Britannica Sources used in this answer

How does forward combustion differ from reverse combustion in heavy oil recovery?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Arabian-Iranian basin oil fields — heavy oil and tar sand Major oil fields of the Arabian-Iranian basin region.

In in situ combustion for heavy oil recovery, the primary difference between forward and reverse combustion lies in the direction of the burning front relative to the air injection and production wells.1

Forward Combustion

In forward combustion, air is injected into a well to advance the burning front away from the injection point. This process heats and displaces both the oil and formation water toward surrounding production wells. A modified version of this technique involves injecting cold water alongside air to recover residual heat from behind the combustion front, which improves efficiency by reducing the required air volume and the amount of oil consumed as fuel.1

Reverse Combustion

Reverse combustion is specifically designed for extremely viscous oils that cannot flow through the cold zones typically found ahead of a forward-combustion front. In this method, a short-term forward burn is initially triggered by injecting air into a well that is intended to eventually serve as the production well. Once ignited, the air injection is switched to adjacent wells, effectively moving the combustion front in a direction that allows the oil to be recovered through the heated zone.1