Abstract: Ground penetrating radar (GPR) measurements from a downhole well tool in a wellbore are obtained to identify length of fractures adjacent the wellbore. A ground penetrating radar transmitter of the downhole tool emits an electromagnetic pulse. The electromagnetic wave of the ground penetrating radar is diffracted on encountering an end or tip of a fracture, which acts as a secondary source. The diffracted signal is then collected by downhole receiver(s) of the downhole tool. Length of the fracture is determined based on the time of travel of the electromagnetic wave from its emission until its collection as a diffracted signal by the downhole receiver(s).

Abstract: A method to obtain gain-corrected measurements. A measurement tool having one or more arrays is provided, wherein the arrays include two co-located triaxial transmitters and two co-located triaxial receivers. Measurements are obtained using the transmitters and the receivers. Impedance matrices are formed from the obtained measurements and the impedance matrices are combined to provide gain-corrected measurements. The apparatus may alternatively be a while-drilling logging tool having one or more arrays, wherein each array comprises a transmitter, a receiver, and a buck, and wherein the signal received by the receiver is subtracted from the signal received by the buck or vice versa. A slotted shield may be incorporated into either embodiment of the tool. The slots may form one or more island elements. A material is disposed in the slots. The islands and shield body have complementary tapered sides that confine the islands within the shield body.

Abstract: A logging tool having a plurality of spatially separated antennas is provided and used to make propagation-style measurements in a formation. Tensors are formed using the propagation-style measurements and one or more quantities are computed using the tensors. A formation evaluation is performed using the computed quantities. The formation evaluation determines a formation property or parameter such as horizontal resistivity, vertical resistivity, relative dip, azimuthal dip, bed boundary location, or bed thickness. The computed quantities may include compensated phase shift resistivity, compensated attenuation resistivity, symmetrized phase shift resistivity, symmetrized attenuation resistivity, anti-symmetrized phase shift resistivity, and anti-symmetrized attenuation resistivity. The measurements may be corrected for antenna gain errors and an air calibration may be performed.

Abstract: A resistivity measuring tool used in a drillstring having a drill bit on a distal end for drilling a wellbore in a formation includes a tool body having a longitudinal axis, a pair of transmitter antennas having magnetic moments parallel to the longitudinal axis of the tool body, and a pair of receiver antennas radially spaced from the longitudinal axis of the tool body and having transverse magnetic moment components pointed in opposite directions, wherein at least one of the receiver antennas has a transverse magnetic moment angled with respect to a component normal to the longitudinal axis of the tool body.

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. 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. The antenna coil may be an axial coil or a tilted coil. Additional grooves oriented at axial direction may be disposed on the tool body section. Various methods include acquiring a plurality of data pairs using one or more antenna coils, each data pair comprising an induced signal at a receiver and a corresponding toolface angle using a tool including at least one antenna assembly, to generate a measurement including obtaining information about the directionality of the formation by calculating areas of an induced signal function approximated by the plurality of data pairs.

Abstract: An electromagnetic energy source for emitting pulses of electromagnetic energy includes a sonde assembly having a first section axially aligned with, and spaced from, a second section. An energy storage capacitor includes an electrode mounted in each of the first section and the second section of the sonde assembly and operable to generate an electric field. A capacitive charge storage medium is mounted in each of the first section and the second section of the sonde assembly and surrounds each electrode, where the capacitive charge storage medium is a giant dielectrics and giant permeability ferrite. A fast-closing switch is located between the first and second sections of the sonde assembly.

Abstract: An electromagnetic energy source for emitting pulses of electromagnetic energy includes a sonde assembly and an energy storage capacitor. The energy storage capacitor has an electrode mounted in the sonde assembly and operable to generate an electric field, and a capacitive charge storage medium surrounding the electrode. A communication cable extends through a tubular member to the electrode. A fast-closing switch is positioned such that when the fast-closing switch is in a closed position, a circuit is formed that discharges the electrode.

