A positioning system (100) for marine seismic surveying, comprising a towing vessel (110), a source array (120) and a receiver array (130) with several streamers (131). Each streamer (131) comprises at least three birds (134) and positioning sensors (134-137) wherein several seismic receivers (132) are placed between each pair of birds (134). The system (100) comprises a dynamic model wherein each streamer (131) is represented by a fitted B-spline curve and each bird (134) is associated with a constant velocity and a constant acceleration; and a Kalman filter using the dynamic model and observations from the positioning sensors (134-137) to provide a geodetic position of each seismic receiver (132) with better accuracy than the dynamic model alone and observations alone within a time interval t equal to or less than a minimum time between shots determined by the source array (120).

The invention provides a system (100) for marine seismic surveying, comprising a towing vessel (110) with a controller, a source array (120) and a receiver array (130) with several streamers (131). The source array (120) comprises n>4 identical subarrays (121) configured as at least (n1) seismic sources S.sub.1, . . . , S.sub.n-1, wherein adjacent subarrays (121) are part of at least two sources S.sub.i, S.sub.j at different times.

Seismic shear-wave survey systems and methods that employ inclined borehole pairs with directional detonations. If the boreholes have substantially equal inclinations in opposite azimuthal directions, the resulting signal traces can be combined to isolate shear wave energy contributions, thereby offering potentially enhanced resolution and reduced-complexity interpretation. The boreholes may be cased to ensure repeatability for, e.g., monitoring of reservoir fracturing, treatments, and/or drainage. The directional charges may be immersed to improve coupling of seismic energy into the formation.

Techniques are disclosed relating to tuned seismic signal source arrays for use in seismic surveying. In various embodiments, a survey vessel deploys a plurality of signal sources, including a first signal source and a second signal source, where the first signal source is positioned at a first distance from a subsurface location in a geological formation and the second signal source is positioned at a second distance from the subsurface location that is less than the first distance. Further, various embodiments include performing a first activation of the first signal source at a first time to generate a first seismic signal, and performing a second activation of the second signal source at a second time to generate a second seismic signal, where a particular activation characteristic of the first and second activations differs based on a differences between the first distance and the second distance.

Techniques are disclosed relating to positioning signal sources in a tuned source array for use in seismic surveying. In various embodiments, a survey vessel deploys a plurality of signal sources distributed in a source array. In some embodiments, the plurality of signal sources includes a first signal source positioned at a first depth in a body of water, and a second signal source positioned at a second, shallower depth in the body of water. Various embodiments include controlling the first and second depths such that the first signal source and the second signal source are positioned at substantially the same distance from a target subsurface location in a geological formation. Further, in various embodiments, the first and second signal sources are activated to generate first and second seismic signals.

Methods and systems for computing notional source signatures from modeled notional signatures and measured near-field signatures are described. Modeled near-field signatures are calculated from the modeled notional signatures. Low weights are assigned to parts of a source pressure wavefield spectrum where signatures are less reliable and higher weights are assigned to parts of the source pressure wavefield spectrum where signatures are more reliable. The part of the spectrum where both sets of signatures are reliable can be used for quality control and for comparing the measured near-field signatures to modeled near-field signatures. When there are uncertainties in the input parameters to the modeling, the input parameters can be scaled to minimize the differences between measured and modeled near-field signatures. Resultant near-field signatures are computed by a weighted summation of the modeled and measured near-field signatures, and notional source signatures are calculated from the resultant near-field signatures.

The present invention relates to a seismic source array for deploying a seismic source array, comprising a housing and a plurality of seismic sources suspending from the housing, each source being configured for generating a pressure pulse signal, wherein the array further comprises a protective structure attached to the housing and defining a protective space near the housing, wherein the seismic sources in a first position relative to the housing suspend from the housing such as to be arranged in the protective space defined by the protective structure, and wherein at least one of the seismic sources suspends from the housing by means of a suspension structure configured for moving the at least one seismic source to a second position relative to the housing, the second position being located outside the protective space.

A method for use in marine seismic surveying includes: towing at least a portion of a marine seismic survey spread; imparting a composite swept seismic signal from the marine seismic survey spread, the composite swept seismic signal including a plurality of randomized subsweeps having different frequencies relative to one another and being emitted in parallel; and receiving a respective return for each of the subsweeps.

A method for determining an optimum spacing of seismic energy sources based on mutual admittance includes deploying a plurality of seismic energy sources along a source line, separated by a selected spacing. Seismic receivers are deployed along a receiver line orthogonal to the source line. Seismic energy is simultaneously transmitted from each of the plurality of seismic energy sources while recording signals from the seismic receivers. The transmitting and recording of signals is repeated for a plurality of different spacings between the energy sources. Seismic energy in the recorded signals is determined in separate time windows selected to represent reflected body wave signal, and source generated ground roll noise, respectively. A signal-to-noise ratio with respect to the spacing of the seismic energy sources is calculated and the optimum spacing between energy sources is selected based on the signal-to-noise ratio.

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.