Abstract: A method and system for resistivity imaging. A method may comprise disposing a downhole tool into a borehole, applying a voltage difference between the array of injector electrodes, constructing a first set of formation images for each of the plurality of frequencies, applying a mud effect removal algorithm to produce a second set of formation images for each of the plurality of frequencies, applying a dielectric correction algorithm to each of the plurality of frequencies to produce a third set of formation images for each of the plurality of frequencies, and combining the first set of formation images, the second set of formation images, and the third set of formation images to obtain a blended image. A system for resistivity imaging may comprise a downhole tool. The downhole tool may comprises a pad, an array of injector electrodes, and one or more return electrodes.

Abstract: Pipe]parameter determinations from electromagnetic logs can be improved, in accordance with various embodiments, by weighting signals with frequencies below a threshold associated with resolution degradation lower than signals with frequencies above the threshold. The threshold frequency may be determined based on a spatial resolution associated with the logging tool and a logging speed. Further embodiments are described.

Abstract: A method for identifying an operating frequency may comprise performing a frequency sweep using one or more injector electrodes disposed on a downhole tool, recording one or more measurements from the frequency sweep, identifying one or more stable frequencies from the frequency sweep, and identifying one or more operating frequencies from the one or more stable frequencies. A system for electrical isolation may comprise a downhole tool, a pad, an arm, wherein the arm is attached to the mounting bracket and the mandrel, and an information handling system connected to the pad through the first set of electronics and the second set of electronics. The downhole tool may comprise a mandrel, a chassis disposed in the mandrel, and a first set of electronics disposed in the chassis.

Abstract: Apparatus and methods can be implemented to monitor the condition of the production and intermediate casing strings in oil and gas field operations. A series of measurements can be made in a multi-pipe structure and received responses can be operated on by employing a mapping optimization procedure in which a surrogate model is updated. Estimates of one or more properties of the pipes of the multi-pipe structure can be generated using coefficients of the updated surrogate model. Additional apparatus, systems, and methods are disclosed.

Abstract: A method and system for estimating a mud angle. A method may include disposing a downhole tool into a borehole, energizing a button array, transmitting a current from the electrode into a formation, recording the current from the formation with a return electrode to obtain a plurality of measurements, identifying at least one low resistivity zone from the plurality of measurements to produce a measurement set, inverting the measurement set to find a mud angle vector, removing the mud angle vector from the measurement set to obtain a corrected measurement, and obtaining an electrical image using the corrected measurement. A system may include a downhole tool, a conveyance, and an information handling system. The downhole tool may further include at least one electrode and at least one return electrode.

Abstract: A system includes a tool to dispose in a wellbore lined with pipe. The tool includes first and second receiver coils having a non-uniform winding along a longitudinal axis, a third receiver coil having a non-uniform winding coaxial with at least one of the first and second receiver coils, and a transmitter. The system includes a processor to execute instructions to perform operations including causing the transmitter to emit an induced magnetic field, measuring the induced magnetic field using the first receiver coil to create a first measurement and using the first and second receiver coils to create a second measurement. The operations include determining a static magnetic field, selecting the first or second measurement based on a magnitude of the static magnetic field to determine a selected measurement, and determining at least one property of the pipe using the selected measurement.

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 inspection tool apparatus includes a core having an axial length. The axial length is determined based on a desired depth of inspection radially from the core. A plurality of arms are coupled to and extend radially from the core. The core and the plurality of arms comprise a high permeability magnetic material. The core or at least one of the plurality of arms is wound by a respective coil that is positioned to receive magnetic flux that is passing through the core or at least one of the plurality of arms.

Abstract: A method and system for resistivity imaging. A method may comprise disposing a downhole tool into a borehole, applying a voltage difference between the array of injector electrodes, constructing a first set of formation images for each of the plurality of frequencies, applying a mud effect removal algorithm to produce a second set of formation images for each of the plurality of frequencies, applying a dielectric correction algorithm to each of the plurality of frequencies to produce a third set of formation images for each of the plurality of frequencies, and combining the first set of formation images, the second set of formation images, and the third set of formation images to obtain a blended image. A system for resistivity imaging may comprise a downhole tool. The downhole tool may comprises a pad, an array of injector electrodes, and one or more return electrodes.

Abstract: A logging tool having a transmitter and receiver is positioned in a geological formation. While the logging tool is static, a transmit input signal is applied to a transmitter to cause the transmitter to induce a transmit output signal in the form of an electromagnetic field into a formation. While the logging tool is static, a formation signal is received based on the transmit output signal. The formation signal may be a voltage indicative of an induced polarization in the formation based on the transmit output signal. A complex resistivity of the formation is determined based on the formation signal.

Abstract: The present disclosure relates generally to a system and method for increasing the reliability and data-rate transmission of information from a downhole device to the surface and from the surface to the downhole device. A fluid sampling system may comprise a downhole tool positionable in a wellbore and comprising a fluid testing chamber. The downhole tool may also comprise a light spectrum analysis unit disposed at a surface of the wellbore, wherein the light spectrum analysis unit comprises a detector. The downhole tool may further comprise a fiber optic cable for carrying light from the downhole tool to the light spectrum analysis unit, wherein the fiber optic cable is connected to the downhole tool and the light spectrum analysis unit.

