Advantages and Disadvantages of Surface and Downhole Seismic Illustrated by Processing Results of 3D VSP and 3D+VSP

Comparative analysis of Surface Seismic (SS) and VSP shows that each application has its own advantages and disadvantages. Surface Seismic never provides true velocity model and true signature. This is the reason for low resolution and inefficient processing of converted PS waves. In fact modern SS is on the limit of efficiency being still inadequate in many applications. VSP provide true velocities and true signature but quickly loses its efficiency in the vicinity of well. This is shown as comparison between Walkaway and CDP section. Example of 3D+VSP processing results shown that in this combined application signature and velocity model from VSP may be used to improve efficiency of Surface Seismic.