Abstract: A marine seismic survey comprises towing a first source and a first streamer spread having a length L behind a first vessel. Sensors in the streamer spread record signals from the first source over a range of offset distances X to X+L. A second source is towed behind a second vessel that does not tow a streamer spread. Sensors in the streamer spread record signals from the second source over a range of offset distances A+L to A+2L. Sensors in the streamer spread do not record signals over a range of offset distances X+L to A+L from any active seismic sources used in the marine seismic survey.

Abstract: Techniques are disclosed relating to acquisition and imaging for marine surveys. In some embodiments, a transition survey that uses both one or more sources of a first type (e.g., impulsive sources) and one or more sources of a second type (e.g., vibratory sources) may facilitate calibration of prior surveys that use the first type of sources with subsequent surveys that use the second type of source. In some embodiments, the different types of sources may be operated simultaneously at approximately the same location. In some embodiments, signals generated by the sources are separated, e.g., using deconvolution. The signals may then be compared to generate difference information, which in turn may be used to adjust sensor measurements from a previous or subsequent survey. In various embodiments, the disclosed techniques may improve accuracy in images of geological formations and may facilitate transitions to new types of seismic sources while maintaining continuity in 4D surveys.

Abstract: Techniques and apparatus are disclosed for performing marine seismic surveys. In some embodiments, one or more vessels are used to tow a set of streamers and two or more sources such that a first set of sources consists of all those that are disposed within a first threshold distance from the streamers, and a second set of sources consists of all those that are disposed beyond a second, greater, threshold distance from the streamers. Sources in the first set are activated more frequently than sources in the second set are activated.

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: Techniques are disclosed relating to marine geophysical surveys. Various output characteristics of a vibratory source may be modified based on whether a source is targeting an identified portion of a survey area. The portion of the survey area may be detected during the survey or may be pre-identified. In some embodiments, a survey system drives a vibratory source using digital codes having different lengths based on whether the source is targeting an identified portion of a survey area. The disclosed techniques may improve imaging of geology under certain types of formations or may reduce environmental impact, in various embodiments.

Abstract: Techniques are described for utilizing far offset impulsive source activations in various contexts, including when performing marine seismic surveys, when manufacturing a geophysical data product in conjunction with such surveys, or when generating an image of geological features of a subsurface. According to some embodiments, near offset impulsive source activations are caused in a body of water at each of a plurality of near offset shot points, and composite far offset impulsive source activations are caused in the body of water at each of a plurality of far offset shot points. Each of the composite far offset impulsive source activations comprises a succession of component impulsive source activations occurring over a far offset shot length. The far offset shot length is short enough to satisfy a stationary source assumption for frequencies at or below a maximum frequency of interest for the far offset shot points.

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 method and apparatus for operating a single source vessel along a survey path, the source vessel towing a source and a first plurality of streamers; operating a streamer vessel along the survey path, the streamer vessel towing a second plurality of streamers; actuating the source; acquiring near-offset data with a first plurality of receivers; and acquiring long-offset data with a second plurality of receivers. A system includes a source vessel coupled to: a source; and a near-offset survey spread; a streamer vessel coupled to a long-offset survey spread, wherein a streamer spacing density of the long-offset survey spread is no greater than a streamer spacing density of the near-offset survey spread; and a survey plan including navigation information for the source vessel and the streamer vessel, wherein the navigation information directs the source vessel and the streamer vessel along a common survey path while the source is actuated.

Abstract: Systems and computer readable media are described that actuate at least one marine seismic source according to a constrained sequence. The sequence exhibits an actuation time or distance interval between each actuation. The actuation time or distance interval corresponds to the sum of a nominal time or distance and a respective dither time or dither distance for each actuation. The sequence is constrained such that differences between consecutive dither times or dither distances remain within a threshold dither difference. Constraining the sequence according to the threshold dither difference enables increased bottom speeds for the source (i.e., increased speeds of the source relative to the seafloor), while still maintaining at least a minimum actuation time or distance interval for the source, taking into account both the nominal time or distance and the respective dither times or dither differences.

Abstract: Techniques are described for utilizing far offset impulsive source activations in various contexts, including when performing marine seismic surveys, when manufacturing a geophysical data product in conjunction with such surveys, or when generating an image of geological features of a subsurface. According to some embodiments, near offset impulsive source activations are caused in a body of water at each of a plurality of near offset shot points, and composite far offset impulsive source activations are caused in the body of water at each of a plurality of far offset shot points. Each of the composite far offset impulsive source activations comprises a succession of component impulsive source activations occurring over a far offset shot length. The far offset shot length is short enough to satisfy a stationary source assumption for frequencies at or below a maximum frequency of interest for the far offset shot points.

