Abstract: Downhole tools and techniques acquire information regarding nearby conductors such as pipes, well casing, and conductive formations. At least some method embodiments provide a current flow along a drill string in a borehole. The current flow disperses into the surrounding formation and causes a secondary current flow in the nearby conductor. The magnetic field from the secondary current flow can be detected using one or more azimuthally-sensitive antennas. Direction and distance estimates may be obtainable from the azimuthally-sensitive measurements, and can be used as the basis for steering the drillstring relative to the distant conductor. Possible techniques for providing current flow in the drillstring include imposing a voltage across an insulated gap or using a toroid around the drillstring to induce the current flow.

Abstract: A modular resistivity sensor disposable in a drillstring having a drill bit on a distal end for drilling a wellbore in a formation, includes a sensor body having a longitudinal axis radially offset from a longitudinal axis of the drillstring, one or more transmitting coil antennas disposed along a length of the sensor body, one or more receiving coil antennas disposed along a length of the sensor body, and a calibrating device configured to calibrate signals generated from the receiving coil antennas.

Abstract: A method for water monitoring about a deviated well is disclosed. The method includes positioning a series of electromagnetic (EM) receivers in a completed deviated wellbore, said receivers being spaced along substantially the length of the well located in a region of a reservoir to be monitored. The method also includes positioning an electromagnetic (EM) source at a first Earth surface location. Then the EM source is activated for a first survey measurement of the reservoir, and an EM field detected at each EM receiver is recorded. The EM source is moved to a second Earth surface location, and activated for a second survey measurement of the reservoir, and an EM field detected at each EM receiver is recorded. From the first and second survey measurements at each of the receivers, an inversion is performed to determine position of water about (and specifically below) the horizontal well.

Abstract: The invention is concerned with a tool and method for determining a downhole parameter. The tool is located in mud surrounded by a formation and comprising a first electrode spaced at a distance from the formation for measuring a first impedance. There is a second electrode located at a second distance from the formation for measuring a second impedance. There is a processing unit for measuring a difference between the first impedance and the second impedance and wherein the parameter is determined based on the difference.

Abstract: The invention is concerned with a tool and method for imaging a formation through a substantially non-conductive medium. The tool comprises first circuitry for injecting a current into the formation, wherein a complex impedance to the current is measured. Second circuitry for determining a phase angle of an impedance of the non-conductive medium and third circuitry for determining a component of the complex impedance that is orthogonal to the phase angle.

Abstract: Cross-well electromagnetic (EM) imaging is performed using high-power pulsed magnetic field sources, time-domain signal acquisition, low-noise magnetic field sensors, spatial oversampling and super-resolution image enhancement and injected contrast fluids. The contrast fluids increase the electromagnetic character of the formation and fluids, either the magnetic permeability or the dielectric permittivity. The acquired signals are processed and inter-well images are generated mapping electromagnetic (EM) signal speed (group velocity) rather than conductivity maps. EM velocity maps with improved resolution for both native and injected fluids are provided.

Abstract: A method for determining the frequency-dependent dielectric permittivity spectrum of a rock sample, comprising:—defining a series of electromagnetic measurement data comprising at least a first measurement at a frequency from which a substantially frequency-independent value of dielectric permittivity ??, can be obtained; and at least second and third measurements at different frequencies from which values for frequency-dependent dielectric permittivity ?rock (f) can be obtained; and—using the first, second and third measurements to determine the frequency-dependent spectrum of the sample.

Abstract: A drill string can include at least one transmit antenna and at least one receive antenna. The transmit antenna transmits at least one electromagnetic signal into a region of an earth formation. The receive antenna receives the signal from the region of the earth formation. The transmit antenna comprises one of a magnetic dipole and an electric dipole, and the receive antenna comprises the other of the magnetic dipole and the electric dipole. At least one characteristic of the region of the earth formation is determined, based at least partially on a first signal as received by the receive antenna at a first time, a second signal as received by the receive antenna at a second time, and a distance traveled by the drill string between the first and the second times. A homogeneous part of the electromagnetic signal may be reduced, to thereby increase a depth of detection of the characteristic.

