Methode De Filtrage Du Fantome: Application a Des Cas Reels*

Fail, J. P.; Layotte, P. C.

doi:10.1111/j.1365-2478.1970.tb02123.x

Cited by 3 publications

(1 citation statement)

References 3 publications

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“…It was the subject of a patent (Prescott, 1935) and variations on the same theme have been described for seismic surveys on land many times. the result being achieved by the progressive detonation of a long charge or multiple charges, or by summing separate recordings made with shots at different depths in the same shot-hole (Shock, 1950;Van Melle and Weatherburn, 1953;Musgrave et al, 1958;Seabrooke, 1961;Hammond, 1962;Sengbush, 1962;Martner and Silverman, 1962;Fail and Layotte, 1970). …”

Section: Vertical Distribution Of Seismic Sourcesmentioning

confidence: 99%

Three‐dimensional air gun arrays

Smith¹

1984

SEG Technical Program Expanded Abstracts 1984

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02 03 04 05 06 07 08 09 10 11 12 I ! I / 1 \ , I, I, FIG. 4. Signature 33 degrees behind array. Scale factor = 0.495. (Figure 2). The scale factors shown in the figures give the relative amplitude scaling between these three figures. Modeled radiation patternsThere are many parameters that may have an effect on the observed radiation patterns. Some of these are the 2-D array geometry, air gun distribution within the array, variations in the firing times of the air guns, and variations in the depths of individual air guns. The radiation pattern due to the array geometry can be modeled using equally weighted ideal dipole sources (point source plus free-surface ghost) at each air gun position within the array, and summing these at desired observation points. Such modeling predicts an isotropic radiation pattern for the square array, symmetrical directionality with more energy in the in-line vertical plane for the wide array, and symmetrical directionality with more energy in the crossline vertical plane for the long array. Other observed radiation pattern properties for these three arrays must therefore be due to other factors.Modeling of the far-field radiation patterns using measured near-field air gun signatures allows the effect of the gun distribution within the arrays to be observed. Because the subarrays are designed with the largest guns in the front and the smallest guns in the rear. some forward directionality results from gun distribution. This elect does not completely account for the strong forward directionality observed for the wide array.The firing times of each individual air gun and its depth can also be incorporated into the model. Because the firing times were closely controlled and monitored during data collection, they will not have a significant effect on the radiation patterns. The depths of the air guns were also monitored during data collection and displayed a rather wide variation within the arrays. Variations of more than 2 m above or below the nominal air gun depth of 10 m were observed. even within a single subarray. These gun depth distributions were also observed to be slowly varying from shot to shot. Including these observations in the radiation pattern modeling scheme provides yet a better prediction for the observed radiation patterns.In conclusion, the observed data confirm our ability to make field measurements of 3-D radiation patterns, allowing us to observe the effectiveness of various array designs. For instance, wide arrays are designed to minimize out-of-line scattered energy and maximize in-line energy. The observed data show that the range of take-off angles for which the energy is less than 6 dB down from the peak energy is nearly twice as wide in the in-line plane for the wide array as it is for the square array. Similarly, long arrays are designed to minimize in-line multiple energy. The observed data show that the radiation pattern, as measured above, is almost onefourth as wide in the in-line plane and nearly twice as wide in the crossline plane ...

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Section: Vertical Distribution Of Seismic Sourcesmentioning

confidence: 99%

Three‐dimensional air gun arrays

Smith¹

1984

SEG Technical Program Expanded Abstracts 1984

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References

1976

Introduction to Digital Filtering in Geophysics

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Broadband seismic over/under sources and their designature-deghosting

et al. 2017

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The source depth influences the frequency band of seismic data. Due to the source ghost effect, it is advantageous to deploy sources deep to enhance the low-frequency content of seismic data. But, for a given source volume, the bubble period decreases with the source depth, thereby degrading the low-frequency content. At the same time, deep sources reduce the seismic bandwidth. Deploying sources at shallower depths has the opposite effects. A shallow source provides improved high-frequency content at the cost of degraded low-frequency content due to the ghosting effect, whereas the bubble period increases with a lesser source depth, thereby slightly improving the low-frequency content. A solution to the challenge of extending the bandwidth on the low- and high-frequency side is to deploy over/under sources, in which sources are towed at two depths. We have developed a mathematical ghost model for over/under point sources fired in sequential and simultaneous modes, and we have found an inverse model, which on common receiver gathers can jointly perform designature and deghosting of the over/under source measurements. We relate the model for simultaneous mode shooting to recent work on general multidepth level array sources, with previous known solutions. Two numerical examples related to over/under sequential shooting develop the main principles and the viability of the method.

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Methode De Filtrage Du Fantome: Application a Des Cas Reels*

Cited by 3 publications

References 3 publications

Three‐dimensional air gun arrays

Three‐dimensional air gun arrays

References

Broadband seismic over/under sources and their designature-deghosting

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