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 system and method to control drilling based on determining a sensitivity range of an electromagnetic tool include obtaining a resistivity model over an interval of depths, obtaining an original tool response from the resistivity model over the interval of depths for a tool configuration, and positioning an artificial layer in the resistivity model to generate a modified resistivity model. The method also includes obtaining a modified tool response from the modified resistivity model and iteratively performing the positioning the artificial layer and the obtaining the modified tool response, estimating the sensitivity range according to a position of the artificial layer when a normalized difference between the original tool response and the modified tool response reaches a threshold value, and assigning a different confidence level to information obtained from the resistivity model beyond the sensitivity range and controlling the drilling based on the resistivity model and the confidence level.

Abstract: Various embodiments include apparatus and methods to operate a drilling operation relative to formation boundaries. The apparatus and methods can include operating one or more transmitters in a borehole in a formation having a thickness between two boundaries, selecting thickness models based on applying responses from operating the one or more transmitters such that the thickness of the formation is between the two thickness models, and generating a value of a distance to a nearest boundary based on linearization of the thickness models with respect to a long distance investigation parameter and a short distance investigation parameter. Additional apparatus, systems, and methods are disclosed.

Abstract: A method for making downhole electromagnetic logging while drilling measurements includes rotating an electromagnetic logging while drilling tool in a subterranean wellbore. The logging while drilling tool includes at least first and second tilted transmitter antennas longitudinally spaced along a logging while drilling tool body and at least first and second tilted receiver antennas. A plurality of electromagnetic voltage measurements is acquired at the first and second tilted receiver antennas while rotating and processed to compute harmonic voltage coefficient. Ratios of selected ones of the harmonic voltage coefficients are then processed to compute at least one gain compensated measurement quantity.

Abstract: A device which prints an electrically conductive pattern on a downhole tool using electrical ink includes a print head assembly and gripper claw assembly to print and manipulate the downhole tool during printing, respectively. The electrically conductive pattern may be an antenna coil, circuit or other desired pattern. After printing, the accuracy of the pattern is verified by the system and an impact resistant coating is applied to the pattern.

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.

Abstract: Disclosed herein is a method of determining a relation between a resistivity logging tool and casing in an earth formation. The method includes acquiring coupling voltages for different tool face angles, between different antenna components of different axes of a transmitting station transmitting into the earth formation and different antenna components of different axes of a receiving station receiving from the formation, using the resistivity logging tool. Then, spatial Fourier coefficients are extracted from the coupling voltages, using a computing device associated with the resistivity logging tool. The relation between the resistivity logging tool and the casing is then determined as a function of the spatial Fourier coefficients and at least one resistivity measurement of the earth formation, using the computing device.

Abstract: Nuclear magnetic resonance (NMR) logging tools may be configured for situation-dependent NMR logging operations by including two dissimilar coils that may function in four different modes of operation based on logging conditions including: a resistivity of the fluid, a diameter of the wellbore, a depth into the subterranean formation of the volume of investigation, or a combination thereof. For example, an NMR logging tool with a z-coil and a transversal coil may be useful in generating in a volume of investigation of a subterranean formation either (1) a transversal radiofrequency (RF) excitation with the transversal coil or (2) a quadrature RF excitation with both the z-coil and the transversal coil, where the choice of transversal or quadrature RF excitation is based on the logging conditions; and detecting an NMR signal from the subterranean formation with one of: (1) the transversal coil or (2) both the z-coil and the transversal coil.

Abstract: A resistivity measuring tool used in a drillstring having a drill bit on a distal end for drilling a wellbore in a formation includes a tool body having a longitudinal axis, a transmitting antenna, and a receiving antenna. The receiving antenna includes an antenna body having a longer axis disposed longitudinally in the tool body, and a wire coil having a central axis disposed around the antenna body, wherein the wire coil central axis is substantially perpendicular to the longer axis of the antenna body, and wherein the wire coil is configured to generate a magnetic moment orthogonal to the tool body longitudinal axis. The transmitting antenna is configured to transmit electromagnetic energy into the formation and induce a voltage signal related to a parameter of the formation in the receiving antenna.

Abstract: Various triaxial antenna designs having are provided. Some embodiments include a split-z coil that can include two axial coils with saddle coils in the x- and y-directions located therebetween. The split z-coils can function by having a combined magnetic moment similar to that of a single axial coil located between the two parts of the split z-coil. In some examples, the antenna assemblies can include a protrusion or other non-planar structure.

