Abstract: An electromagnetic sensor cable has components including a first sensor cable segment having a plurality of spaced apart electrodes on the first sensor cable segment an electrical conductors coupled to the electrodes such that at least one of the electrodes is electrically connectible at at least one longitudinal end of the first sensor cable segment. The sensor cable includes a second sensor cable segment configured substantially the same as the first sensor cable segment. A first signal processing and configuration module has signal processing circuitry configured to perform at least one of measuring voltages across selected pairs of electrodes, and communicating signals representative of voltages measured across selected pairs of electrodes. The cable components are each configured to connect at the lateral ends one to another.

Abstract: Cost-effective compact magnetometers can be deployed across large ocean areas to record magnetic field strengths. Each magnetometer has a canister containing a magnetometer sensor at its upper end to detect magnetic field strengths of magnetic influence sweep systems and provide representative data signals. Each magnetometer also has sensors to collect data representative of the orientation of the magnetometer as well as temperature and depth to aid in post operational evaluation of the gathered magnetic strength data. A computer processor connected to the sensors controls receipt of the data signals and stores them in a memory device. Batteries at the canister's lower end supply power for the sensors, processor, and memory. An anchor release mechanism causes an anchor to separate from the canister, allowing it to float to the surface for recovery or to transmit data via a UHF transceiver.

Abstract: A marine sensor streamer includes a jacket covering an exterior of the streamer. At least one strength member extends the length of the jacket. At least one stiffener element extends inside the length of the jacket. The at least one stiffener element includes a gas filling the interior of a flexible, compressible tube and filler elements disposed in the gas. The filler elements have exterior shape and surface roughness such that upon compression of the gas, the filler elements are urged into contact with each other, causing the streamer to become substantially rigid.

Abstract: A method for electromagnetic geophysical surveying of rock formations (1) under a sea-floor (3) comprising the following steps: *—towing first and second alternating field (E1, E2) emitting sources (s1, S2) in first and second depths below the sea surface, said first field (E1) having a first phase (?1);—said second alternating field (E2) given a second phase (?2) different from said first phase (?1), said sources (S1, S2) constituting a phased array emitter antenna with directivity for transmitting a major proportion of the combined electromagnetic energy downwards;—said first and second fields (E1, E2) for propagating partly down through the sea-floor (3) and being reflected and/or refracted through said rock formations (1) and partly propagating back through the seafloor (3);—said first and said second fields (E1, E2) for merging to a total field and being measured by electromagnetic receivers (r1, r2, . . . , rn) recording corresponding field registrations (Er1(t), Er2(t), Er3(t), . . . , Ern(t)).

Abstract: Method for improving frequency-domain (1505), controlled-source electromagnetic data readability and interpretability in hydrocarbon prospecting by mapping a scaled amplitude or the relative amplitude (or phase) of the electromagnetic field in a scaled offset?scaled frequency plane (1510). The preferred mapping space uses the offset times the square-root of the frequency as the X-axis and the square-root of the frequency as the Y-axis. The preferred way to scale the amplitude of the electric field is to multiply it by the frequency to the power of ?1.5. Resistive anomalies in the data may be identified by comparing negative offset data (or data relative to a reference) to positive offset data (1515). The location and size of a potentially hydrocarbon-bearing resistive body may be estimated from the position of the anomaly on the map (1520).

Abstract: A survey module includes at least one sensing element to measure a first electromagnetic (EM) field along a first direction, and circuitry to derive a second EM field along a second, different direction based on the first EM field.

Abstract: Apparatus and method for estimating the 3D orientation angles for remotely deployed devices with flexible arms such as dipole antennas of receivers used in marine controlled-source electromagnetic surveys to explore for hydrocarbons. Acoustic transponders or transducers, or other positioning sensors such as attitude sensors or strain-sensitive fiber optic cables are placed on each electrode arm of the receiver. Acoustic sensors (101) on the receiver frame (94) work in conjunction with the positioning sensor(s) (101) on the electrode arms (92) to provide accurate 3D spatial position of the receiver electrodes (93) relative to the receiver frame. Alternatively, sonar transducers mounted on the frame are used to image the electrode arms, which image can be enhanced by fixing reflectors to the arms. An attitude sensor is mounted on the receiver frame, enabling conversion of the relative electrode positions to an earth reference frame.

