Abstract: Systems and methods for corrosion detection of downhole tubulars.

Abstract: Apparatus, systems, and methods may operate to detect anomalous formation resistivity values within measured formation resistivity data, based on mud resistivity associated with a borehole in a geological formation, the measured formation resistivity data comprising the anomalous formation resistivity values and acceptable formation resistivity values. Additional activity may include transforming the anomalous formation resistivity values into corrected formation resistivity values, inverting the corrected formation resistivity values and the acceptable formation resistivity values to provide true resistivity values for a geological formation, and operating a controlled device according to the true resistivity values for the geological formation. Additional apparatus, systems, and methods are disclosed.

Abstract: An example method for modeling a geological formation includes receiving a set of measurements from an electromagnetic logging tool and representing at least one characteristic of the geological formation as at least one continuous spatial function. At least one coefficient of the at least one continuous spatial function may be determined based, at least in part, on the set of measurements. At least one characteristic of the geological formation may be determined based, at least in part, on the at least one continuous spatial function.

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 dielectric logging tool for use in a borehole that penetrates a subsurface formation, includes: at least one wall-contacting face with one or more embedded microstrip antennas including a transmit antenna; an oscillator that supplies a transmit signal; a coherent receiver that measures the one or more scattering coefficients; and a processor that derives a formation property from the one or more scattering coefficients. The tool may be conveyed along a borehole, with the scattering coefficients and derived formation property values associated with tool position and orientation to provide a permittivity log.

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: Systems, methods and apparatuses for measuring properties of a borehole formation and generating an image of the formation. The method comprises selecting a direction for transmission of an electromagnetic signal, wherein the selection includes altering an electromagnetic coupling between an active element of a first device and at least one passive element of the first device. An electromagnetic signal can be transmitted, by the active element of the first device, into a borehole formation. The electromagnetic signal can subsequently be received by a second device. Formation properties can be determined from the received signal and an image of the formation can be generated.

Abstract: A method and system for resistivity imaging may comprise disposing a downhole tool into a borehole, wherein the downhole tool comprises a pad and a plurality of electrodes disposed on the pad, taking an impedance measurement with the plurality of electrodes, applying a correction to the measured impedance by using a relaxation constant of the measured impedance to find a corrected impedance for each electrode of the plurality of electrodes, and constructing an image from the corrected impedance, wherein the image maps formation impedance. The system for resistivity imaging may comprise a downhole tool, a conveyance for disposing the downhole tool in a borehole, and an information handling system. The downhole tool may further comprise an arm and a pad wherein the pad comprises a plurality of electrodes and at least one return electrode.

Abstract: A method for use with a subterranean well can include modeling multiple fluid types in an annulus formed between casing and an earth formation penetrated by a wellbore, inverting electromagnetic data acquired by sensors in the well, and selecting at least one of the fluid types based on the inverting. A system for use with a subterranean well can include multiple sensors longitudinally spaced apart along a casing in a wellbore, each of the sensors imparting electromagnetic impulses to a fluid present in an annulus formed between the casing and the wellbore, and each of the sensors providing observed data indicative of at least one physical property associated with the fluid.

Abstract: Apparatus and techniques are described, such as for obtaining information indicative of a formation resistivity near a casing, such as using an array laterolog apparatus. For example, raw measurements received from a well tool in a borehole near a casing may indicate a resistivity of a geologic formation through which the borehole extends. Any errors or interference in the raw measurements caused by the proximity of the well tool to the casing may be removed to eliminate the casing effect on the raw measurements. In some examples, a signal and formation libraries that include casing specific parameters may be used in conjunction with non-casing optimized signal and formation libraries to perform correction mapping of raw measurements. The corrections and their application to the raw measurements may be based on the position of a well logging tool with respect to a casing termination point.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to estimate a value for a mud cake parameter to provide an estimated mud cake parameter value; to generate, in a solution operation, a formation parameter value and an adjusted mud cake parameter value using the estimated mud cake parameter value; and to provide corrected galvanic tool resistivity measurements based on at least the adjusted mud cake parameter value. Additional apparatus, systems, and methods are disclosed.

