The structural interpretation of prestack, depth-migrated seismic data has traditionally relied on full-offset stacks, attempting to take advantage of the stacking process to generate a high signal- to-noise ratio. However, in complex velocity environments (for example, subsalt), our observations suggest full-offset stacking can result in a lower signal-to-noise ratio than a partial stack of subsurface angle data. Despite the application of multipathing algorithms such as wave equation PSDM (prestack depth migration) or CRAM (common-reflection-angle migration), the full stack seismic data generally exhibit low signal-to-noise ratios, allowing for multiple valid structural interpretations. (Figure 1). This leads to a variety of common problems when assessing the prospect, well placement, trap/seal, volumes, and the differences in risking a four-way prospect from a three-way prospect.

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