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