Abstract
In thrust belt areas along the margins of the continental Rocky Mountains and other environments with structural complexity, changes in subsurface lateral interval velocity requires depth migration of conventional surface seismic surveys to correctly position events. The presence of accompanying thick shale units overlying prospective drilling locations demand the depth migration procedure also compensate for anisotropic effects of wave propagation in a titled coordinate reference system. We start by briefly identifying the types of environments that are prospective candidates for depth migration. Then we observe the incremental improvements in subsurface imaging by following a continuum of conventional methods leading to anisotropic depth migration results. Seismic depths to well depths are compared. Finally, methods to derive the required anisotropic parameters are discussed.
As the technical understanding of anisotropic wave field propagation deepens and more examples are found in case histories the role of anisotropic depth migration will become more prominent. Increases in compute capabilities portend that this will become the new standard for structural seismic imaging.
This procedure significantly improves the imaging of faults, formations and reservoirs by correctly describing their lateral and vertical geometry. Thus it is a major risk mitigator. Moreover, it offers a means to invert seismic data into the depth domain to be used by the entire geoscience community.
