Abstract: At the late stage of steam soaking, the reservoir pressure is low, so is the oil saturation within the wellbore area, while the water cut is high and the ratio of oil to gas low, which means the reservoir production get worse. Nitrogen injection is an ef-fective way to improve oil recovery at late stage of steam soak-ing, which increases the steam soaking volume and provides dis-
placement energy to reduce residual oil saturation and enhance recovery. The results from reservoir simulation indicated that it is reasonable to inject nitrogen first and then steam at late steam soaking, and there exists an optimum nitrogen volume in a in-jection cycle.

Key words: heavy oil reservoir, steam soaking, injecting nitrogen, numerical simulation