Migration of the data

We restricted ourselves to 2D anisotropic migration velocity estimation and to mild dips. For that reason, we selected a line where crossline and inline dips are limited (Line 750 illustrated in Figure ). As illustrated, the geologic structure along line 750 is relatively flat, and the assumption of flat reflectors is reasonable. This allows us to use the analytical expression of the RMO in ADCIGs presented by Biondi (2005b) and to compute anisotropic velocity spectra. Furthermore, it has the advantage of having a nearby well. This gives us useful vertical velocity constraints when building the anisotropic velocity model.

In our estimation procedure, we use an anisotropic source-receiver migration program and first perform an isotropic migration of the data starting from the interval vertical velocity model developed by CGG (Figure ). The migration result is illustrated in the Figure .

 

Section-iso-750
Figure 10 Line 750: Migration result obtained after isotropic source-receiver migration.

 

Velocity-750
Figure 11 Line 750: Starting isotropic interval velocity model obtained by CGG (2003).