Velocity model building for tilted orthorhombic depth imaging

Abstract

Recently, tilted transverse isotropic (TTI) imaging has become a standard practice in deep water Gulf of Mexico (GOM) to resolve the anisotropic effects of wave propagation in salt-withdrawal mini-basins. Tilted orthorhombic (T-ORT) anisotropy, which usually represents parallel-aligned fractures normally embedded in tilted thin sedimentary layers, is a less-restricted assumption and can be applied to more complicated geological formations. This paper focuses on the key components of T-ORT depth imaging: T-ORT ray tracing, the procedure to build initial T-ORT models, and T-ORT tomography. With a real multi-azimuth (MAZ) dataset in the Perdido fold belt, GOM, we demonstrate the effectiveness of the T-ORT velocity model building, where the estimated T-ORT anisotropic parameters are consistent with the geological setting. T-ORT prestack depth migration flattens common image gathers (CIGs) in all azimuths and results in improvements in image focusing, as well as spatial positioning of complex structures in the area of interest.