Migration optimization through local phase alignment of partial migration images

Abstract

In the presence of complex scattering effects, such as those that may be encountered at rugose salt boundaries, the assumption of single scattering used by most true-amplitude production imaging algorithms may no longer apply. This may render true-amplitude imaging ineffective with regard to amplitude fidelity in complex areas. Often in these areas, complex scattering and wave behavior manifests itself as complex misalignment and wavelet distortion on partial image gathers, even when the velocity model is correct. Such misalignment affects the stack, and ultimately amplitude fidelity. Here we present a general optimization method for the alignment of partial images to mitigate the effects of complex scattering and complex wave behavior through salt. Although we do not claim that the method produces true amplitude fidelity, we have found that it can enhance migration images in complex shadow zones, and is an effective quality control tool to locate areas of complex partial-image misalignment that compromises amplitude fidelity.