Abstract: The present disclosure relates to methods and systems for detecting electric potential difference in water. A first electrode comprising a first electrode body is configured to be in electrical contact with the water when the device is disposed in the water. A second electrode comprising a second electrode body is configured to be in electrical contact with the water when the device is disposed in the water. An electrical connection exists amongst the first electrode, the second electrode, and a voltage measuring device. At least one of the first electrode body and the second electrode body is formed at least partially of a carbon aerogel material.

Abstract: Method for real time monitoring of the waveform transmitted by an electromagnetic survey source, using a near-source monitoring receiver to measure electromagnetic field and transmitting the measured signal in real time to a control location.

Abstract: A method for estimating the effects of an airwave in marine electromagnetic data measured using a source and at least one receiver. The method involves measuring the electromagnetic response at two different under water source-receiver separations and using measurements at the larger separation to estimate the airwave response at that separation. The airwave effect in the response measured at the shorter separation can then be determined using the estimated airwave response at the larger separation.

Abstract: An electromagnetic geological metrology system comprises: (a) a transmitter arrangement for generating outbound radiation towards a geological formation; (b) a receiver arrangement for receiving reflected electromagnetic radiation reflected from the geological formation and generating corresponding one or more received signals; and (c) a data processing arrangement for processing the one or more received signals, The system is distinguished in that: (d) the transmitter arrangement includes an antenna arrangement coupled via a switching arrangement to an energy storage arrangement; and (e) the switching arrangement is operable to discharge energy stored in the energy storage arrangement for generating the outbound radiation.

Abstract: In order to increase result accuracy the noise effect during vessel motion is reduced, wherefore direct current pulses are excited the parameters of which are set basing on section conductivity and deposit depth, the electric field is measured simultaneously on pairs of receiving electrodes basing on the spatial averaging of potential of double electric layer that is generated on the boundary of electrode and water during the pulses and pauses between them, and geoelectrical parameters are determined.

Abstract: A marine electromagnetic survey system includes a power cable configured to couple to a power supply at one axial end, and to a head unit at the other end. The power supply includes a source of direct current which is coupled to the power cable. The head unit includes equipment configured to output a lower voltage at a higher current than the source of direct current. At least one electromagnetic antenna is coupled to the head unit and is configured to receive the output of the head unit equipment.

Abstract: A method for electromagnetic exploration includes imparting a first electromagnetic signal into subsurface formations and imparting a second electromagnetic signal into the formations substantially contemporaneously with imparting the first electromagnetic signal. The first and second electromagnetic signals are substantially uncorrelated with each other. A combined electromagnetic response of the formations to the first and second imparted electromagnetic signals is detected. A response of the formations to each of the first and the second imparted signals is determined from the detected response.

Abstract: The generator device is proposed for seabed survey, comprising a generator line, including electrodes, a hoist, hydraulic pump, air compressor, and at least one hose joined to the generator line, situated optionally inside or outside the line. The hose includes a through hydro-channel therein, a stationary end connected to the pump or alternatively to the compressor, and a running end furnished with a discharge valve. Connecting to the compressor ensures positive floatation of the generator line, whereas connecting to the pump ensures negative floatation thereof. In preferred embodiments, the device comprises a hydraulic clutch and a faucet. The hose communicates with the pump and compressor through the clutch and faucet, ensuring alternative communication of the hose's hydro-channel with water or air for filling thereof. The generator line comprises a dipole including one power braiding, and an initial part including two power braidings, the braidings are connected to the electrodes.

Abstract: The system and method provided modify a conventional seafloor long-wire electromagnetic (LEM) receiver by increasing the number of discrete antennae placed on the long wire. Two dipoles of electric field data are positioned exactly adjacent to each other, providing input to the same data logger system located within a seafloor survey unit to which the long wire is connected. Highly precise electric field gradients can be obtained by taking the difference of the measurements of the two electrodes, both for amplitude and phase. Any common-mode source of noise, such as magnetotelluric signals and receiver instrument noise will be rejected when the signals from the two electrodes are differenced. An acoustic navigation system utilizes a plurality of transponders to permit triangulation for accurate source-receiver ranging.

