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The Impact of Wettability and Surface Roughness on Fluid Displacement and Capillary Trapping in 2‐D and 3‐D Porous Media: 2. Combined Effect of Wettability, Surface Roughness, and Pore Space Structure on Trapping Efficiency in Sand Packs and Micromodels
Water Resources Research ( IF 5.4 ) Pub Date : 2020-07-23 , DOI: 10.1029/2020wr027965
Bilal Zulfiqar 1 , Hannes Vogel 2 , Yi Ding 1 , Saeed Golmohammadi 1 , Matthias Küchler 3 , Danny Reuter 4 , Helmut Geistlinger 1
Affiliation  

A comprehensive understanding of the combined effects of surface roughness and wettability on the dynamics of the trapping process is lacking. This can be primarily attributed to the contradictory experimental and numerical results regarding the impact of wettability on the capillary trapping efficiency. The discrepancy is presumably caused by the surface roughness of the inner pore‐solid interface. Herein, we present a comparative μ‐CT study of the static fluid‐fluid pattern in porous media with smooth (glass beads) and rough surfaces (natural sands). For the first time, a global optimization method was applied to map the characteristic geometrical and morphological properties of natural sands to 2‐D micromodels that exhibit different degrees of surface roughness. A realistic wetting model that describes the apparent contact angle of the rough surface as a function surface morphology and the intrinsic contact angle was also proposed. The dynamics of the trapping processes were studied via visualization micromodel experiments. Our results revealed that sand and glass beads displayed opposite trends in terms of the contact angle dependence between 5° and 115°. Sand depicted a nonmonotonous functional contact angle dependency, that is, a transition from maximal trapping to no trapping, followed by an increase to medium trapping. In contrast, glass beads showed a sharp transition from no trapping to maximal trapping. Since both porous media exhibit similar morphological properties (similar Minkowski functions: porosity, surface density, mean curvature density, Euler number density), we deduce that this difference in behavior is caused by the difference in surface roughness that allows complete wetting and hence precursor thick‐film flow for natural sands. Experimental results on micromodels verified this hypothesis.

中文翻译:

润湿性和表面粗糙度对二维和3-D多孔介质中流体驱替和毛细管捕集的影响:2.润湿性,表面粗糙度和孔隙空间结构对砂堆和微模型捕集效率的综合影响

缺乏对表面粗糙度和润湿性对捕集过程动力学的综合影响的全面理解。这主要归因于关于润湿性对毛细管捕集效率影响的矛盾实验和数值结果。的差异被推测由引起的表面粗糙度的的内孔-固体界面。本文中,我们对具有平滑表面(玻璃珠)和粗糙表面(天然砂)的多孔介质中的静态流体-流体模式进行了比较μ- CT研究。对于第一次,施加到映射特性的全局优化方法的几何天然砂的形态学特性呈现出不同程度的表面粗糙度的二维微模型。还提出了一个实用的润湿模型,该模型将粗糙表面的视在接触角描述为函数表面形态和固有接触角。诱捕过程的动力学是通过可视化的微观模型实验研究的。我们的结果表明,在5°和115°之间的接触角依赖性方面,沙子和玻璃珠显示出相反的趋势。描述了一个非单调的功能接触角依赖性,即从最大捕获到没有捕获的过渡,然后是增加到中等捕获。相比之下,玻璃珠显示了从无陷阱到最大陷阱的急剧转变。由于两种多孔介质均表现出相似的形态学特性(相似的Minkowski函数:孔隙率,表面密度,平均曲率密度,欧拉数密度),因此我们推断出这种行为差异是由表面粗糙度的差异引起的,该粗糙度允许完全润湿并因此导致前体厚‐天然沙子的膜流。微观模型的实验结果证明了这一假设。
更新日期:2020-09-26
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