Normalization of Kirchhoff imaging for variable fold

Nizar Chemingui and Biondo Biondi

nizar@sep.stanford.edu, biondo@sep.stanford.edu

ABSTRACT

For multichannel recording, abundance of data traces represents a key element in the processing stage and the quality of the final image. Therefore, seismic acquisition geometries are often designed to optimize the fold coverage in the survey. However, this often neglects a crucial processing requirement: a good distribution of offset and azimuth in the CMP bins. The processing of seismic data for amplitude inversion requires both accuracy of algorithms and proper handling of irregular geometry. Sampling irregularities in the form of varying fold may introduce noise, cause amplitude distortions, and even structural distortions when wave equation processes such as DMO, AMO, and prestack migration are applied to the data. In the context of amplitude-preserving processing, we present a new development in our true-amplitude sequence for processing wide-azimuth 3D surveys. We extend the concept of multiplicity to wave equation processes and explore a normalization procedure to correct for the variations in fold distribution. Given a common-offset common-azimuth 3D subset, we correct for the fold variations by normalizing each input trace according to the local fold of its corresponding bin. The normalization corrects for data trace redundancy but does not account for missing traces or for the spatial distribution within local bins. Results of the application of integral migration and integral AMO as summation over the preconditioned data have proved to correct and equalize the imaging processes for the effects of fold variations.