Pre-Stack Time Migration
We use our proprietary pre-stack Kirchhoff time migration algorithm, PSTM3D, to image both PP and PS data for both 2D and 3D datasets. The flexibility of the Kirchhoff algorithm in terms of ordering and density of input and output makes it ideal for the migration of land seismic data. Commonly we migrate COV ordered data so that azimuthal analysis, such as VVAZ, can be carried out with data in the migrated position. As well, we can migrate to fixed offset bins or to “accordion” bins where offset spacing varies to accommodate natural fold variations.
We migrate both land and marine data with PSTM3D. For land data, we typically migrate from the topographic surface at which the data were acquired. Marine data is migrated from the sea surface.
Velocities for pre-stack time migration velocities are determined using our proprietary interactive velocity analysis software. Velocities can be optimized by examining migrated stacks, migrated gathers or both stacks and gathers simultaneously. In addition to velocities we can also estimate eta which can correct for observed VTI anisotropy or “hockey sticks”. Flattening the far offsets is important for subsequent AVO analysis. Additionally, we can apply 4th and 6th order corrections based on the vertical variation of the migration velocities.
The efficient parallel implementation of PSTM3D, adapted to our in-house clusters of CPUs, ensures optimal turnaround time for even the largest projects.