粘弹性聚合物溶液对残余油膜的作用机理

EFFECT OF VISCOELASTIC POLYMER ON RESIDUAL OIL

针对水驱后残余油膜的存在形式,及油藏孔隙内聚合物溶液粘弹特性,选取具有相继收敛和扩张特性的波纹管模型和广泛用于数值计算粘弹性流体的上随体Maxwell本构方程,建立了由连续性方程、运动方程和上随体Maxwell 本构方程、流函数、涡量函数及边界条件组成的较完整的数学模型。通过有效的数值求解,从力学的角度提出聚合物驱在理论上提高驱油效率的机理是:(1)粘弹性聚合物溶液产生的第一法向应力和剪切应力对油膜的携带作用大于相同粘度的牛顿流体产生的剪切应力对油膜的携带作用,从而可携带部分残余油膜流动;(2)粘弹性聚合物溶液与牛顿流体相比,相同流函数值的流线位置发生改变,其波及范围大于相同粘度的牛顿流体。

Based on the types of residual oil in pore media after water flooding and the viscoelasticity of polymer fluid in reservoir pore, undulating tube model which has the contraction - expansion cyclical process and upper-convected Maxwell model which is generally applied to numerical calculation of viscoelastic fluid areselected. The mathematics model made up of continuity equation, equation of motion,UCM constitutive equation, stream function, vorticity equation as well as the boundary conditions are established. By effective numerical calculation, the mechanism of improving oil displacement efficiency of polymer fluid through mechanical analysis and theories analysis is:(1) the rolling action on oil film by first normal stress and shear stress from viscoelastic polymer fluid is greater than the one by shear stress from Newtonian fluid with same viscosity, residual oil film can flow partly;(2) comparing polymer fluid with Newtonian fluid, the same stream line is not in the same position, and the swept volume of viscoelastic polymer fluid is larger than Newtonian fluid with same viscosity.