Abstract: The invention relates to a method of determining a crack at an edge of a metallic material, the edge having a curvature with a radius. The method including: feeding and controlling a current to a transmitter coil for generating a magnetic field in the metallic material, detecting the magnetic field by means of a receiver coil, which detected magnetic field thereby generates a signal) in the receiver coil, determining first, second and third signal values of the signal at a first time, a second time and a third time, respectively, determining a possible presence of a crack and its crack depth based on the first, second and third signal values by means of determining a characteristic relation between the signal values.

Abstract: A method for determining depth of a material is disclosed. The method includes transmitting a signal from an antenna at a location. The signal includes a fundamental frequency and the signal penetrates ground under the location. The location is selected to locate a material at a depth under the location. The fundamental frequency matches a known resonant frequency of a resonant atom of a molecule of the material. The method includes detecting a reflected wave on the antenna, determining a time difference between transmission of the signal and detection of the reflected wave on the antenna, and determining the depth to the material based on the time difference and a reflected velocity corresponding to the resonant atom.

Abstract: A sensor for measuring electrochemical impedance includes a primary circuit that includes a primary electrically conducting coil and a secondary circuit that includes a secondary electrically conducting coil. The primary electrically conducting coil is inductively coupled to the secondary circuit. During operation, the secondary electrically conductive couple has contact electrodes that contact a medium for which the impedance is to be measured. An alternating current source energizes the primary electrically conducting coil during impedance 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: A method and system for electromagnetic method (EM) signal detection based on an onshore sparker source, the method including: arranging an EM signal detection system near a sparker source; releasing, by the sparker source, an electromagnetic pulse concomitantly in a discharge and mechanical energy output process; observing an electromagnetic response generated by the earth under the excitation of the electromagnetic pulse by means of the EM signal detection system for extracting distribution information of geo-electrical parameters; when the sparker source moves, moving the electromagnetic method signal detection system to a new position along with the sparker source while keeping their positions relative to each other unchanged; and repeating the above process after the movement is completed. According to the technical solution of the present invention, fine electromagnetic detection results can be obtained while seismic detection is carried out.

Abstract: An electromagnetic wave detection apparatus (10) includes an irradiator (11), a first detector (17), a propagation unit (20), a memory (13), and a controller (14). The irradiator (11) irradiates electromagnetic waves. The first detector (17) detects reflected waves of the electromagnetic waves irradiated onto an object (ob). The propagation unit (20) includes propagation elements (px). By irradiation position of the electromagnetic waves irradiated onto the object (ob), the propagation elements (px) switch between propagating and not propagating the reflected waves of the electromagnetic waves towards the first detector (17). The memory (13) stores related information. The controller (14) updates the related information based on the position of the propagation element (px) that is propagating the reflected waves toward the first detector (17) when the first detector (17) detects the reflected waves.

Abstract: Estimating an earth response can include deconvolving a multi-dimensional source wavefield from near-continuously recorded seismic data recorded at a receiver position. The deconvolving can include spreading the near-continuously recorded seismic data across a plurality of possible source emission angles. The result of the deconvolution can be the earth response estimate.

Abstract: When the heading machine tunnels, a current generated by a current excitation source enters a coal seam through a movable cutting pick to form a stray current. The stray current collected by a backflow net returns to a negative electrode of a power supply through a transition resistor. When information such as the water content of the coal seam changes, the stray current and a potential difference across the transition resistor also accordingly change, and the coal seam water content information is converted into an electric signal. When the potential difference across the transition resistor is applied to two ends of a piezoelectric ceramic, the piezoelectric ceramic extends or compresses, and the electric signal is converted into a strain signal. A sensing optical fiber converts the strain signal into an optical signal detectable by a photoelectric detector. The optical signal is analyzed to obtain the coal seam water content information.

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: A downhole system includes a first module having a transmitter that transmits at least one sync control signal. The system also includes a second module having a sync module with a direct digital synthesizer (DDS). The sync module analyzes the at least one sync control signal to identify at least one of a sync frequency and a sync phase. The DDS adjusts a local receiver clock based on the identified at least one of a sync frequency and a sync phase.

