SWLGS Luncheon Topics
Updated Apr. 4, 2008
April 4, 2008
Seismi Migration: Time or Depth? Kirchhoff or Wave Equation
By Jianhua Pan, Arcis Corporation, Alberta, Canada
Migration is an important step in the seismic data processing workflow. Over the last couple of decades, many techniques have been developed for both time and depth migration. In general, there are two families of migration methods, Kirchhoff and wave equation.
There are many differences between time migration and depth migration. The most obvious difference is the output display of the migrated traces. Beside, time migration has a single output that is the image. The imaging velocity (rms velocity) it produces does not have any physical meaning. However, depth migration generates a dual output, i.e. the image as well as the interval velocity. Part of this talk will show differences between time and depth migrations from the point of view of the algorithms used and also in terms of the application on real seismic data.
As regards migration methods, Kirchhoff method is still very popular in our industry, though the wave equation technique is widely accepted and applied. Since both methods have their own advantages and disadvantages, it may not be advisable to comment on which is better. The Kirchhoff method is accepted as main method for time migration as it affords the convenience of being able to directly use rms velocity. For depth migration, Kirchhoff method is used for velocity analysis and wave equation method is used for final migration. There are some obvious questions that come to mind, the foremost one being: can the wave equation method be applied for time migration with rms velocity and for velocity analysis in depth migration? This talk will not only answer this question but also show some basic concepts as well as differences of Kirchhoff and wave equation methods. This would certainly help in deciding on the particular migration that needs to be adopted for your seismic data.
Jianhua Pan received MS and Ph. D degrees in mathematics from Beijing University of Sciences and Technologies, Beiging, China (1988) and Memorial University of Newfoundland, St. John's, Newfoundland, Canada (2001), respectively. He worked as a lecturer at the Chinese University of Petroleum, Beiging (1988-1996) and did a postdoc at the Mathematical Financial Lab., University of Calgary, Calgary, Canada 1999-2000. After that he worked as a Geophysical Applications Developer at Matrix Geosciences Ltd., Calgary, Canda 2000-May 2001. His latest job is as a Seismic Depth Imager/Software Developer for Arcis Corporation, Calgary, Canada.