Tsakiroglou C D, Theodoropoulou M, Karoutsos V, Papanicolaou D, Sygouni V
Institute of Chemical Engineering and High Temperature Chemical Processes-Foundation for Research and Technology Hellas, Stadiou Street, Platani, P.O. Box 1414, 26504 Patras, Greece.
J Colloid Interface Sci. 2003 Nov 1;267(1):217-32. doi: 10.1016/s0021-9797(03)00635-0.
The pore scale mechanisms and network scale transient pattern of the immiscible displacement of a shear-thinning nonwetting oil phase (NWP) by a Newtonian wetting aqueous phase (WP) are investigated. Visualization imbibition experiments are performed on transparent glass-etched pore networks at a constant unfavorable viscosity ratio and varying values of the capillary number (Ca), and equilibrium contact angle (theta(e)). Dispersions of ozokerite in paraffin oil are used as the shear-thinning NWP, and aqueous solutions of PEG colored with methylene blue are used as the Newtonian WP. At high Ca values, the tip splitting and lateral spreading of WP viscous fingers are suppressed; at intermediate Ca values, the primary viscous fingers expand laterally with the growth of smaller capillary fingers; at low Ca values, network spanning clusters of capillary fingers separated by hydraulically conductive noninvaded zones of NWP arise. The spatial distribution of the mobility of shear-thinning NWP over the pore network is very broad. Pore network regions of low NWP mobility are invaded through a precursor advancement/swelling mechanism even at relatively high Ca and theta(e) values; this mechanism leads to irregular interfacial configurations and retention of a substantial amount of NWP along pore walls; it becomes the dominant mechanism in displacements performed at low Ca and theta(e) values. The residual NWP saturation increases and the end WP relative permeability decreases as Ca increases and both become more sensitive to this parameter as the shear-thinning behavior strengthens. The shear-thinning NWP is primarily entrapped in individual pores of the network rather than in clusters of pores bypassed by the WP. At relatively high flow rates, the amplitude of the variations of pressure drop, caused by fluid redistribution in the pore network, increase with shear-thinning strengthening, whereas at low flow rates, the motion of stable and unstable menisci in pores is reflected in strong pressure drop fluctuations.
研究了牛顿型润湿水相（WP）对剪切变稀非润湿油相（NWP）的不混溶驱替的孔隙尺度机制和网络尺度瞬态模式。在恒定不利粘度比以及不同毛细管数（Ca）和平衡接触角（θe）值下，对透明玻璃蚀刻孔隙网络进行可视化吸渗实验。地蜡在石蜡油中的分散体用作剪切变稀的NWP，用亚甲蓝染色的聚乙二醇水溶液用作牛顿型WP。在高Ca值时，WP粘性指进的尖端分裂和横向扩展受到抑制；在中等Ca值时，主要粘性指进随着较小毛细管指进的生长而横向扩展；在低Ca值时，出现由NWP的水力传导未侵入区隔开的毛细管指进的网络跨越簇。剪切变稀NWP在孔隙网络中的迁移率空间分布非常广泛。即使在相对较高的Ca和θe值下，低NWP迁移率的孔隙网络区域也通过前驱体推进/膨胀机制被侵入；这种机制导致不规则的界面构型，并使大量NWP沿孔壁滞留；它成为在低Ca和θe值下进行驱替的主导机制。随着Ca增加，残余NWP饱和度增加，最终WP相对渗透率降低，并且随着剪切变稀行为增强，两者对该参数变得更加敏感。剪切变稀NWP主要被困在网络的单个孔隙中，而不是被困在被WP绕过的孔隙簇中。在相对较高的流速下，由孔隙网络中流体重新分布引起的压降变化幅度随着剪切变稀增强而增加，而在低流速下，孔隙中稳定和不稳定弯月面的运动反映在强烈的压降波动中。
