Plane wave source composition: An accurate phase encoding scheme for prestack migration

Abstract

Wave equation based shot profile migration can produce higher quality images than Kirchhoff type methods. However, the high costs largely limit their production use. The cost of a complete wave equation shot profile migration equals the cost of migrating a single shot times the number of shots migrated. Thus, methods to reduce the number of migrations required for a complete experiment while preserving the image quality are as significant as those that increase the efficiency for each migration. One way to increase the efficiency of shot migration is to extrapolate the linearly combined wavefields from multiple shots together. However, special treatment is needed to take care of the cross-term artifacts, which are generated in applying the imaging condition. This technique is generally called phase encoding. Plane-wave source migration is one such method to reduce the number of migrations. In this paper, we demonstrate the concept of plane-wave source composition from the phase encoding point of view. We will show that plane wave source composition is a specific phase encoding technique in shot profile migration. This study demonstrates a systematic error analysis for the plane wave source approximation in migration. This offers the possibility of applying different composing schemes in each migration. We can show that this approach can generate results nearly equivalent to those of shot profile migration. Numerical tests on the Marmousi model and others prove the efficiency and accuracy of this method.