1. Measurements In Time and In Depth
Seismic - Time Units
Log - Depth Units
Surface Elevation
SHOT
REC’R
Kelly Bushing
Elevation
Base of Weathering
SLIDE 5
This slide illustrates the differences in measurements between seismic and well data
For seismic data, measurements are usually referenced to a common surface elevation (typically sea level) and are recorded in units of two-way travel time
Zero time is when a shot is fired
We then measure the time it takes for the acoustic energy to travel down to a reflection surface and back up to the receiver at the surface
For well/log data, measurements are made relative to a device on the drill rig called the Kelly Bushing (kb)
Depths are in feet or meters along the well bore
If the well is not purely vertical, then we differentiated between ‘measured depth’ and ‘true vertical depth,’ which has to be computed
Depth
Vertical depth
Two-way time
Measured
Courtesy of ExxonMobil
L 7 – Well-Seismic 1