ABSTRACT: A Radial 3-D Seismic Survey at Exxon's Grand Isle 16 Field, Gulf of Mexico

R. R. Beebe, W. K. Harrison

Grand Isle 16 field is one of several large salt diapirs that occur along the Bay Marchand salt ridge located along the southern boundary of the Terrebonne trough. Discovered in 1948, Exxon's oldest field in the Gulf of Mexico has produced 268 MBO and 417 GCFG from upper Miocene sands. Over 400 wells have been drilled for hydrocarbons found in three major plays: (1) updip truncation of steeply dipping reservoirs by salt, (2)

subunconformity accumulations, and (3) off-structure stratigraphic traps. Despite extensive drilling, significant potential remains to be evaluated.

We decided that a 3-D (three-dimensional) seismic survey is the best way to delineate the field's remaining potential. A rectangular survey with line shot using streamers was eliminated because of surface obstacles, high cost, and inefficient imaging where lines intersect the salt face and steeply dipping beds at an oblique angle. As an alternative, a radial survey was designed whereby lines radiate from a central point over the dome with infill lines added when predetermined separation between lines is reached. Following extensive 2-D (two-dimensional) testing, shooting with bay cables commenced in February 1988, and was completed in October 1988.

The processed data set consists of radial lines, circumferential lines, and time slices migrated using a two-pass technique. A regridded cube including inlines migrated with a one-pass (true 3-D) method is also included. This data became available for interpretation in July 1989, and has accomplished the goals of reducing acquisition cost and defining steeply dipping beds near the salt face.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990