Bullwinkle: A unique 3-D experiment

Abstract

In the spring of 1988, Shell Offshore Inc. acquired two orthogonal three‐dimensional (3-D) surveys at Prospect Bullwinkle, located in the Green Canyon area of the Gulf of Mexico, to aid the development program which began later that year. Two surveys were acquired because of the complexity of the salt structures in the vicinity of the prospect. The independent acquisition and processing of two surveys shot perpendicular to each other provided a unique data set for checking the quality and accuracy of standard 3-D techniques. The high development cost of this deep water (410 m) turbidite field supported the acquisition of two 3-D data sets to provide a valuable redundancy for stratigraphic interpretation. This large scale 3-D experiment has been analyzed in terms of interpretive impact. Detailed comparisons of the seismic images away from the salt complex show good agreement between the two surveys and verify the relative accuracy and repeatability of the acquisition, processing, and interpretation techniques. Structural comparisons between the surveys show that acquisition oriented in a strike direction to the primary salt face yields a superior sediment image, particularly near overhung salt. An examination of the effects of shooting direction on small scale stratigraphic resolution illustrates the importance of fine sampling in the dip direction to the features of interest. Amplitude maps extracted for the main bright spot level show differences in areal continuity that are large enough to affect the geologic model of the prospect.