Abstract: A formation core analysis system can include an inner barrel and a toroidal electromagnetic antenna which transmits electromagnetic signals into a formation core when the core is received in the inner barrel. Another formation core analysis system can include an inner barrel and multiple longitudinally spaced apart electrodes which electrically contact a formation core when the core is received in the inner barrel. A speed of displacement of the core into the inner barrel may be indicated by differences between measurements taken via the electrodes as the core displaces into the inner barrel. A method of measuring resistivity of a formation core as the core is being cut can include transmitting electromagnetic signals into the core from a toroidal electromagnetic antenna as the core is being cut by a coring bit.

Abstract: The present disclosure describes various antenna assemblies, each antenna coil being disposed about a tool body section in an antenna pathway. The antenna pathway passes through alternating grooves and lands. In each embodiment, at least one of the grooves is disposed in the tool body section at a non-axial direction relative to the longitudinal axis of the tool body section. In an embodiment, the antenna coil is an axial coil or a tilted coil. Additional grooves oriented at axial direction may be disposed on the tool body section. Each of the antenna assemblies disclosed may be employed in an electromagnetic logging tool for providing directional measurements while drilling.

Abstract: An apparatus for estimating a property of an earth formation penetrated by a borehole, apparatus including: a carrier configured to be conveyed through the borehole; a transducer disposed at the carrier and configured to transmit and/or receive electromagnetic energy into and/or from the earth formation to estimate the property; wherein the transducer includes a plurality of inductively coupled elements in a series, each element configured to transmit and/or receive electromagnetic energy and at least a first connection to a first element in the plurality and a second connection to a second element in the plurality with at least one of the first element and the second element being disposed between end transducer elements in the series.

Abstract: Various techniques for generating a polar display include a method, which involves receiving information identifying a formation property of an anomaly within a geologic formation from a measurement-while-drilling (MWD) tool that includes several sensors. The formation property is identified by at least one magnitude and at least one distance. The formation property is also identified relative to a corresponding property of the geologic formation. The method also involves receiving information identifying an azimuthal angle from the MWD tool, where the azimuthal angle relates a position of the anomalous formation to a position of a first sensor. The method then generates a graphic, based upon the at least one magnitude and the at least one distance and the azimuthal angle, and displays the graphic on a polar display, in which a center of the polar display corresponds to a location of the borehole in which the MWD tool is located.

Abstract: A method for performing detection of a bed boundary can include deploying a tool body with a longitudinal axis in a borehole, modulating the magnetic moments of electromagnetic signals to be transmitted by the first transmitter and the second transmitter, firing the first transmitter and the second transmitter substantially simultaneously, utilizing the receiver to receive and measure the modulated electromagnetic signals from the first transmitter and the second transmitter, and computing the orientation and location of the bed boundary based on the amplitudes and phases of the electromagnetic signals received and measured at the receiver. The tool body can be deployed with a first transmitter, a second transmitter, and a receiver, all of which are oriented in different directions. The vector of the total magnetic moment of the modulated electromagnetic signals can electrically rotate during firing. A corresponding apparatus for detection of a bed boundary is also provided.

Abstract: An apparatus for making directional resistivity measurements of a subterranean formation includes a resistivity tool with a longitudinal axis and an outer surface, multiple slots formed on the outer surface of the resistivity tool and oriented substantially parallel to the longitude axis of the resistivity tool, and multiple wires posited in the slots and electrically connecting end walls of the slots to form magnetic dipole antennas. The mantic dipole antennas form at least one transmitter-receiver antenna group to perform transmission and reception of electromagnetic signals. A corresponding method for making directional resistivity measurements is also provided.

Abstract: An apparatus for estimating a property of an earth formation penetrated by a borehole, the apparatus having: a carrier configured to be conveyed through the borehole; a transmitter disposed at the carrier and configured to transmit electromagnetic energy at a first frequency into the formation; a first antenna disposed at the carrier and configured to receive electromagnetic signals from the formation as a result of the transmitted electromagnetic energy interacting with the formation; and an active filter coupled to the antenna and configured to filter electromagnetic signals received by the antenna to let the electromagnetic signals at the first frequency pass for processing to estimate the property.

Abstract: Methods and related systems are described for making an electromagnetic induction survey of a formation surrounding a cased section of a borehole. An electromagnetic transmitter and/or receiver is deployed into the cased section of the borehole. Electromagnetic survey measurements and impedance measurements relating to impedance of the transmitter and/or receiver are made while deployed in the section of the borehole. Compensation is made for the attenuation amplitude and/or phase in the electromagnetic survey measurements due to the conductive casing. The compensation is based on the impedance measurements and equivalent circuit parameters. The impedance measurements are correlated with numerical modeling results of a purely inductive electromagnetic transducer, and calculated equivalent circuit parameters are combined with the numerical modeling results.

