E - Fixed Constructions – 21 – B
Patent
E - Fixed Constructions
21
B
166/33
E21B 43/20 (2006.01)
Patent
CA 1228021
F-2529 SOLVENT ASSISTED STEAM INJECTION PROCESS FOR RECOVERY OF VISCOUS OIL ABSTRACT A method for recovery of viscous oil from a subterranean, viscous oil-containing formation employing a mixture of steam and solvent in specific amounts and specific solvent equilibrium K-values at initial formation temperature and pressure to attain maximum solvent efficiency based upon the ratio of cumulative oil recovered to the amount of solvent injected and unrecovered at steam breakthrough. For a light solvent, maximum solvent efficiency is obtained by injecting a mixture of steam and 2 to 5 volume % solvent having an equilibrium K-value of at least .5 into the formation. Suitable light solvents include C1 to C4 hydrocarbons and carbon dioxide. For a medium solvent, maximum solvent efficiency is obtained using a mixture of steam and 5 to 10 volume % solvent having an equilibrium K-value within the range of .005 to .5. Suitable medium solvents include C5 to C9 hydrocarbons, naphtha and natural gasoline. For a medium heavy solvent, maximum oil recovery is obtained using a mixture of steam and at least 10 volume %, and preferably 10 to 15 volume % solvent having an equiliorium K-value within the range of .00005 to .005. Suitable medium heavy solvents include C10 to C14 hydrocarbons, light crude and syncrude. The mixture of steam and solvent is injected into the lower 50% or less of the formation via an injection well and fluids including oil and a portion of the solvent are produced from the upper 50% or more of the formation via a spaced-apart production well. The amount of steam injected is 0.30 to 0.50 pure volume at a temperature of 500°F to 700°F, a quality of 50 to 90%, and an injection rate of 4 to 7 barrels (CWE) per day per acre-foot of formation. Thereafter, production of fluids including oil and light solvent is continued until steam breakthrough occurs or until the F-2529 fluid being produced contains a predetermined amount of water, preferably at least 95%. The method is applied to a viscous oil-containing formation in which either naturally occurring or induced communication exists between the injection well and the production well in the bottom zone of the formation. In another embodiment of the invention, injection of the mixture of steam and solvent may be continued and fluids including oil and solvent are produced until steam breakthrough occurs or until the water cut of the produced fluid contains at least 95% water.
467975
Hartman Kathy J.
Shu Winston R.
Gowling Lafleur Henderson Llp
Mobil Oil Corporation
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