Fast 3D velocity updates using the pre-stack exploding reflector model

Conclusions

We show that pre-stack exploding-reflector model synthesizes wavefields that provides migrated images with correct kinematics while decreasing the data size. Data reduction is achieved by combining the modeling experiments and is controlled by the number of subsurface offsets that will be computed during areal-shot migration of PERM data. Implicit to PERM is that reflectors must be identified. 3D Pre-stack interpretation can be cumbersome, but it allows, for instance, avoiding the use of reflectors with low signal-to-noise ratios in migration velocity estimation. In 3D, the size of PERM data can be one order of magnitude smaller if cross-line subsurface-offsets are to be computed. Further data size reduction by one order of magnitude is achieved if the initial conditions are computed with common-azimuth migration.

In addition to the reduced data size, the definition of the velocity model is greatly accelerated due to target-oriented nature of PERM, which allows wavefields to be propagated only in the region where the velocity is to be updated. The 3D example with real data confirms the accuracy of the velocity solution achieved by migration velocity analysis by wavefield extrapolation using PERM wavefields.

Fast 3D velocity updates using the pre-stack exploding reflector model