Abstract: A method and system for resistivity imaging. A method may comprise disposing a downhole tool into a borehole, applying a voltage difference between the array of injector electrodes, constructing a first set of formation images for each of the plurality of frequencies, applying a mud effect removal algorithm to produce a second set of formation images for each of the plurality of frequencies, applying a dielectric correction algorithm to each of the plurality of frequencies to produce a third set of formation images for each of the plurality of frequencies, and combining the first set of formation images, the second set of formation images, and the third set of formation images to obtain a blended image. A system for resistivity imaging may comprise a downhole tool. The downhole tool may comprises a pad, an array of injector electrodes, and one or more return electrodes.

Abstract: A method and system for communicating with a bottom hole assembly from the surface. The method may comprise drilling into a formation with the bottom hole assembly, disposing at least one porous pot on the surface, emitting an electromagnetic field from the transmitter, sensing a voltage of the electromagnetic field with the at least one porous pot, and measuring the voltage with the porous pot. A system may comprise a downhole tool, wherein the downhole tool is disposed on the bottom hole assembly, a drill string, wherein the drill string is attached to the bottom hole assembly and a well head, a drill bit, and at least one porous pot, wherein the at least one porous pot is disposed on the surface and wherein the at least one porous pot is configured to sense and measure a voltage from the electromagnetic field.

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 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.

Abstract: Apparatus and methods can be conducted in a multi-pipe structure to determine eccentricity of one or more pipes of the multi-pipe structure. A tool having a center axis as a symmetry axis of the tool can be used in which receivers are arranged as a number of pairs of receivers around the center axis of the tool. Each receiver of a pair can be disposed opposite the other receiver of the pair with respect to the center axis such that each pair is symmetrical with respect to the center axis of the tool. Eccentricity of one or more pipes of the multi-pipe structure can be determined based on the received responses at the receivers of the pairs.

Abstract: Described are tools, systems, and methods for dielectric logging using transient waveforms. In some embodiments, one or more microstrip antennas are employed for the measurements. In various embodiments, the waveforms are processed in the time-domain to determine the dielectric properties of a formation, from which geophysical formation properties can then be derived. Further embodiments are disclosed.

Abstract: A multi-string monitoring system that includes a processor. The processor obtains electromagnetic (EM) log measurements of a well having at least one inner tubing string and at least one outer tubing string, the measurements including first channel measurements for higher resolution and second channel measurements for deeper penetration. The processor inverts the first channel measurements over a characterization region of the well and the second channel measurements over the characterization region of the well, to obtain an attribute of the at least one outer tubing string and an attribute of the at least one inner tubing string, based, at least in part, on a first plurality of calibration coefficients and a second plurality of calibration coefficients. The processor stores the attribute of the at least one outer tubing string and the attribute of the at least one inner tubing string as a function of position along the well.

Abstract: A method and a system for determining metal loss in a layered system. The method may comprise disposing an EM metal loss tool downhole, broadcasting an electromagnetic field from the one or more transmitters of the EM metal loss tool into the layered system, recording the altered electromagnetic field with the one or more receivers, processing the signal with an information handling system, and determining metal loss in the layered system. A system may comprise an EM metal loss tool. The EM electromagnetic metal loss tool may comprise at least one transmitter and at least one receiver. The system may further comprise a conveyance, wherein the conveyance is attached to the electromagnetic metal loss tool, and an information handling system, wherein the information handling system is configured to process the altered electromagnetic field and determine metal loss in the layered system.

Abstract: Systems and methods to investigate multi-pipe structures for detection of corrosion and quantitative assessment of thickness in the multiple pipes can be implemented in a variety of applications. Systems can include a set of transmitters and multiple receivers arranged on a tool structure with variable distances to the transmitters of the set of transmitters, where the receivers are arranged to measure electromagnetic responses from a multi-pipe structure to excitation of the set of transmitters with the tool structure disposed in the multi-pipe structure. The electromagnetic responses may include responses correlated to a near field zone, a transition zone, and a far field zone, where the electromagnetic responses can be processed to recover individual thicknesses of each pipe of the multi-pipe structure. Additional apparatus, systems, and methods are disclosed.

Abstract: A method for identifying an operating frequency may comprise performing a frequency sweep using one or more injector electrodes disposed on a downhole tool, recording one or more measurements from the frequency sweep, identifying one or more stable frequencies from the frequency sweep, and identifying one or more operating frequencies from the one or more stable frequencies. A system for electrical isolation may comprise a downhole tool, a pad, an arm, wherein the arm is attached to the mounting bracket and the mandrel, and an information handling system connected to the pad through the first set of electronics and the second set of electronics. The downhole tool may comprise a mandrel, a chassis disposed in the mandrel, and a first set of electronics disposed in the chassis.