Geoscience Reference
In-Depth Information
Fig. 3.11
Time slice display.
because reflectors dip through them more or less gradually and therefore do not have
the distinctive character seen in vertical sections, and partly because there is no direct
information on which way the reflectors are dipping. Close comparison with vertical
sections is needed to identify the reflectors, and most workstation software has the
ability to make composite displays of a time slice and an intersecting vertical section in
order to achieve this easily. When looking for subtle stratigraphic features (e.g. channel
systems) it is often helpful to make 'horizon slices' by slicing through the volume
parallel to a picked horizon (which might for instance be the nearest easily picked loop
above the level of interest). In these slices, the effect of structural dip is more or less
removed, so a cleaner picture of the stratigraphic features is obtained.
3.2.2
Manual horizon picking
The process that is used for interpreting 2-D seismic using paper copies of sections is
as follows. On the paper copies, horizons of interest are picked using pencils, generally
with different colours for different horizons. Picks are transferred from line to line at
intersections by folding one section and overlaying it on the other. Faults are marked up
in the same way. When all the data have been picked, the TWT values to the horizons
are read off the sections at a series of locations (e.g. every 10th CDP) and posted on a
