Abstract: Techniques are disclosed relating to calibrating sensors configured to measure both pressure and acceleration. In various embodiments, a system detects a first voltage produce by a first piezoelectric material in a hydrophone when the hydrophone is exposed to an acceleration and detects a second voltage produced by a second piezoelectric material in the hydrophone when the hydrophone is exposed to the acceleration. The system, in some embodiments, compares the first voltage and the second voltage. Based on the comparing of the first and second voltages, in some embodiments, the system determines a resistance for a variable resistor coupled to one of the first and second piezoelectric materials.

Abstract: Calibration based on twist and orientation for towed object can include determining an amount of twist as a function of length of a portion of a towed object based on output of tilt sensors in the portion of the towed object and a model that describes the twist along the portion of the towed object. An orientation of a seismic sensor can be determined based on the determined amount of twist and a position of the seismic sensor along a length of the portion of the towed object. The seismic sensor can be calibrated based on the orientation.

Abstract: Geophysical survey methods. At least some of the example embodiments are methods of performing a marine geophysical survey including: towing a plurality of sensor streamers behind a tow vessel, each sensor streamer coupled to the tow vessel by a respective lead-in cable; towing, by the tow vessel, a plurality of lead vessels with each lead vessel pulling a respective seismic source, each lead vessel pulled by a respective tow cable and at least one intermediate cable; actuating the respective seismic sources pulled by the plurality of lead vessels; and gathering seismic data by each of the sensor streamers.

Abstract: A marine vibrator may include a containment housing, a sound radiating surface, and a compliance chamber. The compliance chamber may include a compliance chamber housing, a non-linear linkage assembly, and a low pressure chamber. The compliance chamber housing may define at least a portion of a compliance chamber internal volume having a compliance chamber internal gas pressure. The low pressure chamber may comprise a low pressure piston and a low pressure chamber housing. The low pressure chamber housing may define at least a portion of a low pressure chamber internal volume having a low pressure chamber internal gas pressure. The low pressure piston may be configured to move in response to a pressure differential across the low pressure piston such that a resonance frequency of the marine vibrator may be changed.

Abstract: Processes and systems for deblending blended seismic data with attenuated source signatures and source ghost are described. Processes and systems compute blended upgoing pressure wavefield based on blended pressure wavefield and blended vertical velocity wavefield recorded in a marine survey of a subterranean formation. Downgoing vertical velocity wavefield is computed based on near-field pressure wavefields generated by source elements of sources activated in the marine survey. Deblended wavefield is computed based on the blended upgoing pressure wavefield and the downgoing vertical velocity source wavefield. The deblended wavefield may be used to generate an image of the subterranean formation with the source signatures and source ghosts contained in the blended pressure wavefield and blended vertical velocity wavefield.

Abstract: Deploying and retrieving streamer cleaning devices. At least some of the example embodiments are methods including transferring a streamer cleaning device to a geophysical sensor streamer. The transferring may include towing the geophysical sensor streamer through water while the geophysical sensor streamer submerged, towing a tow fish through water by way of an umbilical (the streamer cleaning device coupled within a payload area of the tow fish during the towing of the tow fish through the water), landing the tow fish on the geophysical sensor streamer and thereby abutting the streamer cleaning device against the geophysical sensor streamer, closing the streamer cleaning device around the geophysical sensor streamer, releasing the streamer cleaning device from the payload area, and separating the tow fish from streamer cleaning device and the geophysical sensor streamer.

Abstract: Techniques are disclosed relating to control of seismic sources such as marine vibrators. According to some embodiments, iterative learning control (ILC) systems may be used to control such seismic sources. According to some embodiments, local sensor(s) placed in, on, or near a seismic source and/or remote sensors placed in the far-field region may be used to determine a transfer function for the seismic source for such ILC control. A sensor is configured to measure the acoustic output of the marine vibrator along with signal pulses from at least one impulsive seismic signal source. The ILC is disabled when it is determined that the impulsive seismic is active based on the sensor measurements.

Abstract: Roll data can be acquired from a magnetometer and an accelerometer of a towed object telemetry unit coupled to a towed object during rolls of the towed object in two or more different headings. The magnetometer can be calibrated based on the roll data. Turn data can be acquired from the magnetometer and the accelerometer during a turn of the towed object from a first heading to a second heading. The magnetometer can be further calibrated based on the turn data.

Abstract: Inversion of enhanced-sensitivity controlled source electromagnetic data can include combining measured controlled source electromagnetic (CSEM) data onto a common set of virtual receiver positions for each of a plurality of positions of a source along a survey path, determining a steering vector that enhances a sensitivity of the measured CSEM data to a subsurface resistivity variation, and performing an inversion using the measured CSEM data and modeled CSEM data, each having the steering vector applied thereto as a data weight, to better identify the subsurface resistivity variation.

Abstract: Processes and systems for deblending blended seismic data with attenuated source signatures and free-surface effects are described. The blended seismic data may have been recorded in a marine survey in which multiple sources are activated in the body of water above a subterranean formation. Receivers record overlapping pressure and vertical velocity wavefield responses from the subterranean formation as corresponding blended pressure wavefield and blended vertical velocity wavefield. Processes and systems compute an upgoing pressure wavefield and a downgoing vertical velocity wavefield based on the blended pressure wavefield and blended vertical velocity wavefield. Deblended primary pressure wavefields are computed based on the upgoing pressure and downgoing vertical velocity. The deblended primary pressure wavefields may be used to generate images of the subterranean formation that are substantially free of source signatures and free-surface effects.

