A Fast And Low Cost Alternative to Subsalt Wave Equation Migration Perturbation Scans

Subsalt velocity analysis using prestack wave equation migration scans through perturbed velocity models is an accurate but expensive approach. To reduce turnaround time and computation cost, we investigated an alternative approach for subsalt velocity analysis. In this approach, we first use the current best velocity model to perform one prestack migration to produce a subsalt image. We demigrate the subsalt image to the base of salt to produce demigrated zero-offset seismic data. Using this demigrated data as input at the base of salt datum, we perform a scan of post stack wave equation migrations through perturbed subsalt velocity models. We demonstrate the necessity of demigrating only to the base of salt in order to avoid significant image degradation and show the feasibility of this methodology using the 2D Sigsbee data set.