Abstract: Methods for performing a marine survey of a subterranean formation using a hybrid combination of ocean bottom seismic (“OBS”) receivers, wide towed sources, and moving streamers are described herein. In one aspect, a sail line separation in a crossline direction is determined based on an average streamer separation and number of streamers. An array of OBS receivers are deposited on a surface of a subterranean formation with an OBS receiver separation that is based on the sail line separation. Wide towed sources and streamers are towed above the array of OBS receivers behind a survey vessel that travels sail lines separated by the sail line separation. The wide towed sources may be activated above the array of OBS receivers. Wavefields reflected from the subterranean formation are recorded at the OBS receivers and receivers located in the streamers as seismic data.

Abstract: A system and method controls impulsive source activations in a blended acquisition marine seismic survey. A component of the system generates a sequence of dither values deterministically and stores the sequence of dither values, or source activation indicators derived therefrom, in a non-transitory medium readable by a control system operable to execute shot points during the survey responsive to the values stored in the medium. According to some embodiments, generating the dither values comprises iteratively selecting from a fixed set of candidate dither values to produce a candidate sequence of dither values. The selecting is based on evaluating one or more quantitative measures of randomness and one or more quantitative measures of separation exhibited by at least a portion of the candidate sequence of dither values. Generated sequences improve deblending results by reducing coherence exhibited by the dither values in the sequences.

Abstract: A marine seismic data acquisition system may include first and second containers deployable in a body of water. The first container includes a first seismic data acquisition channel capable of transducing seismic energy in the body of water having a first maximum amplitude, and the second container includes a second seismic data acquisition channel capable of transducing seismic energy in the body of water having a second maximum amplitude. The first seismic data acquisition channel is associated with at least a first seismic sensor, and the second seismic data acquisition channel is associated with at least a second seismic sensor. The second sensor corresponds to a same sensor type as the first seismic sensor, and the first maximum amplitude is higher than the second maximum amplitude.

Abstract: One embodiment disclosed relates to an array of sensors for towed marine streamers. The array may include a first plurality of transducers of a first form configured to have a first polarity in electrical response to a change in an environmental condition and a second plurality of transducers of a second form coupled to the first plurality of transducers and configured to have a second polarity, opposite of the first polarity, in electrical response to the change in the environmental condition. The first plurality may be equal to the second plurality. The first plurality of transducers may be coupled to the second plurality of transducers in a linearly alternating fashion. The array may be coupled to a amplifier. The array may be included along a length of at least a portion of a marine streamer. Another embodiment disclosed relates to a method of acquiring sensor signals in a marine streamer being towed by a vessel during a seismic marine survey. Other embodiments, aspects and features are also disclosed.

Abstract: A marine seismic data acquisition system may include first and second containers deployable in a body of water. The first container includes a first seismic data acquisition channel capable of transducing seismic energy in the body of water having a first maximum amplitude, and the second container includes a second seismic data acquisition channel capable of transducing seismic energy in the body of water having a second maximum amplitude. The first seismic data acquisition channel is associated with at least a first seismic sensor, and the second seismic data acquisition channel is associated with at least a second seismic sensor. The second sensor corresponds to a same sensor type as the first seismic sensor, and the first maximum amplitude is higher than the second maximum amplitude.

Abstract: A cyclic source group for marine seismic surveying includes a set of three or more impulsive marine seismic sources and at least one controller configured to activate the sources in sequential activation cycles. The activation cycles are such that exactly one nominal shot point occurs for each of the sources in the set during each activation cycle and all nominal shot points within a given activation cycle are distinct. Pairs of sequential nominal shot points within the activation cycle and across sequential activation cycles define respective nominal shot point intervals. At least two of the nominal shot point intervals are unequal, but nominal shot points for each individual source in the set occur at regular intervals.

Abstract: A hydrophone device body is formed by first and second electrically conductive enclosures disposed on opposite sides of an electrically insulative member. Electrically conductive surfaces of the device's positive and negative electrodes on the exterior of the device body are symmetrical about the device body. When placed appropriately in a submersible container, such as along the central longitudinal axis of a seismic streamer or cable, the device is resistant to cross feed noise that couples to its electrodes from outside the streamer or cable.

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: 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: Techniques are disclosed relating to deblending of sources in multi-source geophysical survey data, including marine or land-based data. Multiple sets of deblended receiver traces are generated by iteratively applying a coherency filter to estimated sets of deblended receiver traces and updating a residual until a termination condition is reached. In some embodiments, applying the coherency filter during a current iteration may include determining coefficients of the coherency filter based on estimated sets of deblended receiver traces from an immediately prior iteration. In further embodiments, applying the coherency filter may include applying a 3D projection filter, such as an fxy projection filter.