Abstract: A linear array of underwater radio frequency (RF) antennas is implemented, which emit surface electromagnetic waves propagating along either water-air or water-seafloor interface. The phase difference ?? between neighboring antennas defines the overall beam direction, while the so-formed directional beam intensity remains almost constant near the antenna array due to the largely two-dimensional character of beam propagation. By adjusting the phase difference ??, the narrow two-dimensional surface beam may be sent in any direction over 360°, thus enabling targeted RF communication with any desired object located near the said interface. An impedance matching enclosure filled with an impedance matching fluid may also be utilized surrounding the antennas to reduce antenna dimensions and improve coupling of electromagnetic energy to the surrounding salt water medium, thereby improving underwater radio communication performance.

Abstract: A method of and apparatus for processing received radiation (e.g. RADAR radiation) reflected from a target, the method comprising generating a set of predicted targets, the set of predicted targets comprising at least one member, each member representing a state of the target, generating a predicted waveform for the radiation for each member dependent upon the state of the target, and comparing each predicted waveform with a waveform of the received radiation to determine the accuracy with which the state of the target represented by the member for which the predicted waveform was generated matches an actual state of the target.

Abstract: Apparatuses and methods are described, such as for aligning downhole measurements. Apparatuses and methods include an arrangement of at least two tilted transmitters and at least one tilted receiver along a longitudinal axis of the tool. A first and second plurality of azimuthal measurements are processed to provide a first and a second plurality of higher order mode signals configured to be time-shifted.

Abstract: A device for surveying the condition of a substrate, in particular a soil sensor, having at least one transmitting coil and at least one, preferably four, receiving coils. The transmitting coil is arranged to generate an electromagnetic primary field and the receiving coil is arranged to receive the electromagnetic secondary field induced in the substrate by the primary field. The transmitting coil and the receiving coil are arranged in a housing which includes electromagnetic radiation shielding material. Also disclosed is an agricultural driven machine including a soil sensor and a method for operating a driven machine.

Abstract: A method of borehole correction for water-based mud includes conveying an induction logging tool along a borehole through a formation, obtaining one or more formation measurements using the tool, obtaining a water-based mud conductivity, performing an oil-based mud inversion on the formation measurements to determine an inverted formation conductivity, calculating a corrected formation conductivity using the water-based mud conductivity and the inverted formation conductivity, and displaying a log based at least in part on the corrected formation conductivity.

Abstract: A method includes cementing a target well with a target well cement comprising resistive cement having resistivity that is greater than a resistivity of a subsurface formation through which the target well passes. The method includes injecting an injected signal into a conductive casing material at least partially surrounded by the target well cement. The method also includes receiving a resulting signal that results from the injecting at a signal receiver disposed within at least one of the target well and a drilling well separated from the target well.

Abstract: A system and method for geophysical data collection, for use with resistivity and induced polarization. The system and method include the use of a single voltage reference wire to which all voltage recorders or nodes are connected by means of a piercing wire connector, the voltage recorders providing a measurement of the potential voltage between the reference wire and the ground and allowing for calculation of relative voltage potentials between adjacent recorders.

Abstract: A first time difference calculation unit calculates a time difference ?t1 between the timing of detection of vibration that indicates the first vibration mode of a pipe P and the timing of detection of vibration that indicates a second vibration mode of the pipe P by processing a result of a measurement . A second time difference calculation unit calculates a time difference ?t2 between the timing of detection of vibration that indicates the first vibration mode of the pipe P and the timing of detection of vibration that indicates the second vibration mode of the pipe P by processing a result of another measurement. A leakage position calculation unit uses the time differences ?t1, ?t2, and a space interval I between the first vibration detection unit and the first time difference calculation unit to calculate a leakage position in the pipe P.

Abstract: Some embodiments relate to power detector including a voltage sensor configured to detect a voltage of a load and a current sensor configured to detect a current of the load. The power detector also includes circuitry configured to introduce a phase delay between the detected voltage of the load and the detected current of the load, thereby producing a voltage measurement and a current measurement. The circuitry is also configured to multiply the voltage measurement and the current measurement.

