# Welcome to Techco Geophysical Services Ltd.

## Developing seismic processing software

Main Software Products - PHASE SHIFT DEMIGRATION

__PSDMIG__ uses a single velocity function to demigrate a 2D or 3D stack. The result of this process is a stack where diffractions have been restored and horizons have been shifted back to their premigration locations. One possible use for this algorithm is to perform a "better" poststack depth migration. The following processing flow could be used:
1) Run a DMO process out to common offset ranges.

2) Poststack migrate each of these offset ranges using a single time varying
velocity function. This will reposition horizons to locations which are
more accurate than the unmigrated result.

3) Sort into cdp gathers and perform velocity analysis.

4) Stack the data using the new velocity field.

5) Demigrate the data using the same single velocity used in the poststack
migration. The result is a better stack.

6) Perform poststack depth migration.

Poststack depth migration frequently doesn't yield an optimal result simply
because the stacking process has destroyed data. If one can generate a better
stack, one would expect a better result from poststack depth migration.

Last modified: Tue Sep 2 20:59:57 MDT 2003