Princeton University, Princeton, NJ, 08544, USA.
Small. 2020 Mar;16(9):e1903944. doi: 10.1002/smll.201903944. Epub 2019 Oct 10.
Polymer solutions are frequently used in enhanced oil recovery and groundwater remediation to improve the recovery of trapped nonaqueous fluids. However, applications are limited by an incomplete understanding of the flow in porous media. The tortuous pore structure imposes both shear and extension, which elongates polymers; moreover, the flow is often at large Weissenberg numbers, Wi, at which polymer elasticity in turn strongly alters the flow. This dynamic elongation can even produce flow instabilities with strong spatial and temporal fluctuations despite the low Reynolds number, Re. Unfortunately, macroscopic approaches are limited in their ability to characterize the pore-scale flow. Thus, understanding how polymer conformations, flow dynamics, and pore geometry together determine these nontrivial flow patterns and impact macroscopic transport remains an outstanding challenge. This review describes how microfluidic tools can shed light on the physics underlying the flow of polymer solutions in porous media at high Wi and low Re. Specifically, microfluidic studies elucidate how steady and unsteady flow behavior depends on pore geometry and solution properties, and how polymer-induced effects impact nonaqueous fluid recovery. This work thus provides new insights for polymer dynamics, non-Newtonian fluid mechanics, and applications such as enhanced oil recovery and groundwater remediation.
聚合物溶液常用于提高油藏采收率和地下水修复，以改善被困非水相流体的回收。然而，由于对多孔介质中流动的理解不完整，应用受到限制。曲折的孔隙结构既产生剪切又产生拉伸，从而使聚合物伸长；此外，流动通常处于较大的威森贝格数 Wi 下，此时聚合物弹性又强烈改变流动。尽管雷诺数 Re 较低，但这种动态伸长甚至会产生具有强时空波动的流动不稳定性。不幸的是，宏观方法在表征孔隙尺度流动方面的能力有限。因此，了解聚合物构象、流动动力学和孔隙几何形状如何共同决定这些非平凡的流动模式并影响宏观输运仍然是一个悬而未决的挑战。本综述描述了微流控工具如何揭示高 Wi 和低 Re 下聚合物溶液在多孔介质中流动的物理基础。具体而言，微流控研究阐明了稳态和非稳态流动行为如何取决于孔隙几何形状和溶液性质，以及聚合物诱导效应如何影响非水相流体的回收。因此，这项工作为聚合物动力学、非牛顿流体力学以及提高油藏采收率和地下水修复等应用提供了新的见解。