Abstract: Various embodiments include apparatus and methods related to finding a position in an underground formation. Apparatus and methods can include receiving signals from a receiver in an underground formation in response to signals generated from transmitting sources, each of the transmitting sources located at a known position; and processing the received signals, based on the signals generated from the transmitting sources, to determine the position of the receiver. A number of techniques can be applied to processing the received signal. Additional apparatus, systems, and methods are disclosed.

Abstract: A system for determining an orientation of a nitrogen vacancy (NV) diamond material is disclosed. The system includes the NV diamond material having a plurality of NV centers, a magnetic field generator that generates a magnetic field, a radio frequency (RF) excitation source that provides RF excitation, an optical excitation source that provides optical excitation, an optical detector that receives an optical signal emitted by the NV diamond material, and a controller. The controller controls the magnetic field generator to generate a control magnetic field and controls the magnetic field generator to successively generate calibration magnetic fields. The controller successively receives light detection signals from the optical detector, stores measurement values based on the successively received light detection signals, and calculates an orientation of the NV diamond material based on the stored measurement values.

Abstract: An apparatus and method for a property ahead of a drill bit in a borehole penetrating a formation. The apparatus may include at least one receiver toroid disposed on a carrier and a transmitter toroid configured to induce an electromagnetic signal in the formation and disposed between the drill bit and the at least one receiver toroid. The apparatus may include at least one processor configured to estimate the property using a signal produced by the at least one receiver. The method may include estimating the property using the signal produced by the at least one receiver toroid. The method may also include one or more of: (i) generating a conductivity curve based on signals from at least one receiver toroid, (ii) validating signals from one receiver toroid based on a conductivity curve of another receiver toroid, and (iii) filtering a receiver toroid signal using lateral resistivity information.

Abstract: An antenna assembly for wellbore logging tools is provided. The antenna assembly includes a coil wrapped about an outer surface of a bobbin positioned within a saddle of a tool mandrel. The antenna assembly also includes an inner sleeve positioned on an outer surface of the tool mandrel within the saddle, the inner sleeve being interposed between the coil and the tool mandrel. The antenna assembly also includes a plurality of ferrite channels formed within a groove defined in an inner surface of the inner sleeve, in which the plurality of ferrite channels being laterally separated by a plurality of dividers formed in the groove. The antenna assembly also includes a plurality of ferrites disposed within respective ones of the plurality of ferrite channels.

Abstract: Various embodiments include apparatus and methods related to finding a position in an underground formation. Apparatus and methods can include receiving signals from a receiver in an underground formation in response to signals generated from transmitting sources, each of the transmitting sources located at a known position; and processing the received signals, based on the signals generated from the transmitting sources, to determine the position of the receiver. A number of techniques can be applied to processing the received signal. Additional apparatus, systems, and methods are disclosed.

Abstract: Sensor assemblies are described for measuring isotropic, anisotropic, or directionally dependent, characteristics of a subterranean formation. Sensor assemblies can include sensors deployed on a tool string. One or more of the sensors can be rotatable relative to the tool string. Rotating one or more sensors relative to the tool string can provide data about the subterranean formation at multiple points around the tool string.

Abstract: Transient responses of a tri-axial resistivity tool corresponding to an electromagnetic (EM) impulse are derived. A transient response of a directional resistivity tool (DRT) corresponding to the EM impulse is derived based on the transient responses of the tri-axial resistivity tool. A theoretical late time transient response of the DRT is derived based on the transient response of the DRT. The late time transient response of the DRT is measured. An anisotropy, a horizontal conductivity, and a dip angle are determined based on the measured late time transient response and the theoretical late time transient response.

Abstract: A system and method discloses performing a fracture operation at a wellsite about a subterranean formation. The method involves, obtaining wellsite measurements by placing a downhole tool in a wellbore and using the downhole tool to acquire measurements of the subterranean formation, simulating the obtained wellsite measurements to determine formation parameters comprising conductivity tensors based on a formation model of the measured subterranean formation, validating the formation model by comparing the obtained wellsite measurements with the simulated wellsite measurements, generating fracture parameters and triaxiality indicators based on the validated formation model, and fracturing the subterranean formation based on the generated fracture parameters and triaxiality indicators.

