Abstract: A system and method of evaluating a subterranean earth formation using a statistical distribution of formation data. The system comprises a logging tool and a processor in communication with the logging tool. The logging tool comprises a sensor operable to measure formation data and is locatable in a wellbore intersecting the subterranean earth formation. The processor is operable to calculate inversion solutions to the formation data, wherein each inversion solution comprises values for a parameter of the formation, and generate a statistical distribution of the parameter along one or more depths in the subterranean earth formation using the inversion solutions. The processor is also operable to identify peaks within the statistical distribution and select the inversion solutions corresponding to the identified peaks, generate a formation model using the selected inversion solutions; and evaluate the formation using the formation model to identify formation layers for producing a formation fluid.

Abstract: Disclosed embodiments include apparatus, systems, and methods which operate to include monitoring an electromagnetic signal and/or gamma ray spectra count values to determine interception of a first well created by a drill string, with a well casing surrounding a second well. Interception can be determined when a reception antenna is used to receive the electromagnetic signal, by examining values associated with the magnitude of the signal. Interception can also be determined when a ratio of the gamma ray spectra count values have exceeded a first predetermined threshold, or when capture gamma energy indicated by the gamma ray spectra count values exceeds a second predetermined threshold. Additional apparatus, systems, and methods are disclosed.

Abstract: A method for synchronizing signals among transmitters and receivers of a logging tool positioned in a borehole is provided. Measurement signals generated from operating a transmitter in the borehole are acquired by a receiver. An operating frequency of the receiver is determined by a processing unit. The operating frequency of the receiver is different from an operating frequency of the transmitter. A sampling frequency of the receiver is determined based on the determined operating frequency. A phase delay of the receiver is determined by the processing unit. The acquired measurement signals are adjusted by the processing unit based on the determined sampling frequency and the phase delay of the receiver.

Abstract: In accordance with presently disclosed embodiments, a system and method for determining a measurement for a pseudo receiver antenna with a different lateral position and a different azimuthal direction than at least two receiver antennas disposed on one or more wellbore tools is provided. The method involves transmitting an electromagnetic signal into a subterranean formation surrounding a borehole, and measuring one or more responses of the subterranean formation to the electromagnetic signal using at least two receiver antennas. The two receiver antennas are oriented in differing azimuthal directions relative to one or more tools to which the receiver are coupled, and arranged in a non-parallel angular orientation with respect to each other. The method then includes determining a response measured by a pseudo receiver antenna with a desired angular orientation and a desired azimuthal direction with respect to the one or more tools.

Abstract: A pixelation-based approach to summarize downhole inversion results acquires inversion solutions and generates an initial model. Each layered solution is pixelated into pixels where each pixel contains the resistivity value of the initial model. A weighted function that weighs pixels according to their proximity to the logging tool may be used to generate the pixelated model to thereby improve accuracy. A statistical summary study is performed to identify the best pixelated model, which is then used to determine one or more formation characteristics.

Abstract: An antenna assembly includes a tool mandrel having a tool axis and a coil including a plurality of windings wrapped about the tool mandrel at a winding angle offset from the tool axis. An antenna shield is secured to the tool mandrel and positioned radially outward from the coil. The antenna shield defines a plurality of slots extending perpendicular to the coil at any angular location about a circumference of the tool mandrel and the plurality of slots is provided in two or more dissimilar lengths.

Abstract: In accordance with presently disclosed embodiments, a system and method for determining a measurement for a pseudo receiver antenna with a different lateral position and a different azimuthal direction than at least two receiver antennas disposed on one or more wellbore tools is provided. The method involves transmitting an electromagnetic signal into a subterranean formation surrounding a borehole, and measuring one or more responses of the subterranean formation to the electromagnetic signal using at least two receiver antennas. The two receiver antennas are oriented in differing azimuthal directions relative to one or more tools to which the receiver are coupled, and arranged in a non-parallel angular orientation with respect to each other. The method then includes determining a response measured by a pseudo receiver antenna with a desired angular orientation and a desired azimuthal direction with respect to the one or more tools.

Abstract: A logging tool and a method for in-situ, independent calibration of receiver amplifier electronics separately from transmitter electronics. A logging tool can perform in-situ gain and phase calibration on one or more receiver assemblies, each consisting of at least a receiver amplifier electronics and a receiver antenna, and based on a calculated gain and phase of the receiver assembly, determine the true antenna amplitude and phase associated with a measurement made by the receiver assembly. The logging tool can perform in-situ crosstalk measurement and calibration, by determining a crosstalk matrix for all of the receiver assemblies and for each receiver assembly, removing the crosstalk interference from the measurement made by the receiver assembly.

Abstract: Methods to accurately plan and optimize clamped source excitation in ranging or telemetry operations approximate a well having a complex pipe structure as a simple solid pipe (“effective model”) with an effective pipe cross-section and resistance. The simple solid pipe is then treated as a thin wire and analyzed using a FAST Code.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to determine spatial orientations of one or more transmitters attached to a first downhole component, relative to one or more receivers attached to a second downhole component, at common points in time during rotation of the first and the second downhole components. The first downhole component may be variably, rotationally coupled to the second downhole component. Further activity may include transforming raw measurements of transmitter signals provided by the receiver(s) into calibrated measurements based on the spatial orientations at the common points in time. Additional apparatus, systems, and methods are described.