Abstract: An electromagnetic (EM) source assembly for performing marine subterranean surveying includes electrodes in an arrangement configured for towing through a body of water. A controller is configured to selectively activate different sets of the plurality of electrodes, where a first of the sets produces an EM field in a first direction, and where a second of the sets produces an EM field in a second, different direction.

Abstract: A device and method for measuring electromagnetic signals that can be used to take measurements at or near the sea floor. The device comprises a central housing, a data management system located within the housing and at least two arms extending outwards from the housing. Each arm comprises a flexible elongate sheath attached to the housing, a sensor head, a flexible electrical cable attached to the sheath and connecting the sensor head to the data management system and a rod which is removeably locatable within the sheath. The rod is connectable relative to the housing at one end and connectable relative to the sensor head at the end remote from the housing.

Abstract: A method for communicating with a receiver during an electromagnetic survey. In one implementation, the method may include sending a survey signal to a subsurface region, wherein the survey signals is a first electromagnetic signal and sending a diagnostic signal to the receiver. The diagnostic signal is a second electromagnetic signal having a diagnostic message.

Abstract: A method for modeling conductivity distribution in a formation below a body of water includes measuring electromagnetic response of the formation with an electromagnetic survey system; measuring at least one of water conductivity, water dielectric constant, and water temperature with respect to depth in the water; generating an initial model of conductivity distribution of the formation; discretizing the measurements of at least one of water conductivity, water dielectric constant, and water temperature with respect to depth into at least one layer; generating a forward model of a response of the electromagnetic survey system to the initial model and the discretized measurements; comparing the forward model to the measured electromagnetic response to determine differences; adjusting the initial model to reduce the differences; and repeating generating a forward model, comparing the forward model to the measured electromagnetic response, and adjusting the initial model until the differences fall below a select

Abstract: A marine electromagnetic geophysical survey transducer cable includes a tow cable configured to couple to a tow vessel. A first electrode cable is coupled at a forward end to the tow cable. A second electrode cable is disposed aft of the first electrode cable and configured to indirectly couple to the tow vessel. At least one of the first and second electrode cables includes a cable core comprising a first core material having a first density selected to provide the transducer cable with a selected overall density, and at least one layer of electrically conductive strands disposed exterior to the cable core.

Abstract: A marine electromagnetic sensor system includes a sensor cable having at least one electromagnetic sensor thereon. A first calibration electrode is disposed on the cable on one side of the sensor. A second calibration electrode is disposed on the cable on an opposite side of the sensor. A calibration power supply is coupled to the first and second calibration electrodes. A measuring circuit is coupled to the sensor. A method for calibrating marine electromagnetic survey electrodes includes imparting electric current between calibration electrodes disposed at spaced apart locations on a cable deployed in the water. Voltages impressed across a pair of electrodes disposed on the cable between the calibration electrodes are detected in response to the current. A change in sensitivity of the at least one pair of electrodes is determined using the detected voltages.

Abstract: A method for determining orientation of an electromagnetic survey sensor includes deploying the sensor at a selected position on the bottom of a body of water. An electromagnetic field is generated at a selected position in the body of water. A portion of the electromagnetic field is detected along at least two orthogonal directions at the sensor. A portion of the detected electromagnetic field is selected as having traveled only in a vertical plane which includes both source position and sensor position. The polarization direction of the selected portion of the electromagnetic field is determined from the selected portion. The determined polarization direction is used to determine the sensor orientation.

Abstract: A method for determining a component of electric field response to a time varying electromagnetic field induced in the Earth's subsurface involves measuring magnetic field gradient in at least two orthogonal directions in response to the induced electromagnetic field and determining an electric field response in a direction normal to the magnetic field gradient measurements.

Abstract: The present invention, in various embodiments, is directed to a geophysical system and method in which a transmitter coil is oriented with its axis horizontally, and a sensor is positioned below the coil to measure an ambient electrical and/or magnetic parameter associated with a conductive medium surrounding the at least one transmitter coil.

Abstract: A method for electromagnetic surveying subsurface formations includes inducing an electromagnetic field in the subsurface formations by passing electric current through a transmitter. Response of the subsurface formations to the induced electromagnetic field is detected at a first plurality of spaced apart positions disposed longitudinally within a bipole length of the transmitter. A direct induction response is removed from the detected response.

