1. n. [Enhanced Oil Recovery, Heavy Oil]
A type of in-situ combustion in which the burning front moves in an opposite direction to the injected air. Initially, air is injected into a production well and the fire is ignited. After the burning front has advanced some distance from the production well, air is supplied only near the injection well. The burning front advances toward the injection well while the oil moves toward the production well. Reverse combustion actually refers to dry reverse combustion and can be used to recover extremely viscous oil or tar. In reverse combustion, the liquid blocking problem is solved because a hot zone is maintained near the production well. Despite this advantage, this process is not as efficient as dry forward combustion because lighter fractions of the oil are burned and heavier fractions are left behind the burning front. Another drawback is the possibility of a spontaneous ignition in the injector well, which will divert air for combustion near the injector well instead of near the producer.