A 3-D prestack depth migration case history with a velocity model update in the Gulf of Suez
3-D prestack depth migration requires an accurate 3-D velocity model. Fortunately, the migration results themselves can be inspected and used to improve the initial velocity model. The data can then be remigrated. In this paper we describe the application of this approach to a 3-D dataset acquired in the Gulf of Suez at an area of a diapiric salt structure with steep sides. We use the Kirchhoff summation method with ray tracing for the 3-D prestack depth migration. The velocity model improvement is based on inspection of residual moveout as a function of offset on common depth point gathers sorted from pre-stack migrated data. Migration with the correct 3-D velocity field produces gathers with no residual moveout. If moveout is present the velocities need to be adjusted. We based the velocity adjustment on only a few well-identified reflectors to avoid the result being influenced by the strong peg-leg multiples seen in the area. The moveout was measured by semblance analysis and converted to an update of the velocity model. The prestack migration was repeated after the model was updated. Shallow reflectors, including the upper surface of the salt diapir, were resolved better after the first update.
- OSTI ID:
- 542956
- Report Number(s):
- CONF-951013--
- Country of Publication:
- United States
- Language:
- English
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