Reservoir simulations of cyclic steam stimulation (CSS) at Cold Lake show that both the oil recovery level, and the efficiency of the process as measured by the oil produced/heat injected ratio (OHR), are independent of steam quality. However, with constant volume (rather than constant energy) injection, the calender day oil rate (CDOR) decreases with a reduction in steam quality. Therefore, the higher the steam quality the more economic the CSS process becomes. Present boiler technology enables a practical maximum of 80 percent quality steam.The study also demonstrates that a temporary reduction in steam quality results in a temporary efficiency gain for the same cumulative energy injection, accompanied by a corresponding drop in CDOR. The reduction has no permanent impact on well performance in the subsequent cycles, since the CDOR rebounds to normal levels after higher steam quality injection is resumed.Leming pilot field data show that an uneven steam quality split resulted in some wells consistently receiving higher quality and others receiving lower quality steam. Nevertheless, analysis indicates that each well still received approximately the same energy due to flow nozzle meter calibration. The net result was no harmful effect on well performance and recovery, consistent with the simulation predictions. As a result, accurate wellhead steam quality measurements are not References and illustrations at end of paper. 463 deemed necessary to further optimize performance.
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