3D Seismic Depth Imaging and Velocity Model Building in Anisotropic Media: Serri Oil and Gas Field, Saudi Arabia

Seismic imaging is a significant element in hydrocarbon exploration to locate drilling prospects and it relies mainly on an accurate velocity model. Prestack depth migration (PreSDM) versus traditional post-stack time migration has become a common method for seismic velocity model building and imaging. This methodology accounts for seismic velocity anisotropy of the propagating waves in the subsurface with a higher level of accuracy in positioning the seismic events in their true positions in the subsurface. In this thesis, we examine a 303 km2 of 3D seismic data acquired by Saudi Aramco in the Serri field of North-West Saudi Arabia. The dataset is diagnosed to be of extremely poor reflective quality likely due to seismic anisotropic effects caused by shale deposits. Our main goal was to produce an enhanced and better focused seismic image that is geologically accurate and interpretable This study develops a practical method for building an anisotropic velocity model to be further used in the anisotropic PreSDM. Based on this study, three main approaches have made a significant impact on the improvement of seismic imaging: (1) analysis of elastic reflection coefficients characterizing heterogeneities in the subsurface, (2) study of the variation of the reflection coefficients with the angle of incidence, and (3) a detailed characterization of the P-wave propagation velocity field. The seismic imaging results showed that PreSDM provided a significant improvement of the seismic image quality. Moreover, the anisotropic PreSDM provided more continuous and brighter reflections than the isotropic PreSDM