Abstract: An apparatus. At least some illustrative embodiments are an apparatus comprising a sensor streamer. The sensor streamer includes at least one seismic streamer section and a first electrode adapter removably attached to the at least one seismic streamer section. The first electrode adapter includes a first electrode, wherein the first electrode is configured to couple to electrical circuitry configured to measure a potential difference between the first electrode at a first potential and a second potential. The conducting member forms a reference potential, wherein the conducting member is floating. The at least one seismic streamer section is without electromagnetic field-sensing components.

Abstract: An electromagnetic (EM) receiver system for measuring EM signals. The EM receiver system includes a frame; a first EM receiver attached to the frame and configured to measure the EM signals within a first frequency range; and a second EM receiver attached to the frame and configured to measure the EM signals within a second frequency range. Corresponding axes of the first and second EM receivers are substantially parallel to each other.

Abstract: In one aspect, a modular air sampling system includes a sensor module defining a nose, the sensor module including a sensor for sampling contaminants in the atmosphere. A processing and sending module includes processing electronics in communication with the sensor for receiving a signal from the sensor representative of sampled contaminants in the atmosphere. The processing and sending module further includes a radio frequency transmitter operably coupled to the processing electronics for transmitting a radio frequency signal representative of one or more contaminants sensed by the sensor. In another aspect, a modular air sampling system includes a sensor module containing the sensor, processing electronics, and radio frequency transmitter within the sensor module housing.

Abstract: The present disclosure generally relates to a wireless communication system that provides lower peak to average power ratio (PAPR). In particular, the present disclosure pertains to communication systems and methods for achieving low peak to average power ratio (PAPR) for transmitted symbols of wireless devices. In an aspect, the present disclosure relates to transmitter of a communication system, wherein the transmitter can include a source encoding module that is configured to generate source coded symbols from information to be transmitted by the transmitter, a preset values based multiplication module that is configured to multiply M symbols from the generated source coded symbols with M preset values to generate a first set of multiplied samples, and an N-point IDFT module that is configured to process the first set of multiplied samples to obtain a first set of inverse discrete Fourier transform (IDFT) samples for onward transmission to a receiver.

Abstract: Systems and methods for calibrating resistivity tools in environments with radio-frequency (RF) noise are described herein. The method may include receiving a first measurement from a resistivity tool. The measurement may be taken with the resistivity tool elevated to reduce ground effects on the measurements. The first measurement may be altered by excluding at least some RF noise from the first measurement. The RF noise may be a by product of the resistivity tool being elevated. Additionally, the resistivity tool may be calibrated using the altered first measurement.

Abstract: Methods and data acquisition systems enable joint acquisition of seismic and electromagnetic data in a target area using stand-alone digital recorders.

Abstract: A system that incorporates the subject disclosure may include, for example, a circuit for determining a magnitude difference between a first signal supplied to an antenna and a second signal radiated by the antenna, determining a phase difference between the first signal supplied to the antenna and the second signal radiated by the antenna, measuring a change in reactance of an antenna, detecting an offset in an operating frequency of the antenna based on one of the magnitude difference, the phase difference, the change in reactance, or any combination thereof, and adjusting a resonant frequency of the antenna to mitigate the offset in the operating frequency of the antenna. Other embodiments are disclosed.

Abstract: Apparatus and methods are described, such as for obtaining information indicative of a formation resistivity using an electromagnetic formation evaluation tool apparatus. For example, the electromagnetic formation evaluation tool apparatus includes exciter electrodes configured to transmit and receive a formation current. A first exciter electrode may be insulated from a conductive apparatus housing and a second exciter electrode may be coupled to the conductive apparatus housing. Monitor electrodes may be insulated from the conductive apparatus housing. A receiver circuit may be coupled to the monitor electrodes and configured to measure a voltage differential between the monitor electrodes. A power amplifier circuit may be coupled to the first exciter electrode and the conductive apparatus housing and configured to generate the formation current wherein the conductive apparatus housing provides a return path to the power amplifier circuit for the formation current.

