Abstract: An actuation location for actuation of a first source coupled to a first marine survey vessel relative to a position of a second marine survey vessel towing a receiver to enhance illumination of a subsurface location can be determined based on a survey route of the second marine survey vessel and a priori data of the subsurface location. The first marine survey vessel can be navigated along a survey route of the first marine survey vessel to the actuation location during a marine survey by changing at least a cross-line position or an in-line position of the first marine survey vessel relative to the survey route of the second marine survey vessel.

Abstract: Implementations for monitoring seismic data recorded in a marine survey of a subterranean formation for coverage gaps are described herein. Implementations include computing Fresnel sum operators for Fresnel zones of the subterranean formation based on a Kirchhoff migration impulse response at horizons of a representative plane layer model of a survey area of the subterranean formation. Implementations also include computing an acceptability map of the survey area based on the Fresnel sum operators. The acceptability map reveals coverage gaps in the survey area. Geoscientist may use the acceptability map to infill seismic data in areas of the survey area that correspond to the coverage gaps.

Abstract: A plurality of sensors and a controller are disposed in a marine seismic streamer. Each of the sensors comprises an enclosure having two opposing interior walls, first and second piezoelectric elements disposed on the opposing interior walls, a third piezoelectric element disposed on a flexible substrate within the enclosure between the opposing interior walls, a pressure signal output node and an acceleration signal output node disposed on the exterior surface of the enclosure. A combined pressure signal derived from the pressure signal output nodes of the plural sensors is coupled to a pressure signal input of the controller. A combined acceleration signal derived from the acceleration signal output nodes of the plural sensors is coupled to an acceleration signal input of the controller. The streamer may be towed, and the combined pressure and acceleration signals may be recorded in a computer-readable medium.

Abstract: A system for ocean bottom node (OBN) deployment can include a first deployment device located on a marine vessel, a second deployment device located on the marine vessel, a first line coupled to the first deployment device and comprising a first plurality of OBNs, and a second line coupled to the second deployment device and comprising a second plurality of OBNs. The first deployment device and the second deployment device can be configured to deploy and retract the first line and the second line simultaneously.

Abstract: This disclosure presents processes and systems for generating an image of a subterranean formation from seismic data recorded in a seismic survey of the subterranean formation. The seismic data is contaminated with low frequency noise in a low frequency band. Processes and systems reconstruct seismic data in the low frequency band of the seismic data to obtain low frequency reconstructed seismic data that is free of the low frequency noise. The low frequency reconstructed seismic data is used to construct a velocity model of the subterranean formation. The velocity model and the low frequency reconstructed seismic data are used to generate an image of the subterranean formation that reveals structures of the subterranean formation without contamination from the low frequency noise.

Abstract: Methods and apparatus are described for using ambient acoustic energy as a passive source in marine seismic surveys. An example embodiment includes (a) accessing signals that were recorded by sensors in the presence of acoustic energy that was emitted by a passive source during a marine seismic survey; (b) identifying a point to represent a location from which the acoustic energy was emitted; (c) isolating, from the recorded signals, a direct wavefield arriving at the sensors from a direction of the identified point; and (d) generating an estimated passive source wavefield at the identified point by backpropagating the isolated direct wavefield to the identified point. The estimated passive source wavefield may be used, together with signals recorded by the sensors, to generate an image of a subsurface earth volume without the use of active seismic sources.

Abstract: Apparatus and techniques are disclosed relating to a two-axis sensing element. In various embodiments, a two-axis sensing element includes a mounting plate that includes a first pair of mounting slots oriented in a first direction and a second pair of mounting slots oriented in a second, different direction. Further, in various embodiments, the two-axis sensing element may include a first pair of bender elements and a second pair of bender elements. The first pair of bender elements may be mounted through the first pair of mounting slots such that the first pair of bender elements is oriented in the first direction and the second pair of bender elements may be mounted through the second pair of mounting slots such that the second pair of bender elements is oriented in the second, different direction. In various embodiments, the mounting plate may transect each of the bender elements into two cantilever portions.

Abstract: A method for a marine seismic survey can include towing streamers that are spaced apart in a cross-line direction by a streamer separation (L) and towing seismic source elements that are spaced apart in the cross-line direction by a source separation based on an integer (k), an inverse of a quantity of the seismic source elements (1/S), and the streamer separation as represented by (k+1/S)L. The seismic source elements can be actuated and seismic signals can be detected at each of a plurality of receivers on the streamers.

Abstract: Techniques are disclosed relating to performing marine surveys with non-uniform spacing of survey elements in a cross-line direction. This may include, for example, performing a survey pass in a multi-pass survey by towing a plurality of sources and sensors in a towing pattern with non-uniform spacing between adjacent ones of the sources. In some embodiments, the non-uniform spacing between adjacent ones of the sources is determined based on a common mid-point (CMP) spacing parameter for the survey pass in the cross-line direction. The spacing parameter may relate, for example, to difference in average CMP spacing for different parts of the survey spread, variance in CMP spacing, and/or width of the survey spread for which a threshold CMP spacing distance is satisfied. In various embodiments, the disclosed techniques may improve survey resolution and/or accuracy and may require a smaller number of survey passes and/or a reduced amount of survey equipment relative to traditional techniques.

