Abstract: Velocity Model Building in the Gulf of Mexico--An Old Story With a New Twist

Mike Witcombe

With the commercial availability of 3-D pre- and poststack depth migration, more and more attention is being focused by the industry on producing velocity models in a fast and reliable manner. Various methods have been presented in the past for producing 3-D velocity fields, but it should be realized that a method suited to one particular region is not necessarily the best solution in other areas. Much attention is currently being focused on developing high end, 3-D forward modeling packages for the more complex areas of the world. It should be remembered that in areas of more straight forward sedimentary velocities, new tools, in the form of desktop workstations and massively parallel super computers, can be used to good effect with some of the more traditional modeling approaches.

A case history will be presented that combines the use of a computer workstation with 2-D prestack depth migration and iterative 3-D poststack depth migration to produce a robust velocity model suitable for use with 3-D prestack or poststack depth migration on a Gulf of Mexico data set. The workstation allows us to quickly get a feel for the variation of subsurface velocity over the data set, with the aim of incorporating overpressure information into our model. 2-D prestack depth migrations were used to Q.C. and refine the model before running full 3-D poststack depth migration to delineate the salt sheets present in the area.

AAPG Search and Discovery Article #90981©1994 AAPG Pacific Section Meeting, Ventura, California, April 27-29, 1994