Abstract: An exploration paradigm for detecting and/or characterizing gas hydrate deposits using either electromagnetic or seismic surveys, that accounts for the possibility that gas hydrate may accumulate in vertical or subvertical dikes. Geologic factors, such as the presence of the gas hydrate stability zone, indications that a prolific source of gas exists (or existed) below the gas hydrate stability zone and indications that a high flux of gas could be transported into the gas hydrate stability zone, may be considered as part of an exploration strategy. Data may be collected using seismic techniques, such as a walk-away vertical seismic profile techniques, or electromagnetic surveys that are adapted to detecting the presence of vertical or subvertical dikes. In one example, data processing and acquisition techniques may be adapted to detect hydrate dikes, and do not assume a horizontally isotropic earth model.

Abstract: An electromagnetic survey acquisition system includes a sensor cable and a source cable, each deployable in a body of water, and a recording system. The sensor cable includes an electromagnetic sensor thereon. The source cable includes an electromagnetic antenna thereon. The recording system includes a source current generator, a current sensor, and an acquisition controller. The source current generator powers the source cable to emit an electromagnetic field from the antenna. The current sensor is coupled to the source current generator. The acquisition controller interrogates the electromagnetic sensor and the current sensor at selected times in a synchronized fashion.

Abstract: Systems and methods involve generating a baseband signal, up-converting the baseband signal to a radar signal frequency, filtering a lower sideband of the up-converted signal, and transmitting the filtered up-converted signal. Systems and methods also involve receiving a return signal, down-converting the return signal using a signal having a frequency offset from the up-converted signal, filtering the upper sideband of the down-converted return signal, and producing a baseband return signal.

Abstract: An underwater antenna assembly (or array thereof) suitable for subsurface RFID tag interrogation in flowing water such as a river. In preferred embodiments, the antenna interrogates RFID tags implanted in aquatic species. The antenna resides in an elongate antenna housing whose cross-sectional shape is preferably a hydrodynamic teardrop shape. A first end of the housing is linked to a pivoting mechanism such that when the pivoting mechanism is held substantially stationary with respect to the water flow, the second end of the housing is free to rotate generally about the first end in a substantially vertical plane parallel to the water flow direction. The length of the antenna housing is advantageously selected to enable the antenna to monitor for signals across substantially the entire water depth.

Abstract: Formation wettability is quantifiably estimated from measurements of dielectric constant and conductivity. In particular, wettability state of formation rock in a subterranean environment is estimated from multi-frequency measurements of rock dielectric constant and conductivity. A dielectric dispersion model is used to invert the measurements and estimate the saturation exponent. The resulting saturation exponent is used to quantify wettability, e.g., by calculating a wettability index.

Abstract: A system, method and device may be used to monitor conditions in a borehole. Well tubing and casing act as a conductive pair for delivering power to one or more downhole active sensors. At the surface, power and signal are isolated so that the same conductive pair may act to transmit the sensor signals to the surface. In an embodiment, the sensor signals are RF signals and the surface electronics demodulate the RF signals from the sensor power.

Abstract: A method of surveying the condition of an underground enclosure including the steps of: (a) positioning at least one transmitter/receiver unit (including an antenna) within an underground, substantially nonconductive enclosure, such that a substantial air gap exists between the antenna and the inner wall of the enclosure; (b) transmitting an ultra wideband (UWB) signal toward at least a portion of the inner wall; and (c) processing the return signal in order to identify the interface between the soil and a region of conductivity different from the soil.

Abstract: Devices and processes provide for geophysical oil, gas, or mineral prospecting and subsurface fluid monitoring, using a controlled source electromagnetic system that transmits a designed probe wave to create images of sub-surface structures and fluids either statically or while in motion.

Abstract: Systems and method for near-field millimeter wave imaging are provided, in particular, near-field millimeter wave imaging systems and methods that enable sub-wavelength resolution imaging by scanning objects with sub-wavelength probe elements and capturing and measuring phase and intensity of reflected energy to generate images.

Abstract: The present disclosure describes various geophysical survey systems and methods for mapping an electric potential field. At least one illustrative embodiment includes an electromagnetic (EM) source and geophysical survey cables that each includes multiple electrodes spaced apart along each geophysical survey cable's length, and multiple data acquisition units that each obtains measurements indicative of an electric potential between two the electrodes. A modeling module is included and configured to calculate a reference potential at a selected electrode for each of the plurality of geophysical survey cables, as well as a calculation module to combine signals representative of the measurements to produce signals indicative of the electric potential of each electrode relative to the reference potential.