Abstract: Numerous techniques and apparatus are disclosed relating to the performance of 4D marine geophysical surveys over at least first and second areas covered, respectively, by first and second preexisting baseline surveys. Performing the monitor surveys may include deploying a monitor survey streamer layout that can be used to repeat streamer positions of both the first and the second preexisting baseline surveys, and using the monitor survey streamer layout to perform the monitor survey over the first and second areas in a manner that repeats all streamer positions of the first preexisting baseline survey when over the first area, and that repeats all streamer positions of the second preexisting baseline survey when over the second area. Streamer layouts corresponding to the first and second preexisting baseline surveys may differ in at least one of the following characteristics: streamer separation or total number of streamers.

Abstract: Techniques are disclosed for reducing noise when computing time-lapse differences between two or more geophysical surveys performed over the same region. In some computer-implemented embodiments, a time-lapse difference is determined between first and second data representing the first and second surveys, respectively. Based on geometry information corresponding to the second survey, first estimated data is generated representing how the first data would have looked if the second survey geometry had been used during the first survey. A noise model is generated based on differences between the first data and the first estimated data. The time-lapse difference is then adjusted using the noise model, thereby reducing noise in the time-lapse difference caused by differences between the geometries of the first and second surveys.

Abstract: Processes and systems for generating images of a subterranean formation from recorded seismic data obtained in a marine survey are described. Processes and systems compute reverse-time receiver-motion-corrected upgoing and downgoing pressure wavefields at different locations of corresponding upgoing and downgoing observation levels based on the recorded seismic data. The reverse-time receiver-motion-corrected upgoing and downgoing pressure wavefields are time forwarded and extrapolated to obtain a corresponding receiver-motion-corrected upgoing and downgoing pressure wavefields at locations of a static observation level. An image of the subterranean formation is generated based at least in part on the receiver-motion-corrected upgoing pressure wavefield and the receiver-motion-corrected downgoing pressure wavefield.

Abstract: An example autonomous marine survey node can include a circuitry component including circuitry of a marine survey receiver, a ballast tank coupled to the circuitry component, and a maneuvering system coupled to the circuitry component. The ballast tank can be configured to adjust a buoyancy of the autonomous marine survey node. The maneuvering system can be configured to autonomously perform aerial maneuvers and autonomously perform submersed maneuvers near an underwater surface.

Abstract: This disclosure describes processes and systems for generating a high-resolution velocity model of a subterranean formation from recorded seismic data gathers obtained in a marine seismic survey of the subterranean formation. A velocity model is computed by iterative FWI using reflections, resolving the velocity field of deep subterranean targets without requiring ultralong offsets. The processes and systems use of an impedance sensitivity kernel to characterize reflections in a modeled wavefield, and then use the reflections to compute a velocity sensitivity kernel that is used to produce low-wavenumber updates to the velocity model. The iterative process is applied in a cascade such that position of reflectors and background velocity are simultaneously updated. Once the low-wavenumber components of the velocity model are updated, the velocity model is used as an input of conventional FWI to introduce missing velocity components (i.e., high-wavenumber) to increase the resolution of the velocity model.

Abstract: Apparatus and techniques are disclosed relating to towing marine equipment. In some embodiments, a vessel tows equipment through a body of water using a towing member with an associated fairing that includes a slit, such that an axis of the slit is non-perpendicular to a portion of the towing member from which the fairing extends.

Abstract: Apparatus and techniques are disclosed relating to sensor housing and spacer carrier assemblies. In various embodiments, a spacer carrier provides a cavity through a body of the spacer carrier and a first alignment element positioned at a first end of the cavity. In some embodiments, a sensor housing is configured to be deployed within the cavity through the body of the spacer carrier. The sensor housing may include a housing body configured to receive a sensor and a second alignment element configured to interface with the first alignment element. In various embodiments, the first and second alignment elements are configured to maintain an orientation of the sensor housing within the cavity when the sensor housing is inserted into the spacer carrier.

Abstract: Computational systems and methods for randomizing the order in which multiple sources are fired in simultaneous source acquisition are described. In one aspect, pseudo-randomly shifted time delays are generated for each shot interval of a marine-survey-time line. Each shifted time delay is assigned to one or the sources. The sources within each shot interval are fired based on the shifted time delays.

Abstract: A class of electrical connectors are described along with methods of manufacturing the same. In one example embodiment, a method of assembling a connector includes extending a twisted pair through a slot in a seal plate; untwisting the twisted pair along a first distance; inserting first and second conductors of the twisted pair through first and second through holes of a seal carrier; coupling first and second electrical terminals to the first and second conductors; re-twisting the twisted pair along a portion of the first distance by rotating the seal carrier; and inserting the seal carrier into the slot of the seal plate.

Abstract: Systems and methods for attenuating residual acoustic energy in marine seismic data are disclosed. In one aspect, a number of gathers are recorded for consecutive activations of a marine source. Each recorded gather contains a record of acoustic reflections from a subterranean formation after activation of the source and residual acoustic energy from one or more previous activations of the source. The gathers are aligned to generate aligned gathers with the residual acoustic energy coherent between the aligned gathers and the reflections incoherent between the aligned gathers. A set of model gathers of the residual acoustic energy is generated from the aligned gathers. The model gathers are subtracted from one or more of the corresponding recorded gathers to generate one or more gathers with attenuated residual acoustic energy.

Abstract: Methods and systems to separate seismic data associated with impulsive and non-impulsive sources are described. The impulsive and non-impulsive sources may be towed through a body of water by separate survey vessels. Receivers of one or more streamers towed through the body of water above a subterranean formation generate seismic data that represents a reflected wavefield produced by the subterranean formation in response to separate source wavefields generated by simultaneous activation of the impulsive source and the non-impulsive source. Methods and systems include separating the seismic data into impulsive source seismic data associated with the impulsive source and non-impulsive source seismic data associated with the non-impulsive.