Equivalent offset migration: the implementation and application update

Xinxiang Li, Yong Xu, John C. Bancroft

We have some improvements about equivalent offset migration (EOM) method. In 1996, we presented a new algorithm to implement the construction of CSP gathers, which is more accurate and also faster than the old algorithm used in the 1995 version ProMAX code (CSP Gathers). As a result of our investigation about the amplitude distribution and scaling during EOM process, we found out several ways to improve the quality of the CSP gathers, as well as the final image sections. Most of them have been implemented in the new code in ProMAX as different options, such as

- Amplitude scaling;

- Migration aperture itation;

- Asymptotic solution;

- Trace fold division;

- Double sided CSP gather;

- Output the CSP trace fold gather.

In addition, a simple 45 degree phase shift (RJW filter) module is developed independently for the migration phase correction. It can be used before or after CSP gather construction, or even apply this filter on the final image section.

Practical applications of this new version of "CSP Gather" give better results. The most evident improvements are:

- the quality of CSP gather,

- the migration velocity analysis on CSP gathers,

- the final image section, and

- providing better model data for CSP statics analysis.

The ProMAX module is now ready for 2D data processing. The 3D version is a later work.