Understanding subsalt illumination through ray-trace modeling, Part 1: Simple 2-D salt models

The complex structure and high velocity contrast of salt in the Gulf of Mexico create a difficult seismic imaging problem. 3-D prestack depth migration (PreSDM) of seismic data has allowed imaging of reflectors under the salt sheets and of detached bodies of irregular shape. But 3-D PreSDM cannot fill in shadow zones below salt where little energy is reflected. Additionally, amplitude variations caused by salt structures focusing or dispersing seismic energy are usually poorly handled by 3-D PreSDM. Ray-trace modeling can clarify subsalt imaging problems, and the modeling results should be incorporated into exploration and development plans.