Multiple attenuation for shallow-water surveys: Notes on old challenges and new opportunities

Abstract

Challenges are reviewed for multiple-attenuation workflows for shallow-water surveys, including the 3D surface-related multiple elimination (3D SRME) workflow as well as workflows that combine wavefield extrapolation and 3D SRME. A proposed workflow improves on 3D SRME results for shallow-water surveys while aiming to remove all surface-related multiples rather than just a subset from those multiples. The key step in this workflow is a 3D SRME prediction of free-surface multiples using two input data sets — the recorded data and another data set preprocessed to remove a subset of water-layer-related multiples. This approach reduces some of the amplitude distortions in the SRME model and leads to overall improvement in results. Properties of the proposed workflow are illustrated with data from two shallow-water surveys acquired in the North Sea with multimeasurement steamers. Processing of the densely sampled 3D shot gathers obtained by joint interpolation and deghosting using the multimeasurement data provides more accurate wavefield extrapolation, better constrained adaptive subtraction, and overall better multiple-attenuation results than processing data from each streamer independently.