Reverse-Time Migration of Converted S-Waves of Varying Densities

Abstract

Ocean-Bottom Node (OBN) acquisitions provide both non-converted and converted reflection energy. There is a clear advantage to independently imaging both P- and S-waves, as they provide more information collectively than either does alone. In many conventional converted-wave pre-stack migration algorithms, density is treated as a constant, which is not the real-life case on earth. S-wave velocity and density information is crucial for hydrocarbon detection because it helps in the identification of pore-filling fluids. In this paper, we focused on the effect of density on imaging, and developed a method of reverse-time migration (RTM) on converted s-waves of varying densities (VD-RTMCS). Phase correction was required prior to pre-stack migration to avoid constructive interference between data from adjacent sources. Synthetic data examples showed that when density variations were included, image profiles showed advantages in signal-to-noise ratio, vertical resolution and imaging of complex structures.