3D Kirchhoff Pre-Stack Depth Migration
The key to Pre-Stack Depth Migration (PSDM) results is accurate velocity modeling and updating. iDEPTHing interval velocity modeling including geostatistical methodologies for velocity interpolation, and calibration provides well ties. PSDM generates CIG gathers for tomography.
PSDM shows improved imaging of salt boundaries, and dipping events are migrated to better positions of flat bed termination. More importantly, migration results are tied to all well markers around the salt.
All flat events indicated by green, blue, red, yellow and pink markers are well calibrated. A successful well was drilled based on PSDM results. Available PSDM results will guide more successful wells for drilling. Figures (PSDM-1 and PSDM-2) shows improved salt overhang boundaries and faults.
Reverse Time Migration
Reverse time migration is the most-accurate depth imaging solution, handling both steep dips and lateral velocity variations. It allows waves to propagate in all directions and in complicated geological environments. Reverse time migration is essential for sub-salt, overthrust, borehole and imaging from undulating terrain.
Pre-stack Residual Interactive Migration (iPRIM)
Pre-stack residual migration was applied on pre-stack depth migrated data from the North Sea. The result shows (below) the best seismic imaging under Zechstein salt and reflections from Platen dolomite inside the salt.
Enhanced imaging was the result of using a dip influenced residual move-out equation (ref. 2). No competitor could manage to bring out a reflection event from Platen dolomite, indicated as “1” in PRIM-1.
PRIM-1 (left) is the residual migration result of pre-stack depth migrated data from the North Sea. PRIM-2 (right) is the original stack of pre-stack depth migration.
Anisotropy Parameter Estimation
We have developed a scheme to tie well markers and flattening CIG gathers at the same time.
First, seismic velocities are calibrated with well data on regional basis and migrate with isotropic calibrated velocities.
Reflection tomography iterations, including internal and external loop, can update velocities, which define improved heterogeneity.
Anisotropic parameters are scanned around well locations, assuming locally layer-cake medium. Then we can have well-calibrated velocity cube and anisotropic parameter cubes for anisotropic migration.
Residual focusing and de-stretching will improve final stack. The whole procedures are designed to tie wells and improve images.