Capillary Trapping Following Imbibition in Porous Media: Microfluidic Quantification of the Impact of Pore‐Scale Surface Roughness
Capillary Trapping Following Imbibition in Porous Media: Microfluidic Quantification of the Impact of Pore‐Scale Surface Roughness
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DOI：
10.1029/2019wr025170
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发表时间：
2019-11
影响因子：
5.4
通讯作者：
A. Mehmani;Shaina Kelly;C. Torres‐Verdín;M. Balhoff
中科院分区：
文献类型：
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作者：
A. Mehmani;Shaina Kelly;C. Torres‐Verdín;M. Balhoff
由于成岩作用，地下岩石（如砂岩）中的孔隙以自生胶结物涂层和矿物溶解的形式表现出不同程度的表面粗糙度。先前描述多孔介质中毛细管捕获的工作主要集中在孔隙空间几何形状、润湿性和流体粘度对比度上，同时承认但未量化表面粗糙度的潜在影响。我们介绍了一种方法来实现表面粗糙度的控制变化的小丘的密度和高度到玻璃微流控芯片，并调查表面粗糙度的影响，气体捕获后吸胀的水到空气中。我们证明，表面粗糙度与小丘高度孔深比（在本文中称为Ω）小于介质依赖性阈值（微观模型中Ω = 6%-10%）不会促进非润湿相（气体）捕获。相比之下，Ω值大于上述粗糙度阈值的粗糙微观模型显示出捕获气体饱和度的急剧增加（气体饱和度值高达64%），这是由于观察到的自吸动力学变化，从二元填充到孔喉内的摆动环形成以及孔体内的毛细管钉扎。此外，当将微模型中间毛细管数结果与Land的模型进行比较时，只有最粗糙的微流体芯片（Ω > 10%）落入文献描述的特征捕获常数C的值内，这意味着表面粗糙度也是关键的气体捕获控制，独立于或除了孔隙空间几何形状和润湿性之外。提出了一种先验的接触角稳定性准则和基于局部接触角变化的启发式解释来解释表面粗糙度引起的捕获。
Due to diagenesis, pores in subsurface rocks such as sandstones exhibit varying degrees of surface roughness in the forms of authigenic cement coatings and mineral dissolution. Previous work describing capillary trapping in porous media has primarily focused on pore‐space geometry, wettability, and fluid viscosity contrast, while acknowledging, but not quantifying, the potential impact of surface roughness. We introduce a method to implement surface roughness with controlled variation of hillock density and heights into glass microfluidic chips and investigate surface roughness impacts on gas trapping following imbibition of water into air. We demonstrate that surface roughness with hillock height‐to‐pore‐depth ratios (herein called Ω) less than a media‐dependent threshold (Ω = 6%–10% in the micromodels) does not promote nonwetting phase (gas) trapping. By contrast, rougher micromodels with Ω values larger than the aforementioned roughness threshold show a dramatic increase in the saturation of trapped gas (gas saturation values up to 64%) due to an observed change in imbibition dynamics from binary filling to pendular‐ring formation within pore throats as well as capillary pinning within pore bodies. Furthermore, when the micromodel intermediate capillary number results are compared to Land's model, only the roughest microfluidics chips (Ω > 10%) fall within the literature‐described values of the characteristic trapping constant, C, implying that surface roughness is also a key gas trapping control, independent of or in addition to pore‐space geometry and wettability. An a priori menisci stability criterion and a heuristic explanation based on local contact angle variations are proposed to explain surface roughness‐induced trapping.