Summary

Wave-equation datuming cannot replace statics in all applications, and it is not a panacea to be applied under all circumstances, but under certain conditions, when topographic relief is substantial and when the assumption of large static shifts is invalid, it is the most accurate and appropriate method of redatuming. This can be very helpful in the early stages of data processing when not much is known about the geological structure and the subsurface velocity distribution.

Redatuming is applied early in the processing flow and it will affect all subsequent processing. Proper redatuming to a flat surface is crucial for algorithms which assume hyperbolic form, such as velocity analysis. It is also advantageous because the most efficient DMO and migration algorithms assume a flat, regularly-sampled processing datum. Since the datuming velocity is known, it can be incorporated into the prestack migration velocity field so that when the data are migrated from the flat datum, the effect of the datuming is counteracted.

In the example I presented in this chapter, I showed that upward continuing the data to a flat regularly sampled processing datum with Kirchhoff datuming is superior to elevation statics. It offers a relatively painless way of obtaining a preliminary structural image that does not require a detailed knowledge of the subsurface velocity distribution. This is because stacking and migration velocities are more accurately and easily determined without the unnecessary complication of nonhyperbolic distortion, which would arise if the data were processed from the topography or after elevation statics.