4D vertical seismic profiling (VSP) integrates a baseline 3D seismic survey with followup surveys that allow measuring any changes that have occurred in the survey area. One operator performed steam-assisted gravity drainage (SAGD) to enhance their oil production and called on Schlumberger to use 4D VSP to determine if this method of enhanced oil recovery was the most effective. Schlumberger performed a number of tests, including determining the acquisition footprint, to ensure repeatability and account for errors between the two surveys. After only 9 months of oil production, the teams were able to image the differences in the reservoir before and after SAGD production with excellent repeatability.