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Summary We successfully applied anisotropic Kirchhoff prestack depth migration (AKPreDM) to a 3D data set from the Ewing Bank Oil Field, Gulf of Mexico to accurately map the target sands in depth. Initially, we used isotropic Kirchhoff prestack depth migration (IKPreDM) to perform the mapping of the reservoir sands. However, the depths estimated using the seismic data and those detected at the wells for the target sands showed excessive mis-ties (approximately 1100 feet). The results obtained after the application of AKPreDM showed that the misties were greatly reduced within a few tens of feet, therefore providing a better tie with the well tops. In this paper, we present the methodology employed in this case study, which includes the anisotropic parameter estimation. We also discuss the well tie results obtained after the application of AKPreDM and IKPreDM. We conclude that the effect of anisotropy (vertical transverse isotropy, VTI) should be taken into account to obtain seismic depth estimates that better tie the well depths accurately. |
