Use of Elastic Forward Modeling to Remove Complex Coherent Noises

Summary In the deep-water Campeche Bay area of the southern Gulf of Mexico, there are many complex shallow salt bodies and carbonate rafts that generate a significant amount of coherent noise energies, collectively for all non-primary reflection energies, as a result of the high impedance contrast between these bodies and the surrounding sediments. These noise energies include surface-related salt-diffracted multiples, interbed/internal multiples, bounces between salt bodies, and other types of prismatic waves as well as converted shear waves. These coherent noises cause difficulties in interpreting base of salt and subsalt seismic events. Identifying and removing them is crucial for optimal seismic imaging of subsalt targets. We propose a method to model these noises using a geological imaging model and elastic finite-difference forward modeling. The method requires that the shallow part of the geological imaging model be accurate. We first compute elastic synthetic data using the model. Then, we migrate the synthetic data to generate a noise model in the image domain and use this noise model to pattern-match with another image volume migrated using field data. In this way, we can identify noises in the field data and remove them adaptively to obtain a cleaner image of the recorded reflectivity.