GRT Depth Migration

With tighter constraints on budgets and schedules, a depth migration must do more than merely creating an image. A modern algorithm must provide a geologically robust image along with 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 is offset gathers which tend to contain noise induced by the algorithm, particularly 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 prone to error and provides a poor approximation of true amplitudes.

GRT migration is a ray-based method performed in the angle domain and offers many advantages over Kirchhoff. Results are based on incidence angle without the need for prior knowledge of 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 detecting rays in the angle domain, GRT solves problems of multi-pathing in a natural way.

GRT offers high-quality images and AVA-compliant angle gathers with enhanced angle information. With precise amplitudes, GRT images are ideal for well-ties, ensuring that seismic attributes are more geologically coherent.