Abstract: Data obtained with an electromagnetic energy transmitter in borehole to surface electromagnetic (BSEM) transmitter is processed. The processed data provides measures of detected electromagnetic fields, induced polarization and electromagnetic well logging information of interest for surveying and mapping of subsurface formations.

Abstract: A system comprises one or more electromagnetic coils configured to generate and direct excitation signals toward a plurality of casings in a wellbore and receive response signals based on the excitation signals. The system further comprises one or more processors configured to receive a first response signal from the one or more electromagnetic coils and determine one or more characteristics of a first defect in the plurality of casings using the first response signal and small defect information.

Abstract: Methods and apparatus for determining at least one parameter of interest of an earth formation. Methods include using at least one transmitter to initiate at a single location in the formation a first electromagnetic signal at a first frequency and a second electromagnetic signal at a second frequency different than the first frequency for propagation through the formation; receiving the first electromagnetic signal propagating through the formation and the second electromagnetic signal propagating through the formation at a single receiver non-collocated with the at least one transmitter; estimating a relative phase shift of the second electromagnetic signal relative to the first electromagnetic signal; estimating a relative attenuation of the second electromagnetic signal relative to the first electromagnetic signal; using the relative attenuation and the relative phase shift to estimate a parameter of interest of the formation. The receiver may be unsynchronized with respect to the transmitter.

Abstract: A rotary steerable system includes a non-rotating housing, azimuthal resistivity antennas and electronics, disposed within the non-rotating housing, configured to measure a distance to an approaching upper or lower formation boundary, and a control module configured to steer a drill bit along a well path and, based on measurements from the azimuthal resistivity antennas, to steer the housing away from the approaching upper or lower formation boundary and thereby maintain a certain distance between the steerable housing and upper or lower formation boundary.

Abstract: Systems, methods, and devices for evaluation of an earth formation intersected by a borehole using a logging tool. Methods include exciting an upper and lower transmitter; receiving signals at a plurality of receivers between the upper and lower transmitter; estimating a phase shift attributable to a volume of interest of the formation adjacent to a section of the carrier corresponding to the plurality of receivers by estimating phase shifts attributable only to portions of the volume of interest adjacent to corresponding portions of the section between each adjacent pair of receivers of the plurality of receivers; wherein each adjacent pair is positioned at a corresponding distance that is no more than half of the shortest wavelength of those wavelengths associated with the received signals. Estimating a phase shift between an adjacent pair of receivers may be carried out using a first relative phase value; and a second relative phase value.

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 orthogonal to the winding angle. The soft magnetic band includes a plurality of inserts, and a gap is defined between each laterally adjacent insert and the gap extends parallel to the tool axis.

Abstract: An antenna assembly includes a tool mandrel having a tool axis, and a plurality of coils are collocated about the tool mandrel and each include a plurality of windings wrapped about the tool mandrel. A soft magnetic band radially interposes the plurality of coils and the tool mandrel and includes a plurality of inserts that form two or more annular arrays axially spaced from each other and extend about the tool mandrel at an angle orthogonal to the tool axis. The inserts in each annular array are circumferentially spaced from each other.

Abstract: A method for determining at least one electrical property of an earth formation includes emitting an electromagnetic signal into the earth formation from an antenna and measuring an electromagnetic signal from the earth formation. The antenna is a broadband log antenna mounted on a substrate having at least a high dielectric permittivity, defined as a dielectric permittivity of about ?=100 to ?=1000 or a gigantic dielectric permittivity, defined as a dielectric permittivity of about ?=1000 or greater. The antenna has a radius between about 2.5 millimeters (mm) and 10 centimeters (cm). The method further includes determining at least one electrical property of one or more of a borehole, a borehole fluid, and the earth formation based on measuring the electromagnetic signal.

