Footprint reduction by angle-weighted stacking after migration

Joanna K. Cooper and Gary F. Margrave

ABSTRACT

In prestack migrated seismic data, acquisition footprint artifacts appear to manifest as residual migration wavefronts. Due to inadequate spatial sampling, the wavefronts do not completely destructively interfere. Prestack migration algorithms have different ways of sorting, regularizing, and weighting the input data, which result in differing abilities to deal with poor sampling. Additional normalizations are performed on traces after migration but before stacking to form the final migrated image. In this paper, a weighting scheme in a Kirchhoff shot record migration that partially compensates for irregularities in the angle-dependent illumination of an image point is described and assessed. Though the weights are applied in the context of migrating common-source gathers, the weights are dependent on the locations of all shots and receivers in a survey, and are applied to traces during the stacking process after migration; they are therefore not limited to the case of shot record migrations. The weights are a function of image point location and delta, an angle describing the direction of the vector that bisects the source-to-image-point and receiver-to-image-point rays. The method, when applied to 2D model data shows potential for reducing footprint artifacts. The same type of weights can also be applied in the case of 3D data.

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