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Results
Summary Subsurface structure characterized by strong lateral and vertical velocity variations are difficult to image by Kirchhoff depth migration. In contrast, finite difference based migration schemes can easily take into account complex velocity distributions and can cope with the resulting complex wave propagations. However, finite difference prestack depth migration (FDPSDM) is very expensive in 3D. Indeed, for classical marine streamer data, the natural common shot FDPSDN algorithm involves tens of thousands of wavefield propagation in 3D and is therefore unpracticable today. We present a new cost effective 3D FDPSDM technique for streamer data which is a combination of a cylindrical wave migration and a time shift migration technique.
Summary Imaging complex geological structures required the use of dedicated tools that can handle complex wave propagation (e.g. Multi-pathing). One such tool is wavefield migration. The challenge is then to handle stepp dips in presence of severe lateral velocity variation while avoiding numerical artifacts. There are different wavefield migration approaches(Phase shift based approach, finite difference approach, mixed approach…)that do not fulfill equally these requirements. In this paper, we compare the behavior of several 3-D wavefield zero-offset migration algorithms (phase shift plus interpolation, split step Fourier, encountered in complex media, namely steep dips and strong lateral velocity variation.