Abstract: A marine electromagnetic survey source includes a power cable configured to couple to a high voltage power supply at one axial end and to a head unit at the other axial end. The head unit includes equipment configured to output a lower voltage at higher current than the current imparted thereto by high voltage power supply. The head unit has an electrically conductive exterior coupled to one output terminal of the equipment. An electromagnetic antenna cable having an electrode thereon is coupled to the head unit and configured to receive the output of another terminal of the head unit equipment. In some implementations, electromagnetic fields are induced in formations by conducting current to the equipment. Marine geophysical surveys are conducted utilizing such induction of electromagnetic fields.

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: 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: 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: An electromagnetic sensor streamer may include a jacket, at least one electromagnetic sensor in operational communication with a voltage measuring circuit disposed inside the jacket, and at least one wire coil. The at least one wire coil is in signal communication with the voltage measuring circuit, and the voltage measuring circuit is configured to determine motion-induced voltages imparted to the at least one electromagnetic sensor in the streamer.

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 towing marine geophysical sensor streamers in a body of water includes moving a towing vessel at a selected speed along the surface of the body of water. At least one geophysical sensor streamer is towed by the vessel at a selected depth in the water. A velocity of the streamer in the water is measured at at least one position along the streamer. The selected speed of the towing vessel is adjusted if the measured velocity is outside of a selected range.

Abstract: Depth and tilt control systems for geophysical sensor streamers and methods of use are discussed. Such systems may include a plurality of tilt sensors disposed at spaced apart locations along the geophysical sensor streamer, each tilt sensor having a first tilt sensing element arranged to measure tilt of the geophysical sensor streamer proximate the associated spaced apart location, a plurality of LFD control devices, each disposed proximate one of the tilt sensors along the geophysical sensor streamer, and a plurality of microcontrollers, each microcontroller in signal communication with at least one of the LFD control devices and its associated tilt sensor, wherein each microcontroller is capable of utilizing the tilt measured by the associated tilt sensor to selectively operate the associated LFD control device to cause the geophysical sensor streamer to align with a selected depth profile.

Abstract: A method for making a marine electromagnetic survey streamer includes affixing connectors to longitudinal ends of a strength member. At least one signal communication line is extended along the length of the strength member. The strength member, connectors, and at least one signal communication line form a mechanical harness. Electrodes are affixed to the mechanical harness at selected positions. The mechanical harness is drawn through a co-extruder. The co-extruder fills void spaces in the harness with a void fill material. The co-extruder applies a jacket to an exterior of the void filled harness.

Abstract: A method for electromagnetic surveying below the bottom of a body of water includes deploying a plurality of nodal recording devices in a selected pattern on the water bottom. An electromagnetic transmitter is towed in the water. At least one electromagnetic sensor streamer is concurrently towed in the water. The electromagnetic transmitter is actuated at selected times and signals detected by sensors in the nodal recording devices and in the at least one streamer are recorded.

Abstract: A disclosed electromagnetic survey system includes one or more streamer(s) having multiple electromagnetic sensors and motion sensing units. Each motion sensing unit has one or more accelerometer(s) to measure motion perpendicular to an axis of the streamer, and a rotation sensor to measure rotation about the axis. The measurements of the accelerometer are adjusted based on measurements from the rotation sensor. The survey system also includes one or more processor(s) that determine, for each electromagnetic sensor, a motion signal based on the adjusted measurements. A described electromagnetic survey method includes processing acceleration and rotational motion measurements to obtain an orientation of motion sensing units as a function of time. The measured acceleration is manipulated based on the orientation to obtain one or more velocity signal(s) for each motion sensing unit. Interpolation is performed on the velocity signals to determine at least one velocity signal for each electromagnetic sensor.

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 electromagnetic receiver cable includes a plurality of signal processing modules disposed at spaced apart locations along the receiver cable. A power supply line is connected to each of the signal processing modules and to an electric current source. A current regulation device is connected in the power supply line proximate each signal processing module. The current regulation devices are connected such that an amount of current flowing through the power supply line is substantially constant. At least one electromagnetic receiver is functionally coupled to an input of each signal processing module.

Abstract: A method for acquiring electromagnetic data in at least two dimensions includes towing a first streamer cable behind a vessel in a body of water, the first streamer cable including a reference line extending substantially along the entire length thereof, a plurality of spaced apart measuring electrodes electrically insulated from the reference line and a voltage measuring circuit functionally coupled between each measuring electrode and the reference line. At least a second streamer cable is towed at corresponding distance from the vessel. The second streamer cable is configured substantially as the first streamer cable. The second streamer cable is displaced from the first streamer cable in one of a horizontal plane and a vertical plane. At selected times an electromagnetic field is imparted into the water.

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 towing marine geophysical sensor streamers in a body of water includes moving a towing vessel at a selected speed along the surface of the body of water. At least one geophysical sensor streamer is towed by the vessel at a selected depth in the water. A velocity of the streamer in the water is measured at at least one position along the streamer. The selected speed of the towing vessel is adjusted if the measured velocity exceeds a selected threshold.

Abstract: A marine electromagnetic sensor cable includes a first jacket covering an exterior of the cable. At least one wire loop is disposed on the exterior of the first jacket. The wire loop is shaped to have a magnetic dipole moment along a selected direction. A contact ring is disposed inside the first jacket to make electrical connection between the at least one wire loop and an associated signal processing circuit disposed inside the first jacket.

Abstract: A method for operating a geophysical sensor streamer in body of water includes operating a remotely operated vehicle coupled to a forward end of the streamer to tow the streamer in the water. Signals generate by sensors on the streamer are communicated substantially in real time to a recording unit on a survey vessel using at least one of electrical and optical cables in an umbilical cable connecting the remotely operable vehicle to the survey vessel.

Abstract: A depth and level control system for a geophysical streamer according to one aspect of the invention includes a plurality of tilt sensors disposed at spaced apart locations along the streamer. The tilt sensors each have a first tilt sensing element arranged to measure tilt of the streamer along a longitudinal dimension thereof. A controller is in signal communication with each tilt sensor. A depth control device is in signal communication with each controller. The controller is programmed to operate the depth control device to cause the streamer to be level as measured by the tilt sensor.

Abstract: A receiver streamer system for marine electromagnetic surveying includes a first streamer, and a second streamer disposed substantially parallel to and spaced apart from the first streamer. A first pair of electrodes is associated with the first streamer and a second pair of electrodes is associated with the second streamer. Each of the first and second pairs of electrodes is functionally associated with a voltage measuring circuit configured to measure voltage along an inline direction. At least one electrode on each of the first and second streamers is configured and associated with a voltage measuring circuit to make voltage measurements in a cross-line direction.