# Trace density

The number of traces summed into the natural bin in a seismic survey.

## Computing fold

We compute fold F according to the equation[1]

${\displaystyle F={\frac {\pi X_{\mathrm {max} }^{2}}{4SR}}}$

and trace density T using:

${\displaystyle T=F\times {\frac {4}{sr}}\times 10^{6}}$

using the following parameters:

Maximum offset Xmax
the maximum offset recorded in the patch. If this is not known, and you are more interested in the fold at a given depth, then use the target depth instead.
Source line spacing, S
the distance between source lines.
Source interval, s
the distance between the source points along the source lines.
Receiver line spacing, R
the distance between receiver lines.
the distance between the receiver points (sometimes called 'stations') along the receiver lines.

## Seismic quality

Cooper suggests a high-level guide for selecting an appropriate trace density, depending on the imaging problem at hand (modified here, based on oil sands applications):

Traces/km2 Application
< 6000 Not advisable
6000 to 18 000 For simple structure plays with good signal:noise
18 000 to 25 000 For stratigraphic and subtuning plays with good signal:noise
25 000 to 100 000 Increasing as signal:noise deteriorates, or as structural complexity increases
100 000 to 1 000 000 Expensive seismic for worst-case scenarios
> 1 000 000 Very expensive seismic for reservoir development and time-lapse applications

## References

1. Cooper, N (2004), A world of reality: Designing land 3D programs for signal, noise, and prestack migration (Tutorial), The Leading Edge, October and December 2004.