1887

Abstract

Summary

Variable-depth streamer acquisition has become a popular solution for marine seismic acquisition to obtain broad bandwidth data: the curved cable profile produces notch diversity that minimizes residual ghost and the deep towing segment provides high S/N at low frequencies. However, there have been discussions in the industry regarding the fidelity of AV O response from variable-depth streamer data due to the obvious changes in frequency and wavelet with offset. To answer this question, we need to focus on these key questions: can we remove the ghost successfully? Can we compensate the earth absorption effect to balance the spectrum from near to far offset?

Based on the de-ghosting algorithm that is termed Ghost Wavefield Elimination (GWE) which inversion in the tau-p domain ( , Poole 2013), we analyse the influence of GWE on the AV O response by using 2D synthetic datasets which were modelled by visco-elastic wave equation (Kjstansson, 1979) with two streamer towing configurations - conventional flat tow (8m) and depth-variable way (7~50m). GWE was applied on both datasets and the results show that it is very effective in attenuating the ghost energy. Furthermore, the AV O responses obtained in GWE results are almost identical. However, both AV O curves still decay rapidly in far offsets. To compensate this, pre-stack depth migration that incorporates the synthetic Q model (Q-PSDM) was applied. The resulting AV O curves then match well with the Aki Richards synthetic.

Our approach was then applied on a recent BroadSeis survey offshore Vietnam with source/receiver de-ghosting, shallow water de-multiple, advanced depth imaging and proper Q compensation. The high resolution common image gathers (CIGs) were then compared with the well synthetic gathers: AVO trends were picked along the top of sand layers and a good match was found within a frequency band of 5–60 Hz.

To summarise, we have demonstrated through both synthetic and real data examples that AV O fidelity is preserved for depth-variable streamer data with GWE pre-migration de-ghosting technology and ray path honouring pre-stack absorption compensation through Q-PSDM.

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/content/papers/10.3997/2214-4609.201412441
2015-05-11
2024-03-29
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References

  1. Wang, P., Ray, S., Peng, C., Li, Y. and Poole, G.
    [2013] Premigration deghosting for marine streamer data using a bootstrap approach in Tau-P domain. 83rd SEG Annual Meeting, Expanded Abstracts, 4221–4225.
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  3. Aki, K. and Richards, P.G.
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  4. Duval, G.
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