Abstract: A method of testing the electric field recording of a marine electromagnetic sensor cable including electrodes is provided. The method includes causing current to flow between a pair of first electrodes disposed along the marine electromagnetic sensor cable. The flow of current generates a voltage that is impressed on a pair of second electrodes disposed along the marine electromagnetic sensor cable. A potential difference between the pair of second electrodes is measured. Accuracy of the electric field recording is inferred from the measured potential difference.

Abstract: A method for determining resistivity distribution of formations below a bottom of a body of water from transient electromagnetic signals acquired by imparting a transient electromagnetic field into the water and detecting an electromagnetic response thereto at a plurality of spaced apart positions from a place of the imparting includes simulating an air wave response at each of the plurality of spaced apart positions. The simulated air wave response is subtracted from the detected response to produce a subsurface impulse response at each of the plurality of positions. The subsurface impulse responses are used to determine the resistivity distribution.

Abstract: A survey apparatus for surveying a subterranean structure includes an electromagnetic (EM) sensing element to measure an EM field received from the subterranean structure, and a sample collector activatable to collect a sample of soil.

Abstract: To perform marine electromagnetic (EM) surveying of a subterranean structure, a marine cable system is provided including a tow cable, a plurality of electromagnetic (EM) sources coupled to the tow cable, and a plurality of EM receivers coupled to the tow cable. The system is configured for deployment in a body of water to perform marine EM surveying of a subterranean structure.

Abstract: A bottom system related to equipment deployed for seabed geo-electrical survey is proposed, in preferred embodiments comprising a basic module, including registration and power supply means, or a combination of the basic module with at least one additional module: a magnetic characteristics measuring module or/and a seismic characteristics measuring module. The additional modules are connected with other modules through hermetic connectors. The modules are attached to a load with Kevlar straps, provided with an electrochemical release system. Arms with electrodes measuring electromagnetic characteristics of seabed, are attached to the basic module, in their initial position directed upwards at minimum 15° from the vertical, and fixed with fixing elements, connected with a releasing element of a device for descending and lifting the bottom station. The arms are made telescopic for convenient transportation.

Abstract: A method for survey of hydrocarbon deposits in a researched profile of sea-bottom comprises providing a generator generating pulse electric current with a generator frequency in a towable generator line exciting electric field signals measured by sea-bottom stations synchronized with the generator, forming space-domain data arrays for the generator frequency and for higher odd harmonics frequencies nearest thereto, forming time-domain data arrays for selected offsets, inversion of the time-domain and space-domain data, and determining a bottom strata resistivity and polarization characteristics for the researched profile, based the inversion's results. The inversion preferably encompasses synchronizing and adjusting the generator line and electric field signals, dividing them into a frequency branch, including a fast Fourier transform and a robust summation producing the space-domain arrays, and a time-domain branch, including a robust summation producing the time-domain arrays.

Abstract: To perform an electromagnetic (EM) surveying of a subterranean structure, a signal generator produces a signal having an analog continuous waveform without steps in the waveform. Producing the signal is in response to an indication specifying a characteristic of the signal. An antenna is responsive to the signal having the analog continuous waveform to emit an EM field to produce the EM surveying of the subterranean structure.

Abstract: A system for measuring electrical resistivity survey checks a border of bedrock or a thickness of a sedimentary layer in a riverbed of a river or lake within a short time. A method for analysis of an underground structure of a riverbed using the same is also provided. The system for streamer electric resistivity survey using a survey boat includes a streamer cable connected to the survey boat and having a plurality of electrodes attached thereto, a multi-channel resistivity meter loaded on the survey boat to measure electric resistivity from the plurality of electrodes, a first RTK GPS (Real Time Kinematic Global Positioning System) loaded on the survey boat to measure a position of the survey boat in real time, and a second RTK GPS installed to a tail of the streamer cable to measure a position of the tail in real time.

Abstract: A method for electromagnetic exploration includes imparting a first electromagnetic signal into subsurface formations from a first location and imparting a second electromagnetic signal into the formations from a second location substantially contemporaneously with imparting the first electromagnetic signal. The first and second electromagnetic signals are substantially uncorrelated with each other. A combined electromagnetic response of the formations to the first and second imparted electromagnetic signals is detected at a third location. A response of the formations to each of the first and the second imparted signals is determined from the detected response.

