Building Interval Velocity Model By Multiple Kirchhoff Pre-stack Depth Migrations

Obtaining an accurate interval velocity model is fundamental to successfully imaging complex geologies by using pre-stack depth migrations. However, the more complex the geology, the more difficult it is to find an accurate velocity model. A practical and fast approach is developed to update the interval velocity model for improved imaging. It is achieved by analyzing the multiple migration sections in the control lines by scanning the interval velocity from low to high percentages of the best available velocity models. The different percentages of the velocity model produce the reasonable or unreasonable, better or worse, imaging sections, partly, with varying degrees of clarity. The correct interval velocity can be estimated by integrating the right percentages of the velocity model, which produces the greatest improvement. Applying this approach to the real data shows that the estimated migration velocity reliably converges to the correct velocity. The CPU time consuming of the multiple migrations is not expensive, because multiple ray tracing or wave front construction for the different percentages of the velocity model are unnecessary.