Abstract: A system for use in downhole detection comprises a downhole arrangement defining a throughbore and a tool deployable through the throughbore of the downhole arrangement. The system further comprises a primary electromagnetic element provided on one of the downhole arrangement and the deployable tool and a secondary electromagnetic element provided on the other of the downhole arrangement and the deployable tool, wherein the primary and secondary electromagnetic elements are configurable for electromagnetic coupling therebetween. Such a system may be used for determining a status and/or an identity of a downhole tool in an oil or gas well from a determined degree of electromagnetic coupling between the primary and secondary electromagnetic elements.

Abstract: A method and apparatus is provided for collecting reservoir data. The method includes providing one or more electromagnetic sources for generating an electromagnetic field in a reservoir and providing one or more electromagnetic sensors equipped with capacitive electrodes. The electromagnetic source is located separately from the electromagnetic sensor. The electromagnetic sensor may either be located within a well or at the surface, is capable of measuring the electromagnetic field in three dimensions, and may be isolated from the well fluids. The data collected by the electromagnetic sensors can be used to create a model of the oil reservoir, including the water saturation.

Abstract: A multicomponent induction logging tool uses a nonconducting mandrel. A central conducting member including wires that electrically connect at least one of the antennas to another of the antennas. Electrodes disposed about the transmitter antenna form a conductive path through a borehole fluid to the central conducting member.

Abstract: An electromagnetic energy transmitter is provided for induced polarization mapping with a borehole to surface electromagnetic (BSEM) transmitter. The transmitter is lowered into a well borehole to a desired location in a well borehole to emit electromagnetic energy. An array of receivers spaced over an area of the earth surface senses the induced polarization response to the emitted electromagnetic energy in areas of interest for mapping. Maps are formed of the induced polarization responses sensed by the array of receivers.

Abstract: An electromagnetic energy transmitter is provided for induced polarization logging with a borehole to surface electromagnetic (BSEM) transmitter. The transmitter is lowered into a well borehole to a desired location in a well borehole to emit electromagnetic energy for the surveys. The transmitter affords more accurate measurements of its position in the well borehole. The transmitter also senses pressure and temperature conditions at its borehole location to provide indications of detected potential problems in the well from the survey or other sources, and to reduce risks and enhance safety and quality of the operations.

Abstract: A logging tool for use in a borehole to obtain multicomponent resistivity induction measurements using collocated coils wherein each of the transverse antennas comprises a pair of mirror-image coils symmetrically disposed about an axis of the logging tool.

Abstract: Disclosed is a method for determining calibration factors of an induction tool that includes three receiver coils, each having a distinct orientation. The method includes: placing the induction logging tool in a first position at a first height above a surface of the earth; performing a first set of measurements of conductivity using the receiver coils with the induction logging tool in the first position at the first height; placing the induction logging tool in a second position at a second height above the surface of the earth; performing a second set of measurements of conductivity using the receiver coils with the induction logging tool in the second position at the second height; and determining the calibration factors that correct conductivity measurements performed by the induction logging tool in a borehole penetrating the earth using the first and second sets of measurements.

Abstract: Techniques related to making resistivity measurements of an underground formation surrounding a borehole involve using a tool having a pad mounted on the body of the tool. The pad has a current injector electrode and a current return electrode mounted on the pad face and arranged such that the current injector and return electrodes are electrically isolated from each other when in use. Two impedance ratios are determined. The first is a ratio of the electrical impedance between the current injector electrode and the tool body, and the electrical impedance between the current return electrode and the tool body. The second is a ratio of the electrical impedance between the current injector electrode and the formation, and the electrical impedance between the current return electrode and the formation. The tool is arranged such that the two impedance ratios differ by 25% or less of the larger impedance ratio.

Abstract: The present disclosure relates to a method to determine a characteristic of a subsurface formation using electromagnetic coupling components. A downhole logging tool having one or more transmitters and one or more receivers, and being capable of measuring the electromagnetic coupling components is provided. The electromagnetic coupling components are measured using the downhole logging tool and used to form a 3-D Lateral Indicator and/or a 3-D Longitudinal Indicator. The 3-D Lateral Indicator and/or the 3-D Longitudinal Indicator are used to determine the characteristic of the subsurface formation.

