Predicting subsalt dip‐dependent illumination variations using density bubbles with RTM migration

Summary Variable illumination cause significant problems when imaging subsalt or other geologic regions with velocity variations. Much effort is taken to identify and improve the artifacts from these illumination variations, with limited success. A key challenge is that the illumination variations are a strong function of dip angle. Methods based on a single illumination value at each depth location or based on predefined reflector dip will be incomplete. We propose using “density bubbles” to identify the illumination variations as a function of dip, as seen in figure 1. These density bubbles are spheres of moderate density increase inserted in a model used to produce synthetic data. After the synthetic data is processed and migrated, a human can easily see illumination variations as a function of dip. This can be an essential QC mechanism to evaluate different acquisition approaches and imaging approaches. And after imaging, these density bubbles can be an effective interpretation tool for the interpreter to guide him on the imperfections of the seismic image produced with the real data that corresponds to the synthetic data.