Online Journal for E&P Geoscientists

Owusu, John ¹; Lesnikov, Vladislav ^*1
(1) Saudi Aramco, Dhahran, Saudi Arabia.

Vertical Seismic Profiling (VSP) provides one of the best tools for identifying multiples and their generators. A special multiple analysis technique allows us to use VSP data to differentiate between surface-related and interbed multiples, and to determine which seismic reflectors are involved in the generation of a particular multiple. The technique is based on the joint analysis of VSP wavefields processed using three different types of deterministic deconvolution: waveshaping, reference trace and conventional trace-by-trace deconvolution. These different wavefields provide an opportunity to understand the mechanism of the multiple generation. The separated wavefields containing primary reflections only, surface related multiples, and interbed multiples can be generated from the deconvolved wavefields. This technique provides insight into the origin of residual multiples in surface seismic data, and helps in understanding the contribution of surface and interbed multiples to the total multiple wavefield contaminating the primaries at target intervals. Using this knowledge, multiple removal procedures can be designed and applied accordingly. For interbed multiples, the VSP data help to guide the removal process by providing the major reflectors involved in the generation of particular multiple events. VSP data also act as a QC tool for the surface seismic multiple removal procedures. The application of the proposed technique on real data from the Arabian Gulf demonstrated the usefulness of the information extracted from the VSP. The results confirmed the presence of strong multiple reflections in the surface seismic data contaminating the primaries of the Khuff formation. In addition to the interbed multiples, the VSP data analysis indicated a high contamination of multiples generated from the shallow reflectors. Reprocessing carried out on 3D seismic data using the information derived from the VSP multiple analysis showed significant improvements at the reservoir level.