粘弹性流体驱替残余油微观力计算

为进一步探索聚合物的弹性对残余油的驱替机理， 选取上随体 Maxwell 本构方程， 建立粘弹性流体在微孔道中的流动方程。在应力张量理论基础上， 计算作用在残余油膜上的水平偏应力差。分析、 对比不同流变性流体、 油膜宽度及压力梯度对作用在残余油膜上的水平偏应力差的影响。结果表明： 在油田生产实际平均压力梯度为 0.02 MPa/m 的情况下， 水、 幂律流体 （ n = 0.6 ） 、 粘弹性流体 （ We= 0.3） 三者作用于残余油膜上的水平偏应力差的比值约为 1：10：25， 即粘弹性流体 （ We= 0.3） 驱油时对油膜的驱动力大约是水驱的25 倍。进一步从理论上证明了粘弹性流体能够提高微观驱油效率这一结论。

Micro-Force Calculation in Residual Oil Displacement by Viscoelastic Fluid

To further explore the displacement mechanism of flexibility of the polymer to the residual oil， upper-convected Maxwell constitutive equation is selected， and flow equations of the viscoelastic fluidflow in porousroad are established. The horizontal deviatoric stress difference on the residual film iscalculated on the basis of thestress tensor theory. The impacts of the different rheological fluid， thewidth of oil film， and pressure gradient onthe horizontal deviatoric stress difference on the residualfilm are analyzed and compared. The results show that：When flooding with water， power law fluid（n = 0.6） and viscoelastic fluid（We= 0.3） ， the ratio of horizontalde-viatoric stress difference on the residual filmis about 1：10：25 at actual oil production mean pressure gradient of0.02 MPa/m， which means that the driving force of viscoelastic fluid（We = 0.3）on the film is about 25 timesthe water flooding. This innovative conclusion that the microscopic displacement efficiency can be improved byviscoelastic fluids is further proved theoretically.