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oa A Perspective on 3-D PSDM in Compressive Tectonics
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 4th International Congress of the Brazilian Geophysical Society, Aug 1995, cp-313-00216
Abstract
3-D Prestack Depth Migration (3-D PSDM) is becoming the ultimate tool for seismic imaging in complex areas. Now generally available, this technique is becoming more efficient and cheaper to use, thanks to the ever growing power of today's massively parallel supercomputers, the availability of large memory storage and very fast VO capabilities. However, one should bear in mind that 3-D PSDM cannot be used as a black box; in fact, its success depends on three procedures : 1) deriving and updating an appropriate velocity model, 2) performing careful QC at every step during the imaging process, and 3) using a robust method for computing traveltime tables and other Green function attributes. In areas such as the Gulf of Mexico, where the velocities are well-known and varying smoothly, 3-D PSDM does not always need to follow these three steps and can be applied with success in almost a blind way with most algorithms. In more structured areas such as the North Sea, where large horizontal heterogeneities exist in the velocity field, one should be more cautious: the main difficulty there is to derive an appropriate layer-based velocity model. Finally, in very complex areas such as compressive zones, the challenge is still ahead. In those areas, if not used carefully, 3-D PSDM can yield very poor results and is not cost -effective. In this case, we propose to use first an alternative, cheaper 3-D imaging method to evaluate the difficulties involved. If 3-D PSDM is then justified, we recommend following very carefully the three steps mentioned above.