Abstract: A system and methods for facilitating drilling and/or drilling a well in an orientation with respect to an existing well are provided. Specifically, one method in accordance with present embodiments is directed to producing a magnetic field with a magnetic field source positioned in a non-magnetic region of casing within a first well, wherein the first well is cased with alternating regions of magnetic casing and non-magnetic casing. The method may also include producing at least one output from at least one magnetic field sensor capable of sensing directional magnetic field components, wherein the at least one output is based on detection of the magnetic field and wherein the at least one magnetic field sensor is positioned in a second well.

Abstract: Methods and apparatus for detecting nearby conductors such as pipes, well casing, etc., from within a borehole. A nearby casing string can be detected by transmitting an electromagnetic signal from a first antenna on a downhole logging tool and measuring a response signal with a second antenna. As the tool rotates, the transmitting and measuring are repeated to determine the azimuthal dependence of the response signal. The azimuthal dependence is analyzed to determine an diagonal component and a cross component. The amplitude of the diagonal component is indicative of distance to the conductive feature. Direction can be determined based on the diagonal component alone or in combination with the cross component. Sinusoidal curve fitting can be employed to improve accuracy of the distance and direction estimates. At least one of the antennas is preferably tilted. Measurement results are presented for parallel tilted and perpendicular tilted antennas.

Abstract: A system and a method for time lapse monitoring of a target feature within a rock formation are provided. The system includes a data weighted electromagnetic source configured to generate an electromagnetic field in vicinity or at a surface of the rock formation; and an electromagnetic receiver configured to measure a component of the electromagnetic field generated by the source. The data weighted electromagnetic source includes a plurality of electromagnetic sources and an electromagnetic field contribution from each electromagnetic source is weighted so as to enhance the component of the electromagnetic field measured by the electromagnetic receiver.

Abstract: An apparatus for determining the resistivity of formation surrounding a borehole comprising: an elongate conductive body; a pair of transmitter antennas comprising first and second antennas mounted on the body for inducing a current in the formation; and a pair of receiver antennas comprising first and second antennas mounted on the body for measuring an axial current running in the tool body at the location of the receivers; wherein the pair of transmitter antennas is located to one side of the pair of receiver antennas.

Abstract: A technique utilizes the acquisition of data from desired subterranean regions via a logging system. The logging system is constructed for use in a wellbore and comprises a transmitter module having a transmitter antenna. Additionally, the logging system utilizes a receiver module spaced from the transmitter module and having a receiver antenna. The transmitter antenna and the receiver antenna are oriented to enable sensitivity in desired directions, such as ahead of the logging system.

Abstract: An apparatus for utilizing a pre-existing telemetry transmitter near a drill bit for transmitting or receiving signals to make measurements of surrounding formation resistivity includes a drill collar, at least two toroidal receiving antennas deployed on the drill collar and spaced at an axial distance from each other for receiving or transmitting signals from or to the telemetry transmitter, at least two receiver modules coupled to the toroidal receiving antennas for processing signals received or to be transmitted from or to the telemetry transmitter and adjusting frequency the receiver modules work at, and a converting module coupled to the receiver modules. The converting module includes a microprocessor for calculating the surrounding formation resistivity and controlling the frequency tuners in the receiver modules.

Abstract: A method, a system, and an apparatus are described for the data acquisition in the well-logging of a borehole wall during the investigation of formation properties. Data acquisition is conducted by either an adaptive phase compensation processing or a modulus mode processing, both of which use in-phase and out-of-phase current components to obtain current values. Adaptive phase compensation employs a calculation of a phase shift compensation value, which may then be applied to subsequent acquisitions and can be further processed in the generation of an image of the borehole wall.

Abstract: Methods and related systems are described for making an electromagnetic induction survey of a formation surrounding a cased section of a borehole. An electromagnetic transmitter and/or receiver are deployed into the cased section of the borehole. One or more additional devices are used to measure the properties of a conductive casing relating to conductivity, thickness and magnetic permeability. A casing coefficient is then calculated that can then be used for the processing of the deep-sensing induction measurements.

