Wave Equation Pre-Stack Depth Migration (PSDM)

3-D pre-stack depth migration (PSDM) constitutes the ultimate seismic imaging technology whereby each of the elemental pre-stack ray paths is individually imaged. The precursor to this imaging process is the calculation of travel-time trajectory maps through a given velocity depth model. Travel times must be computed for distances along the ray path segments from shot and receiver locations to the target element. A Kirchhoff algorithm can then be used to effect the pre-stack imaging. Wave equation migration is an accurate and robust alternative to Kirchhoff migration when multi-pathing and other complex wave modes occur.

Full two-way solutions of the wave equation such as Reverse Time Migration (RTM) have become commercially available for highly complex environments.

Pre-Stack Depth Migration is an important tool in modelling salt diapirs because of their complexity. The combination of tectonically complex overburden with variable lithologies in the Southern North Sea is one area that lends itself to the application of 3-D PSDM. Sub-salt imaging in the Gulf of Mexico is another.