Abstract: Methods and devices used to calibrate EM corrosion detection tools may estimate the effects of the presence of a core on measurements to enable more accurate corrosion detection in the well line. The methods may involve sending voltages to a core of a well tool disposed in the well line to obtain signals while the core is in a saturated and unsaturated state. Subsequent measurements using the core may be calibrated using a constant resulting from the division of the signals achieved at the core in the saturated and unsaturated states.

Abstract: Aspects of the subject technology relate to systems and methods for identifying values of mud and formation parameters based on measurements gathered by an electromagnetic imager tool through machine learning. One or more regression functions that model mud and formation parameters capable of being identified through an electromagnetic imager tool as a function of possible tool measurements of the electromagnetic imager tool can be generated using a known dataset associated with the electromagnetic imager tool. One or more tool measurements obtained by the electromagnetic imager tool operating to log a wellbore can be gathered. As follows, one or more values of the mud and formation parameters can be identified by applying the one or more regression functions to the one or more tool measurements.

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: A well monitoring system includes a plurality of transmitter coils coupled to an exterior of a casing positioned within a wellbore, wherein one or more first transmitter coils are positioned at a first location and one or more second transmitter coils are positioned at a second location axially offset from the first location. At least one receiver coil is coupled to the exterior of the casing and positioned at the second location. A power source is communicably coupled to the one or more first and second transmitter coils. The one or more first transmitter coils generates a magnetic field detectable by the at least one receiver coil, and the one or more second transmitter coils generates a bucking signal that minimizes a direct coupling between the one or more first transmitter coils and the at least one receiver coil.

Abstract: A system and method according to which a downhole component positioned behind a casing is powered, the casing extending within an oil and gas wellbore that traverses a subterranean formation. Powering the downhole component may include inducing an electrical current to flow in the casing; permitting the electrical current to flow out of the casing to create a first potential difference between a first point and a second point spaced therefrom, the first and second points being located behind the casing; utilizing the first potential difference to store electrical power; and supplying the stored electrical power to the downhole component positioned behind the casing to thereby power the downhole component. The system may include a power source in electrical communication with the casing; a power harvester positioned behind the casing and in electrical communication with the downhole component; and a current return unit in electrical communication with the power source.

Abstract: A method includes deploying an electromagnetic (EM) defect detection tool in a borehole having one or more tubular strings. The method also includes collecting measurements by the EM defect detection tool as a function of measured depth or position. The method also includes using the measurements and a first inversion process to determine a defect in the one or more tubular strings. The first inversion process involves a cost function having a misfit term and having a stabilizing term with nominal model parameters. The method also includes performing an operation in response to the determined defect.

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 corrosion detection system for a pipe may include a corrosion detection tool. The corrosion detection tool may include a transmitter and a receiver. The transmitter and receiver have measurements associated with each and these measurements may be used to determine an impedance. Derived constants match a numerical model that is based on the measurements associated with the transmitter and the nominal thickness of the pipe. The information related to the thickness of a pipe surrounding the corrosion detection is based on the derived constants and the impedance. This thickness of the pipe may be used to determine if a section of a pipe has a defect, such as, corrosion.

Abstract: Eddy current logging enables corrosion monitoring in nested-pipe arrangements. An illustrative method of logging total thickness of the pipe walls includes acquiring measurements from an electromagnetic logging tool conveyed through the innermost bore, each measurement associated with a TRF combination (transmit antenna, receive antenna, and frequency), and further associated with a position along the bore. Multiple scale factors are applied to the measurements to determine multiple total thickness estimates for each position, each of the multiple scale factors corresponding to a subset of single-pipe defect profiles. Preferably, every possible single-pipe defect profile is included in at least one of these subsets. A total thickness log value for each position is derived from the multiple total thickness estimates for that position, and the derived total thickness log values are used to update a displayed total thickness log as the measurements are being acquired.

Abstract: Eddy current logging enables corrosion monitoring in nested-pipe arrangements. An illustrative method of logging total thickness of the pipe walls includes acquiring measurements from an electromagnetic logging tool conveyed through the innermost bore, each measurement associated with a TRF combination (transmit antenna, receive antenna, and frequency), and further associated with a position along the bore. Multiple scale factors are applied to the measurements to determine multiple total thickness estimates for each position, each of the multiple scale factors corresponding to a subset of single-pipe defect profiles. Preferably, every possible single-pipe defect profile is included in at least one of these subsets. A total thickness log value for each position is derived from the multiple total thickness estimates for that position, and the derived total thickness log values are used to update a displayed total thickness log as the measurements are being acquired.

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: Various embodiments include apparatus and methods implemented to monitor detection of a flood front of a waterflood in a formation. Embodiments can include control of current in a set of three current electrodes to inject current into a formation around a pipe in a wellbore, where the three current electrodes include two of the electrodes to inject current and the third electrode to operatively provide a current return. Response of the formation to the current injections can be communicated by interrogating an optical fiber that extends along a longitudinal axis of the pipe. Determination of progression of the waterflood with respect to the wellbore can be provided from controlling the current and interrogating the optical fiber over time. Additional apparatus, systems, and methods are disclosed.

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: A system can include a current source electrically connected to casing in a wellbore, and a sensor including a monitoring electrode, a potential difference between the casing and the electrode resulting from current applied by the current source, and the potential difference indicating an impedance of a substance in an annulus external to the casing. A method can include positioning sensors spaced apart along a casing in a wellbore, each of the sensors including an electrode in electrical contact with a substance in an annulus, inducing current in the casing, and measuring a potential difference between the casing and the electrode at each sensor. Another system can include a current source, the current source being electrically connected to casing in a wellbore, and a sensor including a monitoring electrode and an electro-optical transducer that converts a potential difference between the casing and the electrode into strain in an optical waveguide.

Abstract: The operational position of a moveable device is detected using an electromagnetic induction 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: Apparatus and methods to investigate a multiple nested conductive pipe structure can be implemented in a variety of applications. An electromagnetic pulsed tool disposed in the multiple nested conductive pipe structure in a wellbore can make a set of log measurements and provide a measured log at different depths in the multiple nested conductive pipe structure. A test setup or library can provide a set of small defect log measurements. Processing circuitry can process the set of log measurements to generate thickness estimations of the multiple nested conductive pipes and processing circuitry can process the set of small defect log measurements to generate small defect thickness estimations. Processing circuitry can solve a system of equations involving the thickness estimations and the small defect thickness estimations to generate thickness variations for the multiple nested conducted pipes over the different depths. 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: 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: 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: 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.