A Strategy For Attenuating VSP Migration Artifacts: Local Beam Migration

Yu, Jianhua (BP America Inc.) | Hornby, Brian (BP America Inc.)



VSP-derived images can suffer from severe migration artifacts where the migration "smiles" resulting from the wave-equation and ray-based migration approaches are not be canceled out completely. These artifacts primarily result from limited acquisition aperture and limited receiver array used in the data acquisition. This can be especially important with sediments below a complicated salt structure where the desired data contains not only signals of interest but strong undesired diffractions and other arrivals caused by the sharp velocity contrast. In this work, we demonstrate how to improve migration image quality by decomposing wavefields into local beams in the migration process and optimizing the decomposed local beams using a generalized imaging condition. Tests on synthetic and field data indicate that this migration scheme is capable of attenuating migration artifacts and yields the image with less noise. However, some care should be taken when dealing with high angle structure such as faults and salt flanks where more beams will be required.