ABSTRACT

After water flooding, there is much residual oil left in the pores. This cannot be easily displaced, but polymer flooding is able to achieve this. The use of viscoelastic solutions such as polymer can enhance the oil recovery, because it can increase the sweep volume by improving the mobility ratio of polymer solution and oil. The use of viscoelastic solutions can also increase the displacement efficiency of residual oil in the swept area. This article, based on the momentum equation and Oldroyd-B constitutive model, investigates the influences of polymer solution properties on the stress distribution and deformation of residual oil adhering to the walls of micro-channels. The results show that the elasticity and viscosity of the polymer displacing fluid are the factors with the greatest impact on the stress distribution and deformation of residual oil. The stress computation shows that along the direction of flow, the oil film is compressed at both ends, and pulled in the center. This stress distribution helps the oil film to bulge from its center, leading to its deformation and break-up. Furthermore, by increasing the viscosity or elasticity the residual oil is exposed to greater stress and deformation during the displacement process, which is characterized by a large advancing angle, an increasing deformation index and a small receding angle. Comparison of the simulation and experimental results shows a good conformance. Therefore, to displace the oil more efficiently, the polymer solutions need to be more viscous and elastic, which can be achieved by changing their chemical properties. The results clarify the micro-mechanism of polymers displacing residual oil and quantify the influences of the chemical properties of the solution on the stress, deformation and activation of residual oil.

摘要

注水后，孔中残留了很多残留油。不能轻易地将其置换，但是聚合物驱能够实现这一目标。使用粘弹性溶液（例如聚合物）可以提高油的采收率，因为它可以通过改善聚合物溶液和油的迁移率来增加吹扫体积。粘弹性溶液的使用还可以提高残油在扫掠区的驱替效率。本文基于动量方程和Oldroyd-B本构模型，研究了聚合物溶液性质对粘附在微通道壁上的残余油的应力分布和变形的影响。结果表明，聚合物驱替液的弹性和黏度是影响残余油应力分布和变形的最大因素。应力计算表明，沿着流动方向，油膜在两端被压缩，并在中心被拉动。这种应力分布有助于油膜从其中心凸出，从而导致油膜变形和破裂。此外，通过增加粘度或弹性，在驱替过程中残余油暴露于更大的应力和变形，其特征在于前进角大，变形指数增加和后退角小。仿真和实验结果的比较显示出良好的一致性。因此，为了更有效地置换机油，聚合物溶液需要更具粘性和弹性，这可以通过更改其化学性质来实现。结果阐明了置换残油的聚合物的微观机理，并量化了溶液化学性质对残油的应力，变形和活化的影响。