Dense, High-Resolution Velocity Model Building Onshore; Application to a Major Fault System in Western Desert - Egypt

The long turnaround of the velocity model building phase in the past has been the main drawback of the depth migration when compared to the time migration. To compensate for this, CGG has recently developed alternative methods to the time consuming layer stripping approach. The method described here is based on dense, volumetric picking of the residual move-out followed by non-linear finite-offset tomographic update. One single layer is updated.<br>Earlier published cases on similar methodology have been mostly in marine environment. The case test in this paper is onshore, in desert environment and contains a strong lateral velocity variation (up to 1500 m/s) across a major fault induced by a throw reaching 3 km. An important question is whether the new volumetric, tomographic approach is able to represent the complexity of the velocity model needed for pre-stack depth migration. Land data is also typically noisier, which may cause problems for the automated, dense volumetric picking approach described here.<br>The results from this study show that the new VMB approach may also be feasible onshore. In addition to giving an improved imaging in the vicinity of the problematic fault zone, it is also considerably less work-intensive. <br>