Abstract: A field distributed array of a plurality of underwater sensors are used to detect, preferably using a nanomagnet, slight changes in magnetic fields caused by passing metallic structures, such as submarines. Each sensor is preferably configured to communicate with, e.g., an Unmanned Underwater Vehicle (UUV), which then passes raw or aggregated information to a user (person or computing device). In one possible embodiment, an aircraft deploys hundreds of sensors on the “battlefield” (i.e., in the ocean). Some of the sensors are controlled to sink and anchor to the bottom, while others are controlled to float at a predetermined depth, from which they transmit data about their magnetic environs, such that a map of the geomagnetic field in the area can be generated. This type of distributed sensor system is particularly effective for antisubmarine warfare (ASW) operations across a wide area of a zone of operations.

Abstract: A marine electromagnetic streamer includes a plurality of electrodes disposed along a longitudinal dimension of the streamer. At least one signal processing module is disposed at a selected position along the streamer. A multipole switch associated with the at least one module is electrically coupled between a signal input of the signal processing module and selected pairs of the electrodes. The switch is configured to enable the selected pairs coupled to the switch such that selection thereof results in at least one of selected electrode spacing and selected electrode offset from an electromagnetic energy source.

Abstract: A marine sensor streamer includes a jacket covering an exterior of the streamer. At least one strength member extends the length of the jacket. At least one stiffener element extends inside the length of the jacket. The at least one stiffener element includes a gas filling the interior of a flexible, compressible tube and filler elements disposed in the gas. The filler elements have exterior shape and surface roughness such that upon compression of the gas, the filler elements are urged into contact with each other, causing the streamer to become substantially rigid.

Abstract: An electromagnetic survey sensing device includes at least two electrodes disposed at spaced apart locations. An electrical to optical converter is electrically coupled to the at least two electrodes. The converter is configured to change a property of light from a source in response to voltage imparted across the at least two electrodes. The device includes an optical fiber optically coupled to an output of the electrical to optical converter, the optical fiber in optical communication with a detector.

Abstract: A method for determining a component of electric field response of the Earth's subsurface to a time-varying electromagnetic field induced in the Earth's subsurface is provided. The method includes measuring electric field response along a nonlinear pattern on at least one of the Earth's surface and the bottom of a body of water. The method includes measuring magnetic field response in three directions along the nonlinear pattern on at least one of the Earth's surface and the bottom of the body of water. The method further includes determining an electric field response in a direction normal to the measured electric field response using the electric field response and magnetic field response measurements.

Abstract: A system to perform a marine subterranean survey includes at least one vertical electromagnetic (EM) source and at least one EM receiver to measure a response of a subterranean structure that is responsive to EM signals produced by the vertical EM source. At least one tow cable is used to tow the EM source and EM receiver through a body of water.

Abstract: A sensor cable for surveying. The sensor cable may comprise at least one pair of current sensor electrodes and an amplifier. The current sensor electrodes may be disposed along opposite sides of the sensor cable. The current sensor electrodes may be configured to detect current in an electromagnetic field transverse to an inline direction of the sensor cable. The amplifier may be configured to amplify the current in the electromagnetic field for detection by the electrode pair.

Abstract: A sensor (S) for marine measurements of an electric field, the sensor (S) including at least two electrodes (3, 4); signal transmission means (5) for transmitting measured signals from the sensor (S) to a signal processing (6); at least two closed containers (1, 2) which are formed of a non-conductive material and are filled with an electrolyte (E); at least two flexible hoses (7, 8) formed of an electrically non-conductive material; there being attached in a fluid-communicating manner to each of the containers at least one first hose end (7a, 8a), and a second hose end (7b, 8b) being open and attached to means (9a, 9b) for exact positioning of the second hose end (7b, 8b); the hoses (7, 8) being arranged to be filled with a medium (W) of the same type as that, in which the sensor (S) is arranged to be immersed in an operative condition; and two containers (1, 2) forming a pair of containers, the two containers (1, 2), relatively, being placed close to each other under approximately identical thermal, pressur

