NORSAR is continuously exploring and developing seismic modelling techniques and their applications.
The research and development includes:
- Kirchhoff modelling. This modelling method is based on the Kirchhoff integral solution for calculation of the seismic wavefield between a source and a receiver. The method is robust, as in contrast to in conventional ray-tracing, the reflector can be very rough.
- Kirchhoff depth migration. Used in combination with the Kirchhoff modelling, this provides a very interesting tool to investigate the effect of ‘erroneous’ depth-velocity field in migration, in that the depth-velocity model for the two processes can be chosen independently.
- Green’s functions calculations. Green’s functions are one-way rays, usually computed separately for the shot and receiver sides of a reflector. When the rays are computed between the entire area of interest on the surface as well as at the target level, they provide a comprehensive data base of ray propagation information. Combined with efficient interpolation techniques, this is a valuable ‘raw-material’ for very efficient modelling of various survey geometries in conventional ray-trace modelling as well as with Kirchhoff and SimPLI modelling techniques.
- AVO/AVA modelling based on NORSAR’s well-stablished SMA technology (Simulated Migration Amplitude). The purpose is to investigate how much information can be expected to be obtained from an AVO/AVA-study, depending on the subsurface and the seismic survey.
The pictures show the Gullfaks reservoir area, a survey, and cross sections through pre-stack and migrated seismic, computed with the Kirchhoff modelling and migration.