Multi‐Level airgun array: A simple and effective way to enhance the low frequency content of marine seismic data

Cambois, Guillaume; Long, Andrew; Parkes, Gregg; Lundsten, Terje; Mattsson, Anders; Frømyr, Eivind

doi:10.1190/1.3255140

Cited by 23 publications

(13 citation statements)

References 6 publications

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“…Essentially, the ghost is noise that we have to remove and obtain a true high-resolution source. Perfect deghosting leads to the fl at amplitude spectrum of amplitude 1 (Cambois, 2009) The corresponding spectrum is shown in (c).…”

Section: Evaluation Metricsmentioning

confidence: 97%

“…Smith (1984) presented a three-dimensional airgun source with four different depths to suppress the source ghost. Using the beam-steering approach (Shock, 1950), Cambois et al (2009) studied a multilevel source and presented a case study with two levels to demonstrate the effectiveness of improving the low and high frequencies. A two-level technique was also recently introduced to attenuate the source ghost (Payen and Dowle, 2012) and has been commercially applied since.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of multi-depth slanted airgun source for deghosting

et al. 2014

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To obtain high-resolution of the subsurface structure, we modeled multidepth slanted airgun sources to attenuate the source ghost. By fi ring the guns in sequence according to their relative depths, such a source can build constructive primaries and destructive ghosts. To evaluate the attenuation of ghosts, the normalized squared error of the spectrum of the actual vs the expected signature is computed. We used a typical 680 cu.in airgun string and found via simulations that a depth interval of 1 or 1.5 m between airguns is optimum when considering deghosting performance and operational feasibility. When more subarrays are combined, preliminary simulations are necessary to determine the optimum depth combination. The frequency notches introduced by the excess use of subarrays may negatively affect the deghosting performance. Two or three slanted subarrays can be combined to remove the ghost effect. The sequence combination may partly affect deghosting but this can be eliminated by matched filtering. Directivity comparison shows that a multi-depth slanted source can signifi cantly attenuate the notches and widen the energy transmission stability area.

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Section: Evaluation Metricsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Modeling of multi-depth slanted airgun source for deghosting

et al. 2014

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“…Finally, note that all the methods described here focus on acquisition approaches to mitigating the effect of receiver-side ghosts. However, similar approaches have also been proposed for extending the usable bandwidth emitted by the source (e.g., Ziolkowski, 1971;Egan et al, 2007;Cambois et al, 2009a;Parkes and Hegna, 2011).…”

Section: Introductionmentioning

confidence: 96%

Wavefield-separation methods for dual-sensor towed-streamer data

et al. 2013

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A dual-sensor towed streamer records the pressure and vertical component of particle motion associated with the incident wavefield that may be used to separate the wavefield into its upand downgoing parts. This procedure requires information about the water properties (wave-propagation velocity and density) and is robust in the presence of errors in the estimation of these quantities of the magnitude likely to be encountered. In practice, the particle motion data recorded by current towed marine streamers encounter very strong mechanical noise such that, for the lowest frequencies, the wavefield separation must be approximated by deconvolving the ghost function from the pressure data. This procedure requires information about the streamer depth and is robust to small depth errors over the frequency range for which it is required for dual-sensor streamer processing, but it is much more sensitive if applied over the bandwidth necessary to deghost pressure data acquired at a conventional streamer depth. The signal-to-noise ratio can be further enhanced by recombining the up-and downgoing pressure fields at the sea surface, which has the effect of applying a ghostlike filter to noise that is recorded by only one of the two sensors. In practical marine acquisition scenarios, spatial sampling is often insufficient to yield an accurate result, especially in the crossline direction. If each streamer is processed independently assuming that the wavefield propagation is purely inline, significant errors can be introduced. For arrivals with high emergent angles, errors may also be introduced even if the wavefield propagation actually is purely inline due to incorrect treatment of spatially aliased energy. However, these effects are almost entirely confined to very shallow events. They can be mitigated by using independently derived information about the crossline propagation angle and, for data comprising predominantly forward scattered energy, appropriate application of linear moveout.

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“…Recently, there have been several inventive ways of configuring streamers, or using dual sensors, to remove the receiver ghost, and there have also been some innovations on source geometries with the motivation of removing the source ghost (e.g., Hill et al, 2006;Cambois et al, 2009). With these kinds of improvements to the signal, it is natural that there has also been some focus on improving the signal emitted directly from the source as well.…”

Section: Introductionmentioning

confidence: 97%

Estimation of bubble time period for air-gun clusters using potential isosurfaces

Barker

Landrø

2013

GEOPHYSICS

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We evaluated a method of estimating the relative bubble time period of air-gun clusters with an arbitrary number of guns. This was done by assuming incompressible flow and representing the bubbles as isosurfaces of the potential field to account for coalescence. The kinetic energy at the equilibrium radius was then compared to the equivalent energy of the single gun to estimate the relative change. The results agreed well with two-gun cluster measurements, but the lack of data does not allow us to compare with clusters containing more guns than that. We found that more compact configurations, such as a triangle instead of three guns in a line, gave a more rapid increase in the bubble time period as the gun separation decreased. This indicated that compact configurations were attractive for enhancing the low-frequency output from an air-gun cluster.

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Multi‐Level airgun array: A simple and effective way to enhance the low frequency content of marine seismic data

Cited by 23 publications

References 6 publications

Modeling of multi-depth slanted airgun source for deghosting

Modeling of multi-depth slanted airgun source for deghosting

Wavefield-separation methods for dual-sensor towed-streamer data

Estimation of bubble time period for air-gun clusters using potential isosurfaces

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