Robert S. Hobbs¹, Jerry Young¹, Bruce Ver West¹

(1) Veritas, Houston, TX

ABSTRACT: Multi-Directional 3D Acquisition and Processing; Salt Imaging in the Deepwater Gulf of Mexico

3D Pre-stack depth migration (PSDM) is commonly used for improving image quality adjacent and under complex salt bodies in the Gulf of Mexico. A study has been conducted within a minibasin of the Garden Banks area of the Gulf of Mexico to examine the benefits of combining multi-directional datasets together through depth processing to yield the most optimum sub-salt image.

Two 3D volumes of differing vintages but similar acquisition parameters were acquired with inline directions of 90 degrees to each other. These surveys were both processed thorough 3D PSDM independently with an identical velocity model and then merged into a combined final production volume. Seismic raytrace modeling accompanied the program to understand the effect of acquisition direction on subsurface image quality.

Varying structural dips within salt-surrounded mini-basins and the irregularity of the salt itself creates a complex scenario where one acquisition direction alone did not satisfy all imaging requirements in the basin. The differences in image quality could be understood through offset raytrace modeling utilizing the velocity model created in the depth migration stream. In general, the acquisition direction that was parallel to the predominate salt front in a particular area yielded the best sub-salt overhang image over the direction that was perpendicular to the salt front. The volume resulting from the combination of both processed datasets yielded the most optimum image given the structural complexity seen in the basin.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado