Geoscience Reference
In-Depth Information
coefficients or with large velocity contrasts (such as sub-salt plays in the Gulf of
Mexico) is an area of active development within the geophysical industry. Recently
introduced wave equation methods are based on the prediction of the multiple from the
primary location. These techniques show considerable promise but they are expensive
compared with moveout techniques and do not easily lend themselves to true 3-D im-
plementation owing to acquisition limitations. Currently they are applied to data in a
2-D sense and fail if there is a strong cross-dip component in the multiple-generating
surface.
2.5.4
Binning
Data binning is the process where every trace is assigned to midpoint locations (i.e. a
location halfway between shot and receiver). To achieve this the survey area is covered
by a large number of rectangular bins as shown in
fig. 2.28
. Traces are then assigned
a Common Midpoint (CMP) location at the centre of the bin in which they fall. In
marine acquisition, if the streamers were perfectly straight behind the boat, all the
bins would contain a regular sampling of offsets, which would be highly desirable for
seismic processing. However, because of feathering this is not the case. In particular, the
Planned CDP lines
Original bin based on regular geometry
Fig. 2.28
Data binning. The size of the bins is determined by the original acquisition. The bins are
centred on the planned locations with width equal to the CMP (also known as CDP) spacing and
length equal to the line spacing.