Abstract: An electromagnetic method for obtaining a dip azimuth angle from downhole electromagnetic measurements includes acquiring electromagnetic measurement data in a subterranean borehole from at least one measurement array. The electromagnetic measurement data is processed by a least squares method to obtain the dip azimuth angle. Related systems and apparatuses are also disclosed herein.

Abstract: Fiberoptics can be employed to detect downhole electromagnetic signals via resistive heating. A disclosed electromagnetic energy detector embodiment includes an optically-interrogated temperature sensor; and a conductive element thermally coupled to the sensor, the conductive element having a temperature response to incident electromagnetic energy. The optically-interrogated temperature sensor may be a length or coil of optical fiber to which a distributed acoustic sensing (DAS) or distributed temperature sensing (DTS) system is attached. The conductive element may be a metal coating on the fiber that experiences resistive heating in response to electromagnetic energy and creates an optically-measurable thermal response in the sensor.

Abstract: Location determination is performed using a transmitter including an elongated generally planar loop antenna defining an elongation axis. The elongation axis is positioned along at least a portion of a path. A magnetic field is then generated which approximates a dipole field. Certain characteristics of the magnetic field are then determined at a receiving position radially displaced from the antenna elongation axis. Using the determined certain characteristics, at least one orientation parameter is established which characterizes a positional relationship between the receiving position and the antenna on the path. The magnetic field may be transmitted as a monotone single phase signal. The orientation parameter may be a radial offset and/or an angular orientation between the receiving position and the antenna on the path. The antenna of the transmitter may be inserted into a first borehole to transmit the magnetic field to a receiver inserted into a second borehole.

Abstract: An electromagnetic energy transmitter is provided for borehole to surface electromagnetic (BSEM) surveying. The transmitter is lowered into a well borehole to a desired location in a well borehole to emit electromagnetic energy for the surveys. The transmitter affords more accurate measurements of its position in the well borehole. The transmitter also senses pressure and temperature conditions at its borehole location to provide indications of detected potential problems in the well from the survey or other sources, and to reduce risks and enhance safety and quality of the operations.

Abstract: An apparatus and related methods are described for detecting features of a reservoir surrounding a borehole, the apparatus being capable of emitting an electromagnetic wave signal and receiving a signal representing a response of the reservoir to the electromagnetic wave signal, wherein the emitted signal is a broadband signal selected from within the range of 1 Hz to 1000 Ghz and the received signal includes a directional characteristic to provide an azimuthal determination of the direction of a discontinuity within the formation as the discontinuity reflects or scatters at least part of the broadband signal; azimuthally scanning the surrounding formation; and inverting the received signal for deriving at least a distance of the reflecting discontinuity from the borehole using simultaneous inversion of the reflected or scattered wavefield at multiple frequencies.

Abstract: An apparatus and method for estimating a parameter of interest of an earth formation. An apparatus includes an elongated support member; a primary transmitter on the elongated support member; and a receiver toroid on the elongated support member, the receiver toroid being positioned transversely on the elongated support member and including a single coil antenna. Methods include positioning a logging tool in a borehole in the earth formation; using a transverse receiver toroid on an elongated support member on the logging tool, wherein the transverse receiver toroid includes a single coil antenna; and producing a signal responsive to an electrical signal produced by a primary transmitter.

Abstract: An antenna (3) of an electromagnetic probe used in investigation of geological formations GF surrounding a borehole WBH comprises a conductive base (31) and an antenna element (32). The conductive base (31) comprises an opened non-resonant cavity (33). The antenna element (32) is embedded in the cavity (33) and goes right through the cavity. The antenna element (32) is isolated from the conductive base (31). The antenna element (32) is coupled to at least one electronic module via a first 34A and a second 34B port, respectively. The electronic module operates the antenna so as to define a simultaneously superposed pure magnetic dipole and pure electric dipole.

Abstract: A dipole antenna may be created by surrounding a portion of the continuous conductor with a nonconductive magnetic bead, and then applying a power source to the continuous conductor across the nonconductive magnetic bead. The nonconductive magnetic bead creates a driving discontinuity without requiring a break or gap in the conductor. The power source may be connected or applied to the continuous conductor using a variety of preferably shielded configurations, including a coaxial or twin-axial inset or offset feed, a triaxial inset feed, or a diaxial offset feed. A second nonconductive magnetic bead may be positioned to surround a second portion of the continuous conductor to effectively create two nearly equal length dipole antenna sections on either side of the first nonconductive magnetic bead. The nonconductive magnetic beads may be comprised of various nonconductive magnetic materials, and preformed for installation around the conductor, or injected around the conductor in subsurface applications.

