Improved subsalt images with shot patch-based angle gather illumination weighting

One way to address the problem of weak subsalt illumination is through angle gather illumination weighting (AGILW). In this technique, synthetic data mimicking the field data are generated and migrated the same way as the field data. Illumination weighting scalars are obtained by measuring coherent amplitude on the synthetic migration gather. This weighting scalar can be applied to field data to enhance signal and attenuate noise. In this paper, we propose a refinement of this approach: shot patch-based angle gather illumination weighting, based on RTM 3D angle gathers. Instead of using the traditional approach of migrating all shots in a survey to form one set of angle gathers, we partition the input shots from both field and synthetic data into smaller shot patches and keep the migration gathers separate for each shot patch. This new approach can limit crosstalk between signal and noise from different shot patches, and can more effectively attenuate noise and improve subsalt images. We demonstrate the effectiveness of our method with both 2D synthetic data and 3D field data.