| 摘要 |
The vertical conformance of a steam drive process is improved and steam override reduced by utilizing a solvent push-pull process in the lower portion of the formation adjacent the production well. Steam is injected into the injection well with production of fluids from the production well. The production well contains two flow paths from the surface, the first being in fluid communication with the upper portion of the formation. Production is continued until there is a water breakthrough from the formation via the first flow path in the production well. After production via the production well is terminated, a predetermined amount of solvent is injected into the lower portion of the formation via the second flow path in the production well while continuing to inject steam into the injection well. After the slug of solvent has been injected, production is immediately resumed by recovering fluids including solvent and oil from the formation via the second flow path in the production well until the amount of solvent in the produced fluid has decreased to a value less than 12 percent by volume. The sequence of solvent injection followed by fluid production is continued for a plurality of cycles until there is water breakthrough at the production well.
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