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3D
Multiple Elimination in the Gulf of Suez: Acquisition Design for Optimum
Processing Results
By
Ian M. Threadgold1, Norman C. Allegar1, Roald Gunnar van Borselen2, D.J. (Eric) Verschuur3, Ken H. Matson4
(1) BP Egypt, Maadi, Cairo, Egypt (2) PGS Geophysical, Walton-on-Thames, United Kingdom (3) Delft University of Technology, 2600 GA Delft, Netherlands (4) BP, Houston, TX
The Gulf of Suez (GoS) is a very mature basin, and is acknowledged for the
poor quality of the seismic data. Free surface and interbed multiples are the
most severe problems from a host of geophysical effects that mask primary events
on GoS seismic data.
BP Egypt established an in-country applied-research project (the GoS
Demultiple Project) to identify, evaluate, develop and apply techniques to
significantly improve seismic data quality on a very timely basis, and to assure
the continued development of a high quality prospect portfolio.
A 2D test program in 2001, provided zero-offset data which gave substantial
imaging improvements by allowing optimized application of 2D Surface-Related
Multiple Elimination (SRME) software, in the relatively shallow water (~60m) GoS,
in addition to further advancements such as low frequency adaptive subtraction.
Further work on source comparisons, and acquisition aspects, led to a novel
3D survey design for attenuating GoS multiples, with the prime tenet of
acquiring data that would meet the 3D sampling requirements of SRME algorithms.
The survey design includes:
· An optimized source to emphasize the low-frequency primary bandwidth
· A multi-azimuth component to aid in illumination and multiple removal
·
Near offset recording to provide pre-critical data for SRME, and
·
Adequately sampling the multiples in 3D for application of full 3D
and sparse inversion 3D SRME, and interbed multiple elimination software
Modeling indicates that the number of streamers, the streamer separation and
the sail line spacing play an essential role in improving the applicability of
3D
SRME algorithms.