Geoscience Reference
In-Depth Information
Figure 4.40.
Common-depth-point
(CDP) reflection profiling.
In this example, eight
geophones () record
each shot (
). In (a), shot
Aisfired and a reflection
from a particular point P
on the reflector (the
interface between the two
layers) is recorded by
geophone 8. In (b), all the
geophones and the
shotpoint have been
moved one step to the
right, and shot B is fired;
the reflection from point P
is recorded by geophone
6. Similarly, a reflection
from P is recorded (c) by
geophone 4 when shot C
is fired and (d) by
geophone 2 when shot D
is fired. The four
reflections from point P
can be stacked (added
together after time
corrections have been
made). In this example,
because there are four
reflections from each
reflecting point on the
interface (fewer at the two
ends of the profile), there
is said to be four-fold
coverage. Alternatively,
the reflection profile can
be described as a
four-fold CDP profile.
P
P
P
P
