameter, that are corrected for rugosity and borehole effect. Additional apparatus, systems, and methods are disclosed.

Abstract: Methods and systems of electromagnetic sensing in a wellbore are presented in this disclosure for monitoring annulus fluids and water floods. An array of transmitters and one or more receivers are located along a casing in the wellbore. A transmitter in the array and one of the receivers can be mounted on a same collar on the casing forming a transmitter-receiver pair. The receiver can receive a signal originating from the transmitter and at least one other signal originating from at least one other transmitter in the array, wherein the signal is indicative of a fluid in the wellbore in a vicinity of the transmitter-receiver pair and the at least one other signal is indicative of another fluid in a formation around the wellbore. The receiver can further communicate, via a waveguide, the signal and the at least one other signal to a processor for signal interpretation.

Abstract: The operational position of a moveable device is detected using a magnetic-type logging tool. The logging tool generates a baseline log of the moveable device in a non-actuated position, and a response log of the moveable device in an actuated position. The baseline and response logs are then compared in order to determine the operational position of the moveable device.

Abstract: An example system includes an electrode-based tool for deployment in a downhole environment. The electrode-based tool has a plurality of current electrodes, at least one voltage monitoring electrode, at least one return electrode, and electronics to collect one or more voltage measurements from the at least one voltage monitoring electrode as current from at least one of the plurality of current electrodes is injected into the downhole environment and flows to the at least one return electrode. The system also includes at least one processor to estimate leakage current between at least one of the plurality of current electrodes and the at least one return electrode based on the collected one or more voltage measurements and a predetermined internal impedance model or table. The at least one processor is configured to derive a corrected downhole environment parameter based at least in part on the estimated leakage current.

Abstract: Metamaterials are used in well logging measurement tools to position-shift and size-scale antennas such that they can be placed very close to the outer perimeter of the tool, which can improve azimuthal sensitivity and vertical resolution. Antennas of an azimuthal pipe inspection or induction-based borehole imaging tool can be placed with minimal stand-off against a borehole wall. Use of such metamaterials can improve the resolution of logs or images that are obtained by such tools. The metamaterials also can be used to effectively centralize radial coils. Disclosed implementations of metamaterials can be used with gradient ranging tools to effectively increase the spacing between ranging antennas. Increased spacing can maximize the signal levels with respect to noise, without producing distortions that are observed with the inclusion of magnetic materials.

Abstract: An example system includes an electrode-based tool for deployment in a downhole environment, where the electrode-based tool having a plurality of current electrodes, at least one voltage monitoring electrode, at least one return electrode. The electrode-based tool also includes electronics to measure leakage current between at least one of the plurality of current electrodes and the at least one return electrode as current from at least one of the plurality of current electrodes is injected into the downhole environment and flows to the at least one return electrode. The system also includes at least one processor configured to derive a corrected downhole environment parameter based at least in part on the measured leakage current.

Abstract: An example calibration method for a galvanic tool may include determining an internal coupling impedance between at least two electrodes of the galvanic tool, and inputting the determined internal coupling impedances into an equation used to evaluate the response of the tool. Voltage and current measurements may be generated from the galvanic tool using a calibration device. A leakage current value through at least one of the two electrodes may be determined based, at least in part, on the voltage and current measurements and the equation. The leakage current may be stored.

Abstract: An apparatus and method may operate to mount one or more communication assemblies relative to the exterior of a casing being placed in a borehole. Each communication assembly is configured to cause electrodes of a fluid sensing assembly to inject currents into fluids in one or more regions of the annulus surrounding the casing, and to obtain excitation responses from electrodes of the fluid sensing assembly, where the excitation responses vary based on electrical properties of fluids in one or more regions of the annulus surrounding the casing. Control is provided to control which electrodes of the fluid sensing assembly will inject currents and generate excitation responses and to control which electrodes of the fluid sensing assembly will sense the currents. Additional apparatus, systems, and methods are disclosed.

Abstract: An electromagnetic field measuring device utilizes metamaterials to manipulate electromagnetic fields. Such a device is useful in a variety of applications including, for example, downhole gradiometric ranging.

Abstract: An example method may include computing a database for an ideal representation of a galvanic tool, and determining internal coupling impedance between at least one monitor electrode of the galvanic tool and a reference. Voltage and current measurements from the galvanic tool positioned within a formation may be received. A formation resistivity from the voltage and current measurements may be calculated based, at least in part, on the database and the determined internal coupling impedances.

Abstract: An example calibration method for a galvanic tool may include determining an internal coupling impedance between at least two electrodes of the galvanic tool, and inputting the determined internal coupling impedances into an equation used to evaluate the response of the tool. Voltage and current measurements may be generated from the galvanic tool using a calibration device. A leakage current value through at least one of the two electrodes may be determined based, at least in part, on the voltage and current measurements and the equation. The leakage current may be stored.

Abstract: The disclosure concerns an electromagnetic logging tool for recording the electromagnetic properties of a subterranean rock formation. One version of the disclosure includes an electromagnetic transmitter that transmits an electromagnetic signal into a downhole formation, an electromagnetic receiver that receives the electromagnetic signal formation; and a cavity antenna in which the interior of the cavity contains a metamaterial made up of a plurality of unit cells that include split ring resonators or other devices such as electric-LC resonators.

Abstract: Metamaterials are used in well logging measurement tools to provide high directionality galvanic and induction tools having metamaterial focusing. Using metamaterial lenses, currents injected by galvanic tools can be focused in both axial and azimuthal directions. In addition, the focus plane can be shifted away from the tool body into a borehole formation, making measurements more sensitive to zones of interest and less sensitive to boreholes and invaded zones. Another metamaterial lens can bend injected currents toward the head of the tool, adding a look-ahead functionality.

Abstract: The disclosure concerns a device for obtaining electromagnetic measurements in a wellbore. In one implementation, the device includes an electromagnetic source carried by the device and a metamaterial arranged to cover a portion of the device in order to divert electromagnetic waves from the source around the covered portion of the device. In one version, the electromagnetic radiation from the source impinging on the portion of the device covered by the metamaterial, and on the electronics carried by the devices that are covered by the metamaterial is reduced. Depending on the implementation, the electromagnetic source may be an antenna, such as a coil antenna. Also, the antenna coil may be wrapped circumferentially around the tool.