The electroviscous flow of non-Newtonian fluids in microtubes and implications for nonlinear flow in porous media
The electroviscous flow of non-Newtonian fluids in microtubes and implications for nonlinear flow in porous media
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DOI：
10.1016/j.jhydrol.2020.125224
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发表时间：
2020-11-01
影响因子：
6.4
通讯作者：
Dai, Sheng
中科院分区：
文献类型：
--
作者：
Cheng, Zhilin;Ning, Zhengfu;Dai, Sheng
基于电动力学和非牛顿流体流变学理论，对低渗透油藏低速非线性渗流进行了解释。为了实现这一目标，我们模拟的Bingham-Papanastasiou（BP）流体在圆形微管的稳态电粘性流动，同时解决Poisson-Boltzmann和修改的Navier-Stokes方程。考察了毛细管半径R、zeta电位zeta、屈服应力τ（0）、应力增长指数m等因素对非牛顿流体的诱导电场强度、垂直线E-s、速度分布和输运能力的影响。结果表明，BP流体的E-s垂直杆受流体流变性的影响较大，与牛顿流体的E-s垂直杆有很大不同。随着m或τ（0）的增加，速度分布变得更低、更平坦，这在较小的微管中更为显著。非牛顿流体的表观粘度随着c（无穷大）的增加而单调下降，但随着R、m、tau（0）和zeta而非单调下降。此外，当考虑非牛顿流体的动电流动时，可以成功地捕捉到微管中的低速非线性流动。而对于牛顿流体，仅考虑电粘性效应不能产生非线性流动行为。还讨论了电动参数与流变特性对流动非线性程度的贡献。动电参数（zeta，c（无穷大））对流动特性的影响在高压梯度下是显著的，当压力梯度相对较低时变得微不足道。相反，流体流变参数（m，τ（0））极大地决定了在低压梯度下发生的流动非线性的大小。总之，BP流体在微通道中的电粘性流动为多孔介质中低速非达西流动提供了一种可能的解释。
This paper aims to interpret the low-velocity nonlinear flow occurring in low-permeability reservoirs based on the theories of electrokinetic transport and non-Newtonian rheology of fluids. To achieve this end, we simulate the steady-state electroviscous flow of Bingham-Papanastasiou (BP) fluids in circular microtubes by simultaneously solving the Poisson-Boltzmann and the modified Navier-Stokes equations. The induced electrical field strength vertical bar E-s vertical bar, velocity profiles, and the transport capacity of the non-Newtonian fluid under the effects of various factors (such as capillary radius R, zeta potential zeta, yield stress tau(0), and stress growth index m) were examined. The results show that the generated vertical bar E-s vertical bar of the BP fluid is highly affected by the fluid rheology, which is quite different from that of the Newtonian liquid. The velocity profiles become lower and flatter as m or tau(0) increases, and this is more remarkable in smaller microtubes. The apparent viscosity of non-Newtonian fluid declines monotonically with increasing c(infinity), yet non-monotonically with R, m, tau(0), and zeta. In addition, the low-velocity nonlinear flow in microtubes can be successfully captured when considering the electrokinetic flow of the nonNewtonian fluid rheology. While for the Newtonian fluid, only involving the electroviscous effect fails to generate the nonlinear flow behavior. The contributions of electrokinetic parameters versus rheological properties to the degree of flow nonlinearity are also discussed. The impact of electrokinetic parameters (zeta, c(infinity)) on the flow characteristics is significant at high-pressure gradients and becomes trivial when the pressure gradient is relatively low. In contrast, the fluid rheological parameters (m, tau(0)) greatly determine the magnitude of the flow nonlinearity occurring at the low-pressure gradients. In sum, the electroviscous flow of BP fluids in microchannels provides a possible explanation of the low-velocity non-Darcy flow in porous media.