Abstract: A downhole tool, comprising: a tool mandrel; a pad comprising a transmitter operable to transmit an electric current into a formation and a receiver operable to receive at least a portion of the electric current from transmitter; an extension from the tool mandrel that couples pad to tool mandrel; and a signal filter positioned in the downhole tool to suppress passage of mandrel leakage current that passes through tool mandrel to pad. A method of resistivity imaging, comprising: disposing a downhole tool into borehole; transmitting a current into formation surrounding the borehole with a transmitter that is extended from tool mandrel of the downhole tool towards borehole wall; and recording at least a portion of the current that returns to receiver of downhole tool, wherein a signal filter suppress passages of mandrel leakage current that passes through the tool mandrel to a pad on which the transmitter is disposed.

Abstract: A system for locating water floods, in some embodiments, comprises: multiple transducers for coupling to a borehole casing to inject current into a formation within which the casing is disposed; and multiple electrodes, each of the electrodes coupled to a different one of the multiple transducers when coupled to the casing, wherein each of the multiple transducers is used to determine a potential between the casing and a corresponding one of the multiple electrodes to which the transducer is coupled, wherein the potentials from the multiple transducers are used to determine a water flood location.

Abstract: A system includes a drillstring in a first borehole. The drillstring includes a magnet rotatable about an axis of the drillstring. The system further includes at least one fiber optic sensor deployed in a second borehole for generating electromagnetic (EM) field measurements in response to a magnetic field produced by rotation of the magnet about the axis of the drillstring. The system further includes a processor in electronic communication with the at least one fiber optic sensor to determine a distance or direction of the magnet relative to the at least one fiber optic sensor based on the EM field measurements.

Abstract: A look-ahead logging method includes obtaining an initial resistivity log. The method further includes deriving an initial formation model based on the initial resistivity log. The method further includes estimating deep resistivity measurements from the initial formation model and deriving a reduced-complexity formation model from the estimated deep resistivity measurements. The method further includes collecting actual resistivity measurements and inverting the actual resistivity measurements, using the reduced-complexity formation model, to obtain look-ahead or look-around parameter values. The method further includes displaying the look-ahead or look-around parameter values or storing the look-ahead or look-around parameter values on a non-transient information storage medium.

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 drilling system includes a roller cone drill bit having a roller cone and at least one antenna loop disposed in the roller cone for detecting magnetic or electromagnetic waves indicative of a target, a resistivity, or a boundary of the subterranean formation, man-made structure, or object. The drilling system may utilize the antenna loop to determine resistivity measurements of a subterranean formation through which the drill bit is being drilled. The location of the antenna in the roller cone may enable increased look-ahead and look-around measurements. In addition, the location of the antenna in the roller cone may facilitate anisotropic resistivity measurements to aid in steering the drill string into a desired portion of the subterranean formation.

Abstract: A system and method of correcting induction logging data for relative dip, wherein an induction logging tool is utilized to collect initial induction logging data at a plurality of frequencies. The initial induction logging data is then corrected for skin effect and borehole effect, after which, inversion is performed on the processed induction logging data to determine a dip effect correction. The dip effect correction is then applied to the initial induction logging data in order to yield induction logging data that is dip corrected to reflect a zero relative dip. Once dip corrected, the induction logging data can be used with resistivity methodologies generally designed for instances where no dip is present in the formation under analysis. In certain embodiments, the inversion step utilizes an additive correction for the dip effect correction.

Abstract: A through-casing formation monitoring system may include a casing string positioned within a wellbore, a power source electrically coupled to a first transmitter configured to produce a magnetic field, a magnetic induction sensor positioned within the casing string such that the magnetic induction sensor allows a continued operation of the wellbore, a fiber optic cable coupled to an electro-optical transducer within the magnetic induction sensor, and an optical interrogation system configured to receive measurements from the magnetic induction sensor via the fiber optic cable.

Abstract: A downhole drilling system may include a pulse-generating circuit; a drill bit including a first and second electrode electrically coupled to the pulse generating circuit to receive an electrical pulse from the pulse-generating circuit and to form an electrical arc between the first and second electrodes during a pulsed drilling operation in a first wellbore; a sensor to record responses to a magnetic field generated by a current in a second wellbore, the current generated by the electrical arc; and a sensor analysis system communicatively coupled to the sensor, the sensor analysis system configured to obtain a measurement from the sensor, the measurement representing the recorded response to the magnetic field and determine a distance between the drill bit and the second wellbore based on the measurement.