Abstract: A detection system of geological formations, particularly but not exclusively used for oil exploration, and for characterization and monitoring of hydrocarbon reservoirs. The detection system includes an electromagnetic transmission device positioned on a surface of a geological formation close to a first well having a vertical development direction, the first well being covered by a metal casing, and an electromagnetic reception device positioned deep inside the first well, the electromagnetic reception device including an electromagnetic detector. The electromagnetic transmission device includes a primary electromagnetic field generator configured to generate a primary electromagnetic field focalized in a direction of the metal casing, the metal casing irradiating the primary electromagnetic field into the geological formation.

Abstract: A method and system for calculating formation porosity is presented. The method includes calculating formation porosity of a borehole by obtaining complex dielectric constant measurements with a high frequency dielectric tool. Next, a dielectric constant of formation water is derived from the complex dielectric constant measurements. Finally, a formation porosity is determined based at least in part on the measured complex dielectric constant and the derived dielectric constant formation water.

Abstract: A method for determining spatial distribution of fluid injected into a subsurface rock formation includes injecting the fluid into the rock formation. The fluid includes therein electrically conductive solid particles dispersed in an electrolyte. An electromagnetic response of the formation is measured. The measured electromagnetic response is used to determine spatial distribution of the injected fluid.

Abstract: A method of determining anisotropy in a borehole is disclosed. An array of measurements along the borehole is obtained and a first depth in the borehole is selected. An arbitrary plane oriented with respect to the borehole at the first depth is designated and an anisotropy for the first depth with respect to the arbitrary plane is determined. The arbitrary plane is repositioned at the first depth and an anisotropy for different positions of the arbitrary plane at the first depth is determined. A minimum anisotropy coefficient with respect to the arbitrary plane at the first depth is identified based on anisotropy for different positions of the arbitrary plane. An anisotropy tensor for the first depth is then identified.

Abstract: A method and system to predict dielectric behavior in a wide frequency range in a wellbore. The method comprising: deploying a tool in a wellbore, measuring the permittivity and conductivity at more than one frequency of a formation with the tool, and predicting the dielectric behavior of saline water in a wide band frequency range and temperature.

Abstract: A method for reconstructing a borehole image includes determining a spatial sensitivity function for a borehole imaging tool and using the imaging tool to obtain a borehole image of a subterranean formation. A reconstructed image is then computed from the borehole image and the spatial sensitivity function.

Abstract: Logging tools and methods employing an at-bit loop antenna to acquire azimuthal resistivity measurements proximate to the bit enable low-latency geosteering signals to be generated. In some embodiments, the at-bit antenna is part of a bottom hole assembly that includes a drill bit, a mud motor, and a resistivity tool. The mud motor is positioned between the at-bit antenna and the resistivity tool. The resistivity tool includes at least one loop antenna that is not parallel to the at-bit loop antenna. The at-bit antenna is part of an at-bit module that, in some embodiments, transmits periodic electromagnetic signal pulses for the resistivity tool to measure. In other embodiments, the at-bit module measures characteristics of electromagnetic signal pulses sent by the resistivity tool and communicates the measured characteristics to the resistivity tool via a short hop telemetry link.

Abstract: A system, method and device for interrogating a downhole environment in a borehole beneath a surface includes a source of electromagnetic energy operable to transmit an electromagnetic signal in the borehole, a sensor module, including a passive resonating circuit including a crystal oscillator having a resonant frequency that varies with changes in the condition in the downhole environment in response to a condition in the downhole environment in the borehole and a detector positionable to receive the reflected modulated electromagnetic signal. In an embodiment, a solids-free dielectric medium is provided within an annular volume in the borehole defined by the casing through which the electromagnetic signal is transmitted.

Abstract: To analyze content of a subterranean structure, electric field measurements at plural source-receiver azimuths in a predefined range are received. Total magnetic field measurements are also received at plural source-receiver azimuths in the predefined range. The electric field measurements and the total magnetic field measurements are provided to an analysis module to enable determination of electrical resistivity anisotropy of the subterranean structure.