Background

Figure 1 is a 2-D line taken from the 3-D survey in the North Sea. It shows the stacked result after we have applied a 2.5-D pre-stack Kirchhoff depth migration. The salt body can be seen in the middle of the section. The reflector we wish to image obviously fades then disappears as it nears the salt body. Figure 2 shows two common reflector point (CRP) gathers taken from this section. The reflector is visible in the CRP gather that is farther from the salt but is almost totally missing in the second CRP gather. There is some coherent energy in the mid-offsets. By analyzing a synthetic dataset based on this real data we will show that this behavior is due, at least in part, to illumination problems.

 

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Figure 1 PSDM section from the real dataset

 

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Figure 2 Left: CRP gather from field data at surface location 8500 m showing the flattened reflector. Right: CRP gather from field data at surface location 7500 m showing coherent energy at mid-offsets.

 

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Figure 3 Synthetic velocity model