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A systematic numerical modeling study of various polymer injection conditions on immiscible and miscible viscous fingering and oil recovery in a five-spot setup
Fuel ( IF 7.4 ) Pub Date : 2018-11-01 , DOI: 10.1016/j.fuel.2018.05.115
Abhijit Chaudhuri , R. Vishnudas

Abstract Polymer flooding is employed to prevent immiscible viscous fingering between oil and water. If the polymer injection concentration is decreased rapidly, there is a high chance that fast growing miscible viscous fingers will pierce through the polymer bank and enter the oil bank. This is very detrimental to oil production. We performed numerical modeling of polymer flooding in one-quarter of a five-spot system. Due to the nonuniform flow field in a five-spot setup, the fingering patterns are very different and miscible fingers are more detrimental in this case than in a rectangular domain. In this paper we quantify the impact of injection concentration and duration of polymer flooding on the growth rate of miscible and immiscible viscous fingers. Besides decrease and increase of immiscible and miscible viscous finger growth at the front and rear of polymer banks respectively, we have shown that the residual oil saturation decreases for higher injection concentrations. However for high injection concentrations, polymer should be injected for a long duration so that the width of the polymer bank is large and miscible fingers cannot cause short-circuiting. Since injection at constant concentration for a long duration is not optimal, simulations for different multi-step injection were performed. Our results demonstrate that arbitrary decreases in polymer injection concentration are not effective for enhancing oil recovery. The ideal polymer injection scheme suggested by our simulations should involve an initial constant rate, followed by a gradual decrease. This is mainly to overcome the retardation due to adsorption of the polymer.

中文翻译:

在五点设置中对不混溶和混溶粘性指法和采油的各种聚合物注入条件的系统数值模拟研究

摘要 聚合物驱用于防止油水间发生不混溶的粘滞指法。如果聚合物注入浓度迅速降低,快速增长的混溶粘性手指很有可能会刺穿聚合物库并进入油库。这对石油生产非常不利。我们在五点系统的四分之一中进行了聚合物驱的数值模拟。由于五点设置中的非均匀流场,指法模式非常不同,在这种情况下,与矩形域相比,可混溶指更有害。在本文中,我们量化了注入浓度和聚合物驱持续时间对混相和非混相粘性指状体生长速率的影响。除了分别在聚合物带的前部和后部不混溶和混溶的粘性指状生长的减少和增加之外,我们已经表明,残余油饱和度随着注入浓度的增加而降低。然而,对于高注入浓度,聚合物应注入较长时间,以便聚合物库的宽度较大且混溶指不会导致短路。由于长时间以恒定浓度注射不是最佳的,因此对不同的多步注射进行了模拟。我们的结果表明,聚合物注入浓度的任意降低对于提高石油采收率是无效的。我们的模拟建议的理想聚合物注射方案应该包括初始恒定速率,然后逐渐降低。
更新日期:2018-11-01
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