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.

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 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 method for marine electromagnetic surveying includes transmitting a first electromagnetic field oriented in a first direction into a body of water. A second electromagnetic field oriented in a second direction is transmitted into the body of water, wherein the second direction is substantially transverse to the first direction. A parameter related to electromagnetic field amplitude is detected at a plurality of longitudinally and laterally spaced apart positions behind a vessel. The components of the detected electromagnetic field parameter are resolved into components along the first and second directions by using the geometrical symmetries and asymmetries of the transmitting source. Systems for implementing such methods are also provided.

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: 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.