Prestack 3-D TAU migration and velocity analysis: Application to seismic data from offshore Abu Dhabi

We managed to apply a prestack 3-D τ (a depth variant) migration on a 3D seismic test data set from offshore Abu Dhabi using the final developed interval velocity model. The velocity model was built through an initial series of 2-D TAU migration velocity analysis, and supplemented by 3-D subset migration. A 3-D TAU migration velocity analysis was used to apply the final two updates to the model. The final interval velocity model provided low residuals in common-image gathers and agreed well with velocities from the four wells located in the region. This velocity model also included all the main expected features of the region like the low velocity anomaly and the major fault present in the reservoir area. Based on the estimated velocity model we expect that the major cause for the poor image quality in the reservoir area is a combination of a high velocity anomaly followed by a low one side by side up shallow and separated by a fault. This phenomenon is well reflected in the velocity model. Using the velocity model we apply a final 3-D prestack TAU migration, which resulted in an image of the region that mapped some of main expected characteristics of the subsurface including reflections from the major fault.