DATUMING AND DEPTH MIGRATION

Datuming is a method of processing to extrapolate a known wavefield at a specified datum of arbitrary shape to another specified datum, also of arbitrary shape. Often, people think of datuming as a different process than migration. Since most migration schemes are performed by wavefield extrapolation followed by imaging, the datuming is done implicitly during the migration process. The migration process usually does not save any wavefield during the extrapolation because its intended output is the subsurface image.

Examining the relations between the inputs and outputs of datuming and migration operators (Figure ) helps to understand their similarities. The input to the datuming operator is a wavefield on a specified datum and the output is a wavefield on another datum. The datuming operator is an extrapolation operator in either the depth or the time direction. The migration operator has more components: the imaging and the transformation operators, because it requires the output to be the subsurface image and the image space differs from the data space.

The direction of wavefield extrapolation can be either time or depth. We confine our discussion to depth extrapolation methods using phase shift in this paper.

 

dtimg
Figure 1 Schematic comparison between the datuming and the depth migration in the input and the output relations.