Abstract
First break picking involves detecting the onset arrivals of refracted signals from a single
signal source at the individual receiver in a receiver array. First-break picking can be done
manually or automatically. This work outlines the procedures and benefits of automatic picking
from first arrivals using monitor records obtained from reflection survey in Sufyan Oil Field,
Sudan. The first breaking was done using SeisOptPicker. Reliable picking was ensured by
applying linear move out (LMO) to the data before picking. This was reversed after picking.
The length, in milliseconds, of the time window for the automatic picker to look for the first
arrival on a trace was set to a value of 20-ms to accommodate the large distance between the
nearest and farthest offset. The start time search from last first break pick was set at 0
milliseconds. This means that it will not look for the pick at a time earlier than the current pick.
Traces where the first arrival comes in earlier than the preceding trace were rejected. The
results obtained from the automatic picks were compared with results from conventional
refraction survey. The Sufyan prospect Low Velocity Layer (LVL) consists mainly of three
layers from both refraction survey and parameters computed from first break automatic picks
from production survey. The average thickness of first layer obtained from refraction is 20.0m
as against 22.4m obtained from automatic picks. The velocities calculated for these layers are
435m/s and 400m/s from the refraction and automatic picks respectively. The second layer
thicknesses obtained from the refraction survey and automatic picks from production survey
approaches are 52.8m and 50.0m. Their velocities in the same order are 931m/s and 800m/s.
The consolidated layer average velocity calculated from refraction survey and automatic picks
from production survey are 1850m/s and 1848m/s respectively. The LVL parameters obtained
from automatic first break picks from production survey can be used for static corrections in
the Sufyan oil field without conducting dedicated refraction surveys.