Abstract: Managing movement of data packets along a geophysical sensor cable. At least some embodiments include a geophysical sensor cable section having an internal volume within which geophysical sensors are disposed at spaced apart locations. A digitizer is disposed within the internal volume and is communicatively coupled to sensors. A telemetry unit within the internal volume is communicatively coupled to the digitizer. The telemetry unit may comprise multiple forward ports, multiple aft ports and a controller communicatively coupled to the forward ports, the aft ports, and the digitizer. The controller may be configured to: relay downstream-directed packets received on an active forward port through all aft ports; gather sensor data from the digitizer and send the sensor data as upstream-directed packets through the active forward port; and relay any upstream-directed packets received on aft ports through the active forward port.

Abstract: A method for seismic data processing can include obtaining seismic data acquired based upon trigger times and not based upon positions of triggered source elements. The seismic data can include near-continuously recorded seismic data in split records. The split records can be spliced together into a single near-continuous record to produce a trace with seismic data from a single acquired line. The seismic data can be processed by performing a spatial shift for each of a number of time samples to correct for motion of a number of seismic receivers.

Abstract: This disclosure describes processes and systems for generating a seismic image of a subterranean formation from recorded seismic data gathers obtained in a marine seismic survey of the subterranean formation. The seismic data comprises recorded pressure and vertical velocity wavefields that are used to separate the recorded pressure wavefield into upgoing and downgoing pressure wavefields. A seismic image is computed from the subterranean formation based on a product of the downgoing pressure wavefield and a migration operator applied to the upgoing pressure wavefield. The downgoing pressure wavefield is a boundary source wavefield and the upgoing pressure wavefield is boundary receiver wavefield of the migration operator. The seismic image is iteratively updated by computing a residual seismic image based on the upgoing pressure wavefield and adding the residual seismic image to the seismic image.

Abstract: Techniques are disclosed relating to reducing noise in geophysical marine survey data. Such techniques may include adapting an initial set of noise templates to recorded seismic data to generate adapted noise templates and estimating a noise component in the recorded seismic data. The estimating may include determining a degree to which noise and signal components are correlated in the recorded seismic data and masking the recorded seismic data proportionally to the degree of correlation. The adapted noise templates may then be further adapted to a difference between the estimate of the noise component and the noise templates themselves. Resultant noise templates may then be applied to denoise the recorded seismic data.

Abstract: Disclosed are advantageous designs for highly-sparse seabed acquisition for imaging geological structure and/or monitoring reservoir production using sea surface reflections. The highly-sparse geometry designs may be adapted for imaging techniques using the primary and higher orders of sea surface reflection and may advantageously allow for the use of significantly fewer sensors than conventional seabed acquisition. The highly-sparse geometry designs may be relevant to 3D imaging, as well as 4D (“time-lapse”) imaging (where the fourth dimension is time). In accordance with embodiments of the invention, geophysical sensors may be arranged on a seabed to form an array of cells. Each cell in the array may have an interior region that contains no geophysical sensors and may be sufficiently large in area such that a 500 meter diameter circle may be inscribed therein.

Abstract: A seismic streamer includes an outer sheath that forms an interior region of the seismic streamer of which a portion is filled with a gel or liquid. The streamer also includes at least one stress member placed off-center in the interior region, and multiple sensors mounted proximate to a center of the interior region, where the sensors include a pressure sensor and a motion sensor. The streamer further includes multiple tilt sensors mounted along the interior region. A method of manufacturing a seismic streamer includes placing at least one stress member off-center along a first direction, mounting multiple spacers along the stress member, and affixing sensors to respective spacers, where the sensors include a pressure sensor and a motion sensor. The method further includes mounting tilt sensors along the first direction and affixing an outer sheath to the streamer that forms an interior region of the seismic streamer.

Abstract: Deploying and retrieving streamer cleaning devices. At least some of the example embodiments are methods including transferring a streamer cleaning device to a geophysical sensor streamer. The transferring may include towing the geophysical sensor streamer through water while the geophysical sensor streamer submerged, towing a tow fish through water by way of an umbilical (the streamer cleaning device coupled within a payload area of the tow fish during the towing of the tow fish through the water), landing the tow fish on the geophysical sensor streamer and thereby abutting the streamer cleaning device against the geophysical sensor streamer, closing the streamer cleaning device around the geophysical sensor streamer, releasing the streamer cleaning device from the payload area, and separating the tow fish from streamer cleaning device and the geophysical sensor streamer.

Abstract: Embodiments relate generally to marine geophysical surveying. More particularly, embodiments relate to an underwater application system for application of a streamer coating to a surface of a streamer. An embodiment may comprise a marine geophysical survey system. The marine geophysical survey system may comprise a streamer and an underwater application system operable to apply a streamer coating to the streamer as the underwater application system travels axially along the streamer.

Abstract: Marine survey data can be acquired at a tow line. The tow line is designed to be coupled between a marine survey vessel and a towed object. A receiver is associated with the tow line and designed to receive marine survey data at a location of the tow line. The receiver can be an optical fiber or other type of receiver.

Abstract: Roll data can be acquired from a magnetometer and an accelerometer of a towed object telemetry unit coupled to a towed object during rolls of the towed object in two or more different headings. The magnetometer can be calibrated based on the roll data. Turn data can be acquired from the magnetometer and the accelerometer during a turn of the towed object from a first heading to a second heading. The magnetometer can be further calibrated based on the turn data.