Reservoir simulation of injection and production well geometries for parallel horizontal wells with varied steam injection schedules was used to investigate recovery from primary production, displacement and gravity drainage processes. This revealed that the recovery following primary depletion is improved by placing the injector close to the top of the formation and the producer near the bottom. Once the steam chamber between injector and producer is formed and continuous, the gravity drainage mechanism becomes dominant. This regime is described as SAGD and the oil production is insensitive to steam injection rate.
The utilization of all three recovery stages results in 22-56% recovery with cumulative SOR of 4-5. The economic analysis (sensitive to specific oil/steam prices and discount factor) revealed that following primary depletion with the low rate drainage processes (SAGD) provided no increase in NPV over continuing primary production until the economic limit is reached. Following primary depletion with a higher rate displacement process on the original pattern or smaller pattern areas increased the NPV significantly.