| 摘要 |
A steam flooding method for recovering oil from an underground formation penetrated by an injection and at least one production well is modified by initially lowering the permeability of the lower vertical portion of the formation, e.g., by plugging thereof with gravel sand pack, capped by a plaster of paris or cement, thereafter continuing to inject the steam into the injection well and maintaining high level of production from the production well until thermal breakthrough is achieved in the production well. Subsequently, the initial permeability of the lower vertical portion of the formation is restored, e.g., by removing the gravel sand pack, and oil is recovered from the production well. In a preferred embodiment, the permeability of substantially the entire initial completed interval of the production well is decreased in the aforementioned manner, the well is recompleted higher in the formation and steam is continuously injected into the injection well. Subsequently, the secondary completed interval is plugged, and the permeability of the primary completed interval is restored substantially to its original level. The method of the invention decreases the time necessary for thermal breakthrough in the production well, thereby accelerating thermal communication between the injection and the production wells and improving vertical sweep efficiency of the cyclic steam or steam flooding methods of heavy oil recovery.
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