Abstract: A method may include transmitting a narrowband signal into a formation using a transmitter located in a wellbore. The narrowband signal is modified by passage of through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal having a first frequency. The method also includes sensing the modified narrowband signal with an optical waveguide positioned in the wellbore, transmitting a source signal along a length of the optical waveguide, and obtaining a backscattered return signal from the optical waveguide. The backscattered return signal is sampled at a second frequency that is less than the Nyquist rate of the modified narrowband signal. The method further includes processing the backscattered return signal to obtain an amplitude of the modified narrowband signal.

Abstract: An apparatus for measuring resistivity in a borehole includes first and second modules configured to be conveyed through the borehole and a transmitter connected to the first module, the transmitter transmitting a transmitter signal that causes a field signal to be created in a formation surrounding the borehole. The apparatus also includes a receiver connected to the second module configured to sense the field signal, a reflection generator and a delay determination circuit that includes a pulse generator and a timer. The apparatus also includes a communication link coupling the delay determination circuit and the reflection generator. The delay determination circuit causes a first pulse to be transmitted to the reflection generator and determines an indication that is related to the time until a reflection is received back from the reflection generator.

Abstract: Various embodiments include apparatus and methods of operation with respect to well logging. Apparatus and methods can include a tool having an arrangement of spaced apart transmitter antennas and receiver antennas in transmitter-receiver antenna pairs to make shallow measurements and deep measurements. The signals acquired from the shallow measurements and deep measurements can be processed to provide a look-ahead signal in a drilling operation. The transmitter and receiver antennas can be oriented to cancel or substantially cancel out signals from layers between the transmitter antenna and the receiver antenna in response to the transmitter being operated downhole in a well. Additional apparatus, systems, and methods are disclosed.

Abstract: A method utilized in borehole logging, such as in surveying or exploration relating to a subsurface formation. The method includes deploying a logging instrument that includes a pressure sensor into a borehole drilled into the formation. The method includes the steps of obtaining a first pressure value at a first depth in the borehole, obtaining at least one further pressure value subsequent to the first pressure value during withdrawing or advancing the logging instrument in the borehole, and determining one or more characteristics of the subsurface formation, utilizing at least one of the further pressure values, or a change in pressure (??) between the first pressure value and a said further pressure value or values, or a change in pressure (??) between a said further pressure value and another said further pressure value, or a combination of two or more of such values.

Abstract: A method of hydraulic fracturing geometry evaluation, comprising injecting a fracturing fluid comprising a magnetic material into a fracture, measuring a field affected by the fracturing fluid in the fracture, and modeling, based on the measuring, a geometry of the fracture.

Abstract: A steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna.

Abstract: Apparatuses and methods are provided herein that may improve sensitivity to transient signals. For example, an electromagnetic sensor for downhole measurements that includes a plurality of sectors (e.g., four quadrants) is provided herein. Each quadrant may include a magnetic core formed of a material with a high initial magnetic permeability to improve sensitivity to transient signals. A sensor for continuous wave induction tools is also provided, and may include a magnetic core formed of a material with a high initial magnetic permeability. Forming each sector magnetic core of a material with a high mechanical reliability may allow the magnetic core of the corresponding sensor to be pliable and flexible and not brittle and prone to breaking. Furthermore, the corresponding sensor may have enhanced sensitivity, greater stability of sensitivity relative to temperature changes, and high mechanical reliability.

Abstract: Systems and methods for performing bed boundary detection and azimuthal resistivity logging using a logging tool with a pair of tilted receiver antennas having a midpoint on a longitudinal axis of the logging tool, a first pair of transmitter antennas symmetrically spaced from said midpoint, and a third tilted receiver antenna positioned farther from said midpoint than the transmitter antennas. Method embodiments include energizing each transmitter antenna of the first pair in a firing sequence and obtaining, responsive to the energizing, measurements with a pair of tilted receiver antennas equally spaced from said midpoint. Methods may also include obtaining, responsive to energizing of a more distant one of the first pair of transmitter antennas, measurements with a third tilted receiver antenna positioned farther from the midpoint than the transmitter antennas.

