Migration

I then migrated with the velocity in Figure 12. Figures 13 and 14 show the same two slices through the migration cube as Figures 4 and 5. Overall image quality is improved. Comparing Figures 4 and 13 we can see better focusing of the chalk reflector at `B'. We see more reflectors within the basin structure at `C'. The fault at `D' is sharper. In addition, the reflectors under the salt edge are more continuous and extend further.

In the second comparison, Figures 5 and 14, we see similar improvement. We see better focusing of the chalk reflector at `B'. The basin reflector (`C') is much better focused. The depth slice shows significantly more structure and better focusing (`E') with the new velocity. The biggest improvement is seen at `A' and `D'. At `A' we again see better continuity and focusing of reflectors under the salt edge. At `D' little reflector coherence is seen in the initial migration. The migration with the updated velocity shows much more reflector coherence.

 

cube.mig1.1
Figure 13 Slice through the migrated cube using the velocity of Figure 12.

 

cube.mig1.2
Figure 14 A second slice through the migrated cube using the velocity of Figure 12.

Figure 15 shows the semblance for the bottom twelve reflectors in the updated image. Generally it was possible to follow the reflectors further than in the initial migration. We also see generally less moveout in the CRP gather than the initial image.

 

smooth.3d.vel1
Figure 15 Picked semblance along the bottom 12 reflectors used in tomography.