Imaging Enhancement of VSP Data with Optimal Aperture RTM

Seismic images from vertical seismic profile (VSP) data usually have higher signal-to-noise ratio and higher resolution than images produced from surface seismic data since receivers are closer to the targets. However, VSP images often contain strong migration artifacts (known as migration swings), due to the asymmetric acquisition geometry and the limited acquisition aperture. It is well known that the migration swings can be attenuated by limiting the migration aperture. In this paper, we propose a data-driven method to automatically select optimal aperture for VSP reverse time migration (RTM). Our method is based on the local coherency analysis of the migrated common image gathers (CIGs) in the source offset domain. By attenuating the long "tails" of the migrated events in the CIGs, we show that migration images can be enhanced. Numerical examples for synthetic data demonstrate the effectiveness of our proposed method for suppressing migration artifacts in VSP RTM images.