毛管压力曲线是模拟岩土非饱和渗流或多相渗流过程的重要本构关系. 在排水过程中,当湿润相饱和度趋近于残余饱和度时,多孔介质中将形成角膜和液桥流动现象. 这种角膜-液桥流对排水条件下毛管压力曲线的影响机制,目前还缺乏深入研究. 本文搭建微流控可视化实验平台, 在6组不同孔隙结构和粗糙度的微流体中开展了准静态排水实验, 实现了多孔介质中角膜-液桥流的细观观测,量化了这一现象对毛管压力曲线的影响. 实验结果表明：角膜-液桥流主要出现在饱和度较低的情况, 将导致湿润相的残余饱和度降低0.21~0.32. 角膜-液桥流的出现与孔隙介质的湿润性密切相关, 粗糙的固相表面会降低湿润相的接触角, 使角膜-液桥流更容易出现. 角膜-液桥的影响与液桥的数量正相关. 随着孔隙率和非均质性的减小, 角膜-液桥流的影响将更显著. 本文研究揭示了多孔介质中角膜-液桥流对毛管压力曲线的影响,对于低饱和度条件下多孔介质毛管压力曲线的理解与表征具有重要的科学意义.

The capillary pressure-saturation curve is the basis for predicting multiphase flow in porous media. As the saturation of the wetting phase decreases, flow through the meniscus and liquid bridges becomes the main mechanism for displacement. However, the understanding of how meniscus and liquid bridges control the capillary pressure-saturation curve is still limited. In this study, we constructed a microfluidic visualization experimental platform and conducted quasi-static drainage experiments in six different microfluidic systems with varying pore structures and roughness. Through the experiments, the phenomena of meniscus-liquid bridge were observed and the influence of this phenomenon on the capillary pressure curve was quantified. The experimental results show that the meniscus-liquid bridge phenomenon mainly occurs at lower saturations and leads to a reduction in the residual saturation of the wetting phase by 0.21 to 0.32. The occurrence of the meniscus-liquid bridge phenomenon is closely related to the wettability of the porous media, where rough solid surfaces decrease the contact angle of the wetting phase, making the meniscus-liquid bridge phenomenon more likely to occur. The impact of the meniscus-liquid bridge is positively correlated with the number of liquid bridges, and as the porosity and heterogeneity decrease, the meniscus-liquid bridge phenomenon becomes more significant. This study reveals the influence of the pore-scale meniscus-liquid bridge phenomenon on the capillary pressure-saturation curve, which is of significant importance for predicting multiphase flow.

TU375.4