A method and apparatus for marine surveying. A system includes: a standard-volume source element; a large-volume source element comprising an airgun having a volume greater than 1200 cubic inches; and a long-offset survey streamer. A method includes: towing a standard-volume source element; and towing a large-volume source element; activating the large-volume source element at large shotpoint intervals; and activating the standard-volume source element at standard shotpoint intervals, wherein the large shotpoint intervals are at least twice as long as the standard shotpoint intervals. A method includes: obtaining geophysical data for a subterranean formation; and processing the geophysical data to produce an image of the subterranean formation. A method includes: obtaining a firing plan for a plurality of seismic sources, wherein: a first seismic source of the plurality comprises a large-volume source element, and a second seismic source of the plurality consists of standard-volume source elements.

So-called “Popcorn shooting”, and especially continuous Popcorn shooting, combined with simultaneous source shooting allows considerable flexibility in producing high-resolution data and in creating source arrays. Using a combination of simultaneous source de-blending and Popcorn reconstruction it is possible to construct using post acquisition processing arrays of any desired length by constructing a popcorn pattern that takes into account the vessel speed and physical arrangement of guns behind the towing vessel.

Presented are methods and systems for collecting marine seismic data. The collected seismic data can be low frequency (e.g., less than 10 Hz) or it can be a full seismic bandwidth (1-200 Hz) depending on if the low frequency tuned sources and tuned receivers are combined with conventional sources and receivers. The low frequency sources can be towed or they can be autonomous and positioned in the survey area by tether, drifting or self-propelled. The tuned low frequency receivers are towed at a depth greater than conventional receivers and the sources can be fired independently or simultaneously.

A marine seismic source includes source elements configured to emit waves having different frequencies while the source elements are towed at different predetermined depths, respectively. The predetermined depths are calculated such that water-surface reflections of the waves generated by a source element among the source elements interfere constructively with the waves generated by the source element and propagating toward an explored structure under the seafloor. The waves combine to yield a spike-like signature of the source.

Methods for seismic exploration of a subsurface formation increase productivity by simultaneously actuating closely located vibratory sources. Individual vibrations generated by different sources actuated simultaneously are encoded to enable separation of seismic data corresponding to each of the individual vibrations.

Systems and methods for cement evaluation by determining a shear velocity of a shear wave (26) propagating within a medium (20) located between a formation (12) and a casing (13) in a borehole (11) are presented. The method can include positioning an ultrasonic transducer array (21) in the borehole inside the casing. The method can also include in a pushing mode, generating a shear wave in the medium with the ultrasonic transducer array inside the casing. The method can also include in an interrogation mode, measuring a shear velocity of the shear wave in the medium with the ultrasonic transducer array. The shear velocity may be used to determine whether the medium is solid or liquid.

A method is provided for managing a master vessel change in a multi-vessel seismic system. The system includes a master vessel M and at least one slave vessel. The method includes, during at least a part of a multi-vessel operation: selecting a new master vessel M′ among the at least one slave vessel, triggered by at least one predetermined event; and transmitting, to the at least one slave vessel, at least one piece of information related to a master vessel change from the master vessel M, called old master vessel, to the new master vessel M′.

Computing device, computer software and methods for generating sweep signals corresponding to plural sources that generate seismic waves. The method includes selecting a nominal sweep signal (S0); applying a perturbation (P) to the nominal sweep signal (S0); and calculating the sweep signals (Sn) by varying the perturbation (P), each sweep signal corresponding to a seismic source.

Deblending and deghosting seismic data may include processing blended seismic data acquired after actuation of a first seismic source located at a first depth and a second seismic source located at a second depth. The processing may comprise deblending and deghosting the blended seismic data based on a difference in ghost responses of the first seismic source and the second seismic source.

A subaqueous underground survey system using a reflection seismic survey method includes: multiple sound sources 1 for generating sound waves in the water; a controller 2 for controlling phases of the sound waves; a geophone 3 for receiving reflected waves of the sound waves; and an observation ship 4 equipped with the sound sources 1, wherein the controller 2 controls phases of the sound sources 1 so that the sound waves generated from the respective sound sources 1 have a phase difference at a water bottom surface B, thereby controlling generation of shear waves to propagate into the ground.