GRT Depth Migration

With tighter constraints on budgets and schedules, a depth migration must do more than just create an image. A modern algorithm must provide a geologically robust image and AVO-ready, true amplitude pre-stack gathers.

Ray-based migrations, such as Kirchhoff, have severe problems in storing and accessing multiple ray events resulting in difficulty in imaging areas of geological complexity. The output from these migrations are offset gathers which tend to contain algorithm induced noise on far offsets. To use these gathers in AVA/AVO studies, we must first pre-condition and then transform them to incident angle gathers. This process is error prone and provides a poor approximation of true amplitudes.

GRT migration is a ray-based migration scheme performed in the angle domain and provides many advantages over Kirchhoff. Results are based on incidence angle and no knowledge is required on true local dip or mapping between offset and angle. Migration amplitudes are proportional to the local angle- and azimuth-dependent reflection coefficient. Regularised input data is not required. By identifying rays in the angle domain, GRT solves problems of multi-pathing in a natural way.

GRT provides superior images and AVA-complaint angle gathers with fuller angle information. Accurate amplitudes mean GRT images are better for well-ties and seismic attributes are more geologically consistent.