2D Depth Velocity Analysis without Tomography

Summary A module for measuring the depth velocity field (interval velocity, epsilon, delta) from 2D seismic data is presented. Upward ray tracing from selected reflector segments is used to select traces from the whole prestack volume whose angle of incidence equals angle of reflection on the segment. These traces can then be combined to form common offset gathers. Velocity can be scanned in any zone and the velocity, with the common offsets that are flattest and most coherent, picked. This methodology is fast, robust, and effective; and since it works on the prestack data, it removes the need for iterative depth migrations. It also allows the user to inspect the data as the model is formed. Since only a small set of strong reflector segments are selected it is robust in the presence of noise and broken up signal. It may be run routinely on 2D seismic lines.