Abstract: Embodiments relate generally to marine geophysical surveying. More particularly, embodiments relate to a wax application system for application of a wax 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 a wax application system operable to receive the streamer on deployment and apply a wax coating to the streamer as the streamer is being deployed from a survey vessel into a body of water.

Abstract: In survey configurations for towed streamer shallow target investigations, seismic sources are placed in one or more of several zones disposed at different inline offsets relative to the streamers. In some embodiments, a vessel tows a set of one or more streamers along with a set of one or more sources disposed aft of the tail end of the streamers. In other embodiments, a vessel tows a set of one or more streamers, a set of one or more near offset sources disposed forward of the front end of the streamers, and a set of one or more far offset sources disposed forward of the near offset sources.

Abstract: One or more images of subsurface geological features are generated based on recorded seismic data that contain controlled source components and uncontrolled source components blended together. A current recorded dataset is determined from the recorded seismic data, and one or more iterations of a separation procedure are performed on the current recorded dataset to accumulate isolated controlled source components and isolated uncontrolled source components therefrom. The one or more images are generated based on the isolated controlled source components and on the isolated uncontrolled source components.

Abstract: Techniques are disclosed relating to machine learning in the context of noise filters for sensor data, e.g., as produced by geophysical surveys. In some embodiments, one or more filters are applied to sensor data, such a harsh filter determined to cause a threshold level of distortion in measured reflections, a mild filter determined to leave a threshold level of remaining noise signals, or an acceptable filter. In some embodiments, the system trains a machine learning classifier based on outputs of the filtering procedures and uses the classifier to determine whether other filtered sensor data from the same survey exhibits acceptable filtering. This may improve accuracy or performance in detecting unacceptable filtering, in some embodiments.

Abstract: A vessel is configured to tow a marine seismic source, a spread of standard-offset streamers, and a long-offset streamer in a manner such that: a standard streamer maximum offset, measured from the at least one source to an aft-most receiver in the standard-offset streamers, is not more than 20 km; and a long-offset streamer maximum offset, measured between the at least one source and an aft-most receiver in the long-offset streamer, is longer than the standard streamer maximum offset and is between 12 km and 40 km. In some embodiments, the long-offset streamer and the standard-offset streamers are coupled to a same spreader line. In other embodiments, the long-offset streamer is coupled to the vessel by a long-offset lead-in line. In still other embodiments, the standard-offset streamers are coupled to a first spreader line, and the long-offset streamer is coupled to a second spreader line disposed aft of the first spreader line.

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: Methods and apparatus are described for performing a 4D monitor marine seismic survey that repeats a previous survey. A number of sources may be used during the 4D monitor survey that differs from a number of sources that were used during the previous survey. Shot points from the previous survey are repeated by the 4D monitor survey, and additional shot points may be produced during the 4D monitor survey that were not produced during the previous survey. Embodiments enable efficiency and data quality improvements to be captured during 4D survey processes, while preserving repeatability.

Abstract: A system and method controls impulsive source activations in a blended acquisition marine seismic survey. A component of the system generates a sequence of dither values deterministically and stores the sequence of dither values, or source activation indicators derived therefrom, in a non-transitory medium readable by a control system operable to execute shot points during the survey responsive to the values stored in the medium. According to some embodiments, generating the dither values comprises iteratively selecting from a fixed set of candidate dither values to produce a candidate sequence of dither values. The selecting is based on evaluating one or more quantitative measures of randomness and one or more quantitative measures of separation exhibited by at least a portion of the candidate sequence of dither values. Generated sequences improve deblending results by reducing coherence exhibited by the dither values in the sequences.

Abstract: A marine streamer includes: an optical fiber disposed along a length of the streamer; a light source; and light analysis equipment, wherein: the length is at least 20 km, a diameter of the streamer is no more than 25 mm, the optical fiber, light source, and light analysis equipment are configured to provide a receiver sampling density of at least 1 per meter, and the streamer is configured to be towed nominally horizontally through a body of water. A method of marine surveying includes: towing a streamer spread at a first depth of 10 m to 30 m with a survey vessel; and towing Distributed Acoustic Sensing (DAS) streamers at a second depth of greater than 30 m. A method includes: acquiring long-offset data with sensors distributed along the DAS streamers.

Abstract: A long-offset acquisition system includes a source vessel; a signal source coupled to the source vessel; and a long-offset streamer coupled to a survey vessel and including an aft-most receiver, an offset of the aft-most receiver being at least 12 km. A long-offset acquisition method includes towing a signal source with a source vessel; towing a first long-offset streamer with a survey vessel; and acquiring data with receivers of the first long-offset streamer. A long-offset acquisition method includes towing a signal source with a first survey vessel; towing a long-offset streamer with a second survey vessel, the long-offset streamer having a plurality of receivers; actuating the signal source while an offset between the signal source and at least one of the plurality of receivers is at least 15 km; and acquiring data with receivers of the long-offset streamer.