Abstract: A horizontal production well is located in the lower portion of a heavy viscous oil-bearing reservoir. A vertical injection well is located in the upper portion of the reservoir. Oxygen-enriched gas is injected down the injector well and ignited in the upper portion of the reservoir to create a combustion zone that reduces viscosity of oil in the reservoir as the combustion zone advances downwardly toward the horizontal production well, the reduced-viscosity oil draining into the horizontal production well under force of gravity.

Abstract: A production well penetrating a subsurface oil-bearing formation utilizes perforations in well casing through which formation fluids enter the well. Production tubing extends from the surface of the earth to a position below such perforations. A pump is positioned at the lower end of the tubing for pumping the formation fluids upwardly through the tubing to the surface of the earth. An agitating unit is positioned below the pump and is rotated in the formation fluid within the well to insure that formation fines entrained in the formation fluids are fluidized for production to the surface of the earth rather than settling out of the formation fluids within the well.