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Is depth-variable streamer data AVO friendly? A study using both synthetic and real data
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, EAGE Workshop on Broadband Marine Seismic Data, May 2015, Volume 2015, p.1 - 5
Abstract
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 ( Wang et al. 2013 , 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.