| Interferometric migration is a recently developed method that is proved to be a powerful imaging tool for vertical seismic profile (VSP) data. Synthetic and field data examples demonstrate that, it is robust to velocity estimation errors, and can sometimes produce reflectivity images much more accurate than standard migration methods. In this thesis, a wave-equation interferometric migration (WEIM) method is developed for three-dimensional (3-D) migration of VSP multiples. With WEIM, for each receiver gather of 3-D VSP data, only one 3-D receiver gather of travel times and one 3-D wavefield extrapolation need to be calculated for the migration of free-surface multiples. Compared to the expensive acquisition and processing costs of a 3-D surface seismic survey, the tremendous efficiency in obtaining a 3-D subsurface image volume by migration of 3-D VSP free-surface multiples suggests that a 3-D VSP survey might also serve as a cost effective four-dimensional monitoring tool for some oil fields. WEIM is also applied to image vertical subsurface structures. such as salt flanks which are difficult to image by conventional surface seismic surveys. |
