Delta weights for footprint suppression in 3D prestack migration

Joanna Kathleen Cooper, Gary F. Margrave, Donald C. Lawton

When compared to prestack-migrated images of a fully-sampled ("exhaustive") numerical model seismic dataset, images from decimated (under-sampled) datasets display acquisition footprint artefacts. In this study, a weighting scheme for prestack Kirchhoff migration that attempts to compensate for irregular illumination of image points, which was previously shown to have promise in 2D, was implemented in 3D using MATLAB. The method was applied to the exhaustive and decimated datasets, with the purpose of examining its ability to suppress footprint artefacts. The scheme involves hit counting of delta angles for traces input to the migration, where delta describes the dip and azimuth of the vector bisecting the source-to-image-point and receiver-to-imagepoint rays. Though the method does not address footprint related to the aperture of the survey, it does appear to reduce the severity of footprint artefacts consisting of periodic amplitude variations in the interior of the survey, without losing the ability to resolve edges in the migrated images. The method produced results that are better than a comparable common-offset-weighted migration.