Pre-Stack Areal Shot Record Migration in 2D and 3D

Pre-stack depth migration aims at the proper positioning of reflection energy (including diffractions) especially important for complex media. The result is a high resolution structural image. The process is characterized by a huge amount of computations, involved in the downward extrapolation of the prestack data. Especially for 3D surveys, full pre-stack migration takes up too much computer time to be economically justified yet. Rietveld et al. (1992) introduced the method of controlled illumination. which generates areal shot records by combining the field shot records in such a way that the related areal source wave field has a pre-defined shape at the target level. Migration of these target oriented areal shot records is done by conventional shot record migration (Berkhout, 1985, chapter 7; Rietveld et aI., 1992). Similar to conventional shot record migration, migrated areal shot records should be stacked to form the final prestack migration result. The computational effort for the migration of one' areal shot record is equivalent to post-stack migration. We will show results of this new approach to pre-stack migration on a 2D field data set. The first results, on 3D data will be shown at the presentation.