Figure shows the migration results in the angle domain for the input data (Figure a), the estimated signal with the pattern-based approach (Figure b) and the estimated signal with adaptive subtraction (Figure c). By looking at the constant angle section (X=11000 m), it appears that more multiples have been removed with the pattern-based approach, especially below the salt where the multiples are the strongest. The common angle gathers corroborate this: a lot more energy from the multiples is present with the adaptive subtraction. Note that some multiple energy remains in both Figure b and Figure c where the salt body is present. These multiples have strong curvature and low-frequency content. These events are probably internal multiples bouncing between the sea bottom and the top of salt. Another pass of multiple attenuation in the image space Sava and Guitton (2005) could eliminate these reflections.

Figure 23

Finally, Figure shows a comparison of ADCIGs for the input data with multiples (Figure a), the estimated primaries with the pattern-based approach (Figure b) and the estimated primaries with adaptive subtraction (Figure c) outside the salt boundaries (X=4000 m). It illustrates once again that the pattern-based approach outperform the adaptive subtraction method with a cleaner panel.

Figure 24

The Gulf of Mexico example demonstrates that the pattern-based approach is an effective tool for multiple attenuation in complex geology. Although the multiple model obtained with SRMP presented some obvious flaws (short offset amplitudes), the proposed approach is able to attenuate the multiples while preserving the primaries. In addition, comparisons in the image space after migration on ADCIGs show that the pattern-based approach gives cleaner panels than adaptive subtraction.

5/5/2005