Schlumberger

Enhanced Migration Amplitude Normalization

Improved acquisition artifact reduction using Voronoi weighting

Irregularities in acquisition geometry can result in the identification of acquisition footprints as anomalous amplitude and/or phase artifacts in seismic volumes. Conventional migration normalization approaches are based on CMP fold; however, this does not take into account the spatial distribution of traces within, and in the vicinity of, the CMP bins.

We offer an alternative normalization scheme based on Voronoi polygons that can be used as an effective alternative to other methods such as various prestack regularization techniques; particularly in areas where the acquisition footprint is relatively mild.

Normalization scale factors are computed based on the spatial distribution of traces. For each CMP within an offset plane, a polygon is constructed around that location such that the polygon contains all points that are closer to that location than any of the surrounding points (see the image on the right). The size of each Voronoi polygon is an indicator of the "area of influence" of each seismic trace, and a set of normalization weights is then derived based on the area of the Voronoi polygons.

Improved amplitude normalization compared to fold-based approaches

The result is that input traces are scaled down (relatively) in high-fold areas where many traces within CMP locations can lie close together, and this reduces anomalous artifacts in the migrated data. As this weighting scheme is based on the areal distribution of traces, application of this normalization approach can also significantly reduce the level of artifact created by areas of missing coverage compared to conventional fold-based methods.

Voronoi normalization can be applied to prestack migrations, in either the time or depth domain, based on offset or azimuth planes.

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WesternGeco

Improved Amplitude Stability Across Full Offset

Voronoi weighting improves amplitude normalization in prestack migrations.
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