Optimum signal re-processing of multiple legacy surveys to improve pre-salt imaging in the complex Santos Basin, Brazil

Abstract

SantosBasin is emerging as one of the world's most promising exploration and production areas. The pre-salt region is complex, with fast carbonates, slow sediments, volcanic layers, and large fault systems. Together with the complicated overburden structures including carbonate layers in the post salt and stratified salt, high-resolution imaging is critical to better understand the producing fields and to facilitate development of others. High-resolution imaging relies on adequate illumination, seismic data with sufficient resolution and a good signal-to-noise (SNR), and an accurate velocity model. The accuracy of the velocity model is also dependent on the quality of seismic data. In the central Santos Basin, by combining several legacy surveys along different shooting directions, we show that the illumination of the target zones is increased. With signal processing technologies developed in recent years, we show that the SNR and resolution of the data were improved. Surface multiple attenuation is challenging in this area due to the existence of high-velocity, steepdipping post-salt carbonates and stratified evaporites. We show that multiple prediction is improved by the larger crossline aperture enabled by the incorporation of all the legacy data; therefore, improved multiple elimination was achieved. With the reprocessed higher resolution and higher SNR data and increased azimuth sampling, a more accurate velocity model is inverted by contemporary model building technologies. Finally, delivering high-resolution presalt imaging.