Abstract: A method for analyzing acquired electromagnetic measurements (R) made at or in a sea (4) over a seafloor (1) with rock formations (3) having relatively low resistivity (?3) for detecting a possibly underlying petroleum bearing reservoir formation (2) having relatively high resistivity (?2), wherein a low frequency electromagnetic transmitter (5) arranged in the sea (4) emits an electromagnetic field (P) propagating in the sea (4), in the rocks (3, 2) and in the air (0) above the sea; wherein electromagnetic sensors (6) are arranged with desired offsets (x) in the sea (4) for measuring the electromagnetic field (P(x)) while the field propagates, characterized in that one or more component of the electromagnetic field (P) is measured at least one large offset (xL) from the transmitter (5) where the field (P) essentially only has its origin from the field propagating as a field (P0) through the air (0); that the one or more components of the electromagnetic field (P) measured at the large offset (xL) is calculat

Abstract: Method and computer program for accepting controlled-source electromagnetic (“CSEM”) source and receiver data (40) as time series, transforming these data into the time-frequency domain, and reducing these data and survey metadata to a form suitable for interpretation or inversion. The invention includes: a number of processing tools or programs (30), each designed to take a specific action on CSEM data or metadata, combine data types in some way, and/or provide a visual representation of data; a Graphical User Interface (32) to specify the action of specific tools (34) on specific data, supply parameters to tools, and monitor progress of the processing project; and a specified common internal data format, so that processing tools may be applied in various orders (36) during different processing flows and processed CSEM data can be passed on to interpretation or inversion systems.

Abstract: A geophysical sensor cable has one or more sensor cable sections. Each of the sensor cable sections is provided with seismic and electromagnetic sensors arranged along said cable. The seismic sensors include a hydrophone and a seismic component receiver for seismic vector measurements while the sensor cable is at the sea-floor. The electromagnetic sensors include both E-field sensors and H-field sensors. The E-field sensors include pairs of first and second electrodes arranged with different positions along the cable and connected to a voltage amplifier. The H-field sensors include three mutually orthogonally arranged H-field component sensors.

Abstract: A method of electromagnetic surveying of an area of seafloor that is thought or known to contain a subterranean hydrocarbon reservoir is described. The method includes broadcasting an EM signal from a horizontal electric dipole (HED) transmitter and obtaining vertical electric dipole (VED) response data at a remote receiver in response thereto. Survey data are analyzed by comparing the VED response data with background data which are not sensitive to the postulated hydrocarbon reservoir. Accordingly, differences between the VED response data and the background data allow for the identification of buried hydrocarbon reservoirs. The background data may be provided by magneto-telluric surveying, controlled source electromagnetic surveying or from direct geophysical measurement.

Abstract: A source arrangement for generating electrogmagnetic (EM) wavefields, comprising an EM signal generator, at least three electrodes (141-144) connected to the generator, and a control system. The electrodes are spaced apart but not all in line. The control system is arranged to apply non-coincident time-varying signals or transmissions from the generator between different pairs of the electrodes. The non-coincidence can be by applying the signals sequentially or by applying the signals out of phase.

Abstract: A method is disclosed for determining earth vertical electrical anisotropy from offshore electromagnetic survey measurements. The method requires both online and offline data, which includes at least one electromagnetic field component sensitive at least predominantly to vertical resistivity and another component sensitive at least predominantly to horizontal resistivity. Using a horizontal electric dipole source, online EZ and offline HZ measurements are preferred. For a horizontal magnetic dipole source, online HZ and offline EZ data are preferred. magnetotelluric data may be substituted for controlled source data sensitive to horizontal resistivity. Maxwell's equations are solved by forward modeling or by inversion, using resistivity models of the subsurface that are either isotropic or anisotropic.

Abstract: A multi-component field source for surveying subsea formations includes at least two electrodes having a direction of motion, wherein the at least two electrodes are configured to produce an electric dipole in an orientation that is not parallel to both the direction of motion of the electrodes and the seafloor. A method for logging subsea formations includes transmitting electromagnetic energy into the subsea formations with at least two electrodes having a direction of motion and configured to produce an electric dipole in an orientation that is not parallel to both the direction of motion of the electrodes and the seafloor; and receiving signals that comprise electromagnetic energy that has traversed the subsea formations.