Abstract: Methods, systems, devices, and products for evaluating a downhole fluid in a borehole intersecting an earth formation. Methods include using ultrasonic irradiation to produce sonoluminescence from cavitation in a volume of the fluid; obtaining spectral information from measurement of the sonoluminescence with a light-responsive device; and estimating a parameter of interest of the fluid from the spectral information. The parameter may be a composition of the fluid or concentration of: i) at least one chemical element in the volume; i) at least one molecular element in the volume. Methods include deconvolving a response spectrum by using one or more separately determined standard spectra, or estimating the parameter of interest using spectral lines represented by the spectral information.

Abstract: A steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna.

Abstract: A method for obtaining full tensor gain compensated propagation measurements includes processing a full tensor voltage measurement to obtain a fully gain compensated tensor quantity. An electromagnetic logging tool including at least first and second axially spaced transmitters and at least first and second axially spaced receivers is rotated in a subterranean borehole. A plurality of voltage measurements are acquired while rotating to obtain a full tensor voltage measurement which is in turn processed to obtain the fully gain compensated tensor quantity.

Abstract: A method for obtaining full tensor gain compensated propagation measurements includes processing a full tensor voltage measurement to obtain a fully gain compensated tensor quantity. An electromagnetic logging tool including at least first and second axially spaced transmitters and at least first and second axially spaced receivers is rotated in a subterranean borehole. A plurality of voltage measurements are acquired while rotating to obtain a full tensor voltage measurement which is in turn processed to obtain the fully gain compensated tensor quantity.

Abstract: A downhole pressure sensor to measure absolute pressure in an annulus and a method of measuring absolute pressure in an annulus are described. The sensor includes an inductor including primary windings and secondary windings, and a capacitor coupled to the secondary windings and disposed in the annulus, at least one of the plates of the capacitor being flexible. The sensor also includes a controller coupled to the primary windings, the controller introducing an input signal to the primary windings and receive a return signal from the primary windings, the return signal resulting from the input signal being transferred through the secondary windings to the capacitor and back through the secondary windings to the primary windings. The controller determines the absolute pressure from the return signal.

Abstract: Various embodiments include apparatus and methods to operate an induction measurement process in a borehole that addresses direct coupling of a signal between sensors of a measuring tool. Apparatus and methods can include a processing unit to generate formation parameters from signals received in the measurement tool. Additional apparatus, systems, and methods are disclosed.

Abstract: An example method includes positioning a first conformable sensor proximate to a downhole element. The first conformable sensor may include a flexible material, with first and second transmitters and first and second receivers coupled to the flexible material. A first signal may be generated using the first transmitter and a second signal using the second transmitter. A first response of the downhole element to the first signal and a second response of the downhole element to the second signal may be measured at the first receiver. A third response of the downhole element to the first signal and a fourth response of the downhole element to the second signal may be measured at the second receiver. At least the first, second, third, and fourth responses may be combined into a compensated response of the downhole element. The compensated response may be processed to determine a parameter of the downhole element.

Abstract: A borehole while-drilling electromagnetic tomography advanced detection apparatus includes a site host, a drilling rig, a detecting pipe screwed coupling on one end to a drilling stem of the drilling rig, a drilling bit screwed coupling to the other end of the detecting pipe, wherein the detecting pipe is provided with a probe comprising a transmitting coil, a receiving coil, an electromagnetic transmitting module, an electromagnetic receiving module, a SCM (Single Chip Microcomputer), a 3D electronic compass, a network interface of the probe and a first memory, in which the memory port of the SCM is connected to the first memory, and the network interface of the probe can be data-communicated with the site host.

Abstract: An MWD system with a BHA sensor assembly that can be assembled and tested off-site and then transported to the field and that requires fewer on-site workers to install and operate the system. The BHA sensor assembly can include a sensor for monitoring at least one physical parameter of the BHA and a processor for collecting the data from the sensor, analyzing the data to determine whether a physical condition has been met, and, if so, activating the telemetry system to begin transmitting drilling information to the surface. In some embodiments, a determination that a physical condition has been met can be used to activate or discontinue local logging of data to memory. Data from sensors can also be used to trigger a modification of the types and/or rates of data that are transmitted to the surface and/or logged to memory.