Abstract: Electromagnetic streamer cables and methods of use. Example systems include: a first electrode, the first electrode at a first location along the streamer cable; a second electrode at a second location along the streamer cable; a first sensor module electrically coupled to the first electrode and second electrode, the first sensor module configured to measure a voltage across the first and second electrodes; a third electrode at a third location between the first and second electrodes; a fourth electrode at a fourth location along the streamer cable, the fourth location distal to the second location; and a second sensor module electrically coupled to the third electrode and fourth electrode, the second sensor module configured to measure a voltage across the third and fourth electrodes.

Abstract: A marine electromagnetic sensor cable system includes a first sensor cable subsystem including at least a first sensor cable segment. The first sensor cable segment includes a plurality of spaced apart electrodes which electrically contact a body of water when the first sensor cable segment is immersed therein, and an electrical conductor coupled to each electrode, each electrical conductor extending from one longitudinal end of the sensor cable segment to the other. The system includes a first signal processing module electrically coupled to a longitudinal end of the first sensor cable segment, and including a voltage measuring circuit electrically connected between two or more electrodes from the first plurality of electrodes. Marine electromagnetic surveys are conducted using the marine electromagnetic sensor cable system.

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: 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: 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: A method for determining geodetic position of at least one point on a geophysical sensor streamer towed by a vessel in a body of water includes determining geodetic positions of a plurality of locations along a first geophysical sensor streamer towed at a first depth in the body of water. A lateral offset is caused between the first geophysical sensor streamer and a second geophysical sensor streamer towed at a second depth in the body of water. A distance is measured between at least two selected points along the first geophysical sensor streamer and a selected point along the second geophysical sensor streamer. A depth is measured at at least one point along the second geophysical sensor streamer. A geodetic position is determined at a selected point along the second geophysical sensor using the depth measurement, a direction of the lateral offset and the measured distances.

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 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 method for determining geodetic position of at least one point on a geophysical sensor streamer towed by a vessel in a body of water includes determining geodetic positions of a plurality of locations along a first geophysical sensor streamer towed at a first depth in the body of water. A lateral offset is caused between the first geophysical sensor streamer and a second geophysical sensor streamer towed at a second depth in the body of water. A distance is measured between at least two selected points along the first geophysical sensor streamer and a selected point along the second geophysical sensor streamer. A depth is measured at at least one point along the second geophysical sensor streamer. A geodetic position is determined at a selected point along the second geophysical sensor using the depth measurement, a direction of the lateral offset and the measured distances.

Abstract: A marine electromagnetic sensor cable system includes a first sensor cable subsystem including at least a first sensor cable segment. The first sensor cable segment includes a plurality of spaced apart electrodes which electrically contact a body of water when the first sensor cable segment is immersed therein, and an electrical conductor coupled to each electrode, each electrical conductor extending from one longitudinal end of the sensor cable segment to the other. The system includes a first signal processing module electrically coupled to a longitudinal end of the first sensor cable segment, and including a voltage measuring circuit electrically connected between two or more electrodes from the first plurality of electrodes. Marine electromagnetic surveys are conducted using the marine electromagnetic sensor cable system.

Abstract: A sensor streamer stretch section includes at least one spring. A means for coupling the spring at each end to at least one of a sensor streamer and a lead in cable is included. A cable is coupled at its ends to the means for coupling. The cable is capable of carrying at least one of electrical and optical signals. The cable is formed such that the cable undergoes substantially no axial strain when the shock cord is elongated. An adjustable damper is coupled between the means for coupling at each end of the stretch section.

Abstract: A method for determining a longitudinal position of at least one geophysical sensor on a towed marine streamer includes measuring a parameter related to tension at least one position along the streamer. A change in length of the streamer is determined using the measured parameter. The longitudinal position of the at least one sensor is determined. A marine streamer includes at least one geophysical sensor and at least one tension sensor capable of measuring a parameter related to axial tension.

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 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: The geodetic position of a point on a streamer towed by a vessel in a body of water may be determined. Geodetic positions of a plurality positions along at least two of a plurality streamers towed in the body of water may be determined. Positions may be selected from the plurality of positions. Distances between pairs of the selected positions and between each of the selected positions and the point may be determined. Geodetic position of the point may be determined using the geodetic positions and distances.

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 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: A method for determining a longitudinal position of at least one geophysical sensor on a towed marine streamer includes measuring a parameter related to tension at least one position along the streamer. A change in length of the streamer is determined using the measured parameter. The longitudinal position of the at least one sensor is determined. A marine streamer includes at least one geophysical sensor and at least one tension sensor capable of measuring a parameter related to axial tension.

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 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.