HR: 0830h
AN: S41B-02    [Abstracts]
TI: 3-D Wave Equation Based Pre-Stack Depth Migration and Directional Illumination Analysis
AU: * Jin, S
EM: jin@screenimaging.com
AU: Xu, S
EM: xu@screenimaging.com
AB: 3-D pre-stack depth migration has proven to be a critical process in identifying the potential targets for oil and gas exploration. A heterogeneous medium with strong velocity contrast and complex subsurface structures presents a great challenge to seismic imaging. Wave equation based migrations are accurate but usually very expensive, prohibiting their uses in production applications. Recent advances in efficient 3-D wave field extrapolators and the continued increase in computing performance are making application of these techniques to full 3-D pre-stack wave equation depth imaging more affordable. In particular, screen propagators in midpoint-offset coordinates using local velocity perturbations provide fast and accurate wave field continuation. In the case of complex structures with large velocity contrast, such as salt-related structures where the velocity of salt body can be 2-3 times higher than the surrounding sediments, imaging shadow zones may be present in the sub-salt and around the salt boundaries. In such situation, illumination study is a useful estimate to investigate whether these imaging shadows are caused by the acquisition geometry under a specific geological model or caused by the inaccuracy of migration algorithm. However, traditional ray-based illumination methods are based on high-frequency asymptotic approximation, causing fundamental limitations in applications to complicated sub-salt regions. Wave equation illumination method is a more powerful and more accurate tool to analyze the illumination strength of a specific target event and amplitude variations. Such information can also be used for optimizing the acquisition geometry design. A number of benchmark synthetic and field data examples will be presented.
DE: 0910 Data processing
DE: 0935 Seismic methods (3025)
SC: Seismology [S]
MN: 2005 Joint Assembly