Abstract: An apparatus includes a down hole tool housing attached to a ranging electromagnetic field strength sensor. The ranging electromagnetic field strength sensor is to measure electromagnetic field strength components associated with an electromagnetic field originating at a first well, via at least one of direct transmission and backscatter transmission, when the down hole tool housing is disposed in a second well, to provide ranging measurements to calculate an approximate range between the first well and the second well. The apparatus includes a reference electromagnetic field strength sensor to provide a closed loop current path around the down hole tool housing, to provide distorting field strength measurements.

Abstract: An antenna assembly includes a tool mandrel having a tool axis, and a coil including a plurality of windings wrapped about the tool mandrel at a winding angle offset from the tool axis. A soft magnetic band radially interposes the coil and the tool mandrel and extends about a circumference of the tool mandrel at a band angle parallel to the winding angle. The soft magnetic band includes a plurality of stacked inserts extending perpendicular to the coil about the circumference of the tool mandrel and each stacked insert includes a plurality of rods positioned end-to-end.

Abstract: Methods and systems are presented in this disclosure for estimation of formation properties and pipe properties using ranging measurements. Embodiments of the present disclosure utilize ranging measurements to first determine a defined slope (e.g., leakage rate) of an electrical current signal flowing along a wellbore. The determined slope (e.g., leakage rate) may be then used to estimate properties of a formation surrounding the wellbore (e.g., formation resistivity) and properties of a conductive material (casing pipe) deployed in the wellbore (e.g., pipe resistance). Based on the estimated properties of the formation and the conductive material, drilling operation in a drilling well can be adjusted, and repair of defects or mechanical deformations on the casing pipe can be initiated.

Abstract: Apparatus, systems, and methods for ranging operate to use a wireline active ranging system to initially determine a relative distance and relative direction from a first well (e.g., ranging well) to a second well (e.g., target well) and an EM azimuthal logging tool to maintain or adjust the distance from the target well while drilling the ranging well. Additional apparatus, systems, and methods are disclosed.

Abstract: Disclosed herein are electromagnetic logging systems and methods that provide a set of signals that robustly approximate the response of a model tool employing orthogonal triads of point-dipole antennas. One illustrative method embodiment obtains an azimuthally sensitive electromagnetic logging tool's signal measurements as a function of position in a borehole, the tool having at least two spacing distances (d1, d2) between transmit and receive antennas. Orthogonal direct coupling measurements (Vxx, Vyy, Vzz) are derived from the signal measurements and converted into a set of robust signals, the set including: a ratio between Vzz coupling components at different spacing distances, a ratio between Vxx and Vzz coupling components, a ratio between Vyy and Vzz coupling components, and a ratio between Vxx and Vyy coupling components. The set may include an additional robust signal having a ratio between a sum of cross-coupling components Vxz+Vzx or Vyz+Vzy and a sum of orthogonal direct coupling components.

Abstract: Methods to accurately plan and optimize clamped source excitation in ranging or telemetry operations approximate a well having a complex pipe structure as a simple solid pipe (“effective model”) with an effective pipe cross-section and resistance. The simple solid pipe is then treated as a thin wire and analyzed using a FAST Code.

Abstract: Signal measurements collected by azimuthally sensitive electromagnetic logging tool as a function of position in a borehole are obtained. The signal measurements are used to identify a type of formation model. An inversion technique appropriate to the type of formation model is applied to the set of signal measurements to determine a geophysical property. The geophysical property is used to make a decision regarding drilling a well.

Abstract: A method for calibrating a gradiometer tool, method for ranging, calibrated gradiometer tool, and ranging system are disclosed. A gradiometer tool may be included along a drilling string and have at least one magnetic field sensor, a processor, and a memory storing a recovery matrix obtained by modeling a set of magnetic field values extent at the at least one sensor over the range of tool face angles due to a known current flowing through a current loop of known finite dimensions at a known distance with respect to the gradiometer tool and calculating at least one effective distance corresponding to at least one of the set of magnetic field values that would arise if the gradiometer tool is placed to a theoretical infinite line source carrying the current at the effective distance.

Abstract: Methods and tools for detecting casing position downhole is presented. The method utilizes electromagnetic (EM) tools with tilted antenna systems to detect casing position. Sometimes titled antenna designs also increase EM tools' sensitivity to formation parameters, which can lead to false signals for casing detection. In addition, it is very difficult to distinguish measured signals between a casing source and a formation source. The methods presented help to distinguish between the two sources more clearly. The methods and tools presented also help to minimize those environmental effects, as well as enhance the signals from a surrounding conductive casing. The methods herein provide ideas of EM tool's design to precisely determine casing position within a certain distance to casing position.

Abstract: Various embodiments include apparatus and methods to determine true formation resistivity. Such apparatus and methods may use techniques to effectively reduce or eliminate polarization horn effects at boundaries between formations of different resistivity. The techniques may use combinations of geosignals and adjustments of measurement data to evaluate true formation resistivity for formation layers investigated. Such techniques and associated analysis may be conducted real time. Additional apparatus, systems, and methods are disclosed.