Heavy oil recovery

Details Heavy oil recovery Heavy oil recovery

E - Fixed Constructions

21

B

166/39

E21B 43/24 (2006.01) E21B 43/16 (2006.01) E21B 43/243 (2006.01)

Patent

CA 1228533

ABSTRACT The invention discloses a method of producing viscous immobile oil from a subsurface formation. Initially, steam is injected into the formation for a period of time by way of an injection well and a production well. Thereafter, the wells are backflowed to produce fluids from the formation. Production may be preceded by a shut-in period allowing the steam to soak and transfer heat to oil in the formation. This cycle of steam injection followed by backflowing is designed to create voidage in the formation for the second stage of the process. This voidage is needed to permit adequate oxygen injection for the second stage. Thereafter, an oxygen-containing combustion-supporting gas is injected by way of the injection well into the top of the formation to form a fluid conductive path between injection and produc- tion wells. The oxygen combustion-supporting gas must be injected into the top of the formation to accomplish the objectives of this invention. Subsequently steam is injected into the formation, preferably near the bottom of the forma- tion. Steam rises up and then steam and condensed water flow over the oil through the conductive path created in the in situ combustion stage of the process. Heated oil adjacent the top of the formation is produced by steam drag into the producing well or wells. The steam drag of the third stage of the process recovers much more oil than would be produced by conventional steam drive.

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