Abstract: Techniques are disclosed relating to geophysical surveying. In various embodiments, a computer system may access seismic data for a geological formation, where the seismic data is recorded, using one or more sensors, during a seismic survey in which a first vibratory source was driven using a first digital code for at least a first time interval. The first digital code, in some embodiments, may include a first plurality of subsections corresponding to portions of the first time interval. In some embodiments, the computer system may image a first location of the geological formation using a correlation of only a first sub-section of the first plurality of sub-sections with the seismic data. Further, in some embodiments, the computer system may image a second location of the geological formation using a correlation of two or more of the first plurality of sub-sections with the seismic data.

Abstract: Techniques are disclosed relating to geophysical surveying. In various embodiments, a marine survey vessel may tow a plurality of streamers that each include a plurality of seismic sensors. Further, the survey vessel may tow a plurality of vibratory sources. In various embodiments, a first sweep may be performed, using one or more of the plurality of vibratory sources, for a first time interval. Further, in various embodiments, disclosed techniques may include recording, during the first time interval using the plurality of seismic sensors, seismic data on a tangible, computer-readable medium, thereby creating a geophysical data product.

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.

Abstract: Techniques are disclosed relating to geophysical surveying. In some embodiments, a marine survey vessel tows multiple sensor streamers in addition to vibratory sources deployed relative to the sensor streamers. In some embodiments, the vessel tows vibratory sources emitting energy within different frequency bands in different deployment zones. In some embodiments, one or more sources are driven with different sweep functions, different activation patterns, and/or different sweep lengths. Various disclosed techniques for manufacturing a geophysical data product may potentially simplify equipment used for towing sources, reduce survey complexity without reducing resolution, increase resolution without increasing survey complexity, improve energy content recovered from deep reflections, and/or reduce the environmental impact of emitting seismic energy.

Abstract: Techniques and apparatus are disclosed for performing marine seismic surveys. In some embodiments, one or more vessels are used to tow a set of streamers and two or more sources such that a first set of sources consists of all those that are disposed within a first threshold distance from the streamers, and a second set of sources consists of all those that are disposed beyond a second, greater, threshold distance from the streamers. Sources in the first set are activated more frequently than sources in the second set are activated.

Abstract: Techniques are disclosed relating to marine geophysical surveys. Various output characteristics of a vibratory source may be modified based on whether a source is targeting an identified portion of a survey area. The portion of the survey area may be detected during the survey or may be pre-identified. In some embodiments, a survey system drives a vibratory source using digital codes having different lengths based on whether the source is targeting an identified portion of a survey area. The disclosed techniques may improve imaging of geology under certain types of formations or may reduce environmental impact, in various embodiments.

Abstract: Techniques are disclosed relating to configuring a marine seismic survey. In some embodiments, a vessel may be coupled to one or more seismic sources and one or more seismic streamers, and a second vessel may be coupled to one or more far offset seismic sources. The near offset sources may be configured to actuate according to a shot point interval; the far offset sources may be configured to actuate according to a longer shot point interval. In some embodiments, the longer shot point interval may be a multiple of the near offset source shot point interval. Determining the first and second shot point intervals may be based in part on, for example, the wave frequencies of the far offset sources, the requirements of a full wave inversion process, or various configurational parameters of seismic surveys.

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 for constraining a dither time can comprise a source and a controller coupled to the source. The controller can be configured to actuate the source in sequence, while the source is moving through a fluid volume at a bottom speed, with an actuation time interval between each actuation comprising a sum of a nominal time and a dither time for each actuation and constrain the dither time for each actuation such that a reduction of the actuation time interval relative to a directly precedent actuation time interval is at most a threshold dither time difference, wherein the threshold dither time difference corresponds to a maximum bottom speed.

Abstract: A system for constraining a dither time can comprise a source and a controller coupled to the source. The controller can be configured to actuate the source in sequence, while the source is moving through a fluid volume at a bottom speed, with an actuation time interval between each actuation comprising a sum of a nominal time and a dither time for each actuation and constrain the dither time for each actuation such that a reduction of the actuation time interval relative to a directly precedent actuation time interval is at most a threshold dither time difference, wherein the threshold dither time difference corresponds to a maximum bottom speed.