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 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 the signal received by the receive antenna. A homogeneous part of the electromagnetic signal may be reduced, to thereby increase a depth of detection of the characteristic.

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: Disclosed are methods and apparatus for adaptive source electromagnetic (EM) surveying. In accordance with one embodiment, a source waveform signal is generated, and an outgoing EM signal which is based on the source waveform signal is transmitted using an antenna. A responsive electromagnetic signal is detected using at least one electromagnetic sensor, and a receiver waveform signal based on the responsive electromagnetic signal is obtained. A feedback control signal which depends on at least one input signal is determined. Based on the feedback control signal, the source waveform signal is adapted. Other embodiments, aspects, and features are also disclosed.

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 method of sensing exposure to one or more of a plurality of environmental factors includes exposing a code circuit to at least some of the environmental factors, the code circuit disposed over a substrate and including a plurality of electrically-connected sensor patches, each sensor patch susceptible to one of the environmental factors, wherein the code circuit has an electrical state. An electrical excitation signal is passed through the code circuit, and a corresponding received electrical signal detected, using a transceiver formed on a transceiver substrate separate from and disposed over the substrate, wherein the transceiver includes a controller and the received electrical signal depends on the excitation signal and the electrical state of the code circuit. Using the controller, the received electrical signal or a representation thereof is automatically stored in a memory. The checking and storing steps are automatically repeated after one or more selected time intervals.

Abstract: Disclosed are methods and apparatus for adaptive source electromagnetic (EM) surveying. In accordance with one embodiment, a source waveform signal is generated, and an outgoing EM signal which is based on the source waveform signal is transmitted using an antenna. A responsive electromagnetic signal is detected using at least one electromagnetic sensor, and a receiver waveform signal based on the responsive electromagnetic signal is obtained. A feedback control signal which depends on at least one input signal is determined. Based on the feedback control signal, the source waveform signal is adapted. Other embodiments, aspects, and features are also disclosed.

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 method of geophysical prospecting for detecting bodies of fluids in underground formations comprises the steps of activating a seismic energy source (2) to transmit seismic energy into the ground, detecting an electromagnetic signal (14) generated by interaction between the seismic energy and underground formations (12) including fluids, and recording properties of the detected electromagnetic signal against time, so as to record an electromagnetic signal generated by interaction between a secondary energy impulse (10) from the activation of the energy source and underground formations including fluids. The secondary energy impulse propagates to the formations more slowly than the primary seismic waves from the same activation of the energy source travelling at the speed of sound as attenuated by the materials through which they pass. The detected electromagnetic signal comprises frequencies in the range 0 to 30 Hz.

Abstract: The present disclosure describes various geophysical survey systems and methods for mapping an electric potential field. At least one illustrative embodiment includes an electromagnetic (EM) source and geophysical survey cables that each includes multiple electrodes spaced apart along each geophysical survey cable's length, and multiple data acquisition units that each obtains measurements indicative of an electric potential between two the electrodes. A calculation module is included and configured to combine signals representative of the measurements to produce signals indicative of the electric potential of each electrode relative to a reference potential assumed to be present at a selected electrode for each of the plurality of geophysical survey cables. Each reference potential is assumed to be of a magnitude that is within a tolerance range of a common reference potential.

Abstract: Method for assessing hydrocarbon source rock potential of a subsurface region without well log information. The method uses surface electromagnetic (121) and seismic (122) survey data to obtain vertical profiles of resistivity and velocity (123), which are then analyzed in the same way as well log data are analyzed by the well known Delta Log R method (124).

Abstract: The present disclosure relates to determining a property, such as resistivity, of an earth formation. A transmitter is disposed in a wellbore penetrating the formation, and a plurality of receivers are distributed on or near the earth's surface. The transmitter sends electromagnetic energy into the formation and the resulting signal, after passing through the formation, is detected by the array of receivers. The received signal is used to determine the property of the formation. This is often achieved using an inversion or numerical model of the formation being measured. The inversion takes into account changes in the background formation model due to transmitting from various locations. The measurements made on the formation can be performed while drilling the wellbore or subsequent to the drilling.

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.