Geoscience Reference
In-Depth Information
Fig. 2.35
Example of mutes applied during stacking. Here we see two mutes applied to a set of
gathers. The red mute is applied to stop events being distorted by the stretch caused by the normal
moveout process at large offsets and shallow times. The green inner trace mute has been applied to
remove remnant multiples on the near traces that have not been removed by other demultiple
processes such as Radon.
stacked section. For instance, CMP 1 may contain traces 1,5,9
...
, CMP 2 will have
offsets 2,6,10
...
, CMP 3 offsets 3,7,11
...
, CMP 4 4,8,12
...
, CMP 5 will be back
to 1,5,9
This four-trace pattern may be visible in the final section particularly in
the near surface where the fold of data (number of traces stacked together) is low
owing to the stretch mute. Any regularly repeating pattern will show itself as a strong
component in the inline spatial Fourier transform and can be removed by a notch
filter.
Step 25 is a 3-D noise removal process. The application of noise suppression is much
more successful with 3-D data than 2-D owing to the extra dimension, data volume and
spatial consistency for the algorithm to work with. Usually relatively small operators are
used, working on maybe five traces in both directions. This allows the filters to adapt to
relatively sudden changes in reflector dip while retaining sufficient data to distinguish
....
