SOLVENT ASSISTED STEAM INJECTION PROCESS FOR RECOVERY OF VISCOUS OIL

摘要

F-2524SOLVENT ASSISTED STEAM INJECTION PROCESSFOR RECOVERY OF VISCOUS OILABSTRACTA method for recovery of viscous oil from a subterranean,viscous oil-containing formation employing mixture of steam and 2 to5% of a light solvent having an equilibrium K-value of at least 0.5 atinitial formation temperature and pressure that results in maximumsolvent efficiency based upon the ratio of cumulative oil recovered tothe amount of solvent injected and unrecovered. A predeterminedamount of a mixture of steam and 2 to 5% by volume of a light solventhaving the desired equilibrium K-value is injected into the lower 50%or less of the formation via an injection well and fluids includingoil and a portion of the light solvent are produced from the upper 50%or more of the formation via a spaced-apart production well. Theamount of steam injected is 0.30 to 0.50 pore volume at a temperatureof 500°F to 700°F, a quality of 50 to 90%, and an injection rate of 4to 7 barrels (CWE) per day per acre-foot of formation. Thereafter,production of fluids including oil and light solvent is continueduntil steam breakthrough occurs or until the fluid being producedcontains a predetermined amount of water, preferably at least 95%.The method is applied to a viscous oil-containing formation in whicheither naturally occurring or induced communication exists between theinjection well and the production well in the bottom zone of theformation. Suitable light solvents include C1 to C4 hydrocarbonsand carbon dioxide. In another embodiment of the invention, injectionof the mixture of steam and solvent may be continued and fluidsincluding oil and solvent are produced until steam breakthrough occursor until the water cut of the produced fluid contains at least 95%water.