Pore scale dynamics underlying the motion of drainage fronts in porous media
Pore scale dynamics underlying the motion of drainage fronts in porous media
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DOI：
10.1002/2014wr015916
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发表时间：
2014-11
影响因子：
5.4
通讯作者：
F. Moebius;D. Or
中科院分区：
文献类型：
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作者：
F. Moebius;D. Or
多孔介质中的流体驱替锋面表现出一种特殊的二元性；看似规则的前锋宏观运动是由大量不规则的孔隙尺度界面跳跃推动的。这些孔隙尺度事件形成了突现的前沿形态，影响了前沿后面的相捕获，并可能对前沿的胶体动员和溶质分散起着重要作用。我们介绍了一项实验研究，重点是利用高速相机和快速毛细压力测量来研究排水流体通过烧结玻璃微珠的前沿入侵动力学，以解决在广泛的边界条件(流量和重力影响)下的孔隙尺度入侵事件。我们区分了三种类型的“孔”：由图像分析得出的几何孔洞；在置换过程中成像的单个孔洞侵入体积；以及由恒定抽出速率期间的毛细血管压力波动得出的孔洞体积。对于缓慢的排水速率，所产生的孔隙体积分布非常相似。侵入的孔隙体积不受重力的影响，然而，随着粘性力的增加(驱替速率越高)，小的侵入体积的比例增加。毛细血管压力波动呈指数分布，与先前研究的结果一致。压力波动的分布表现出明显的截止点，与同时发生的入侵事件同时发生。这项研究突出了“气孔”的不同表现及其对外部(宏观)边界条件的敏感性。几何空间和压力空间的显著相似性为动态地推断孔隙大小分布提供了机会。
Fluid displacement fronts in porous media exhibit a peculiar duality; the seemingly regular macroscopic motion of the front is propelled by numerous and irregular pore scale interfacial jumps. These pore scale events shape emergent front morphology, affect phase entrapment behind a front, and are likely important for colloidal mobilization and solute dispersion at the front. We present an experimental study focusing on drainage fluid front invasion dynamics through sintered glass beads using a high‐speed camera and rapid capillary pressure measurements to resolve pore scale invasion events over a wide range of boundary conditions (flow rates and gravitational influences). We distinguished three types of “pores”: geometrical pores deduced from image analyses; individual pore invasion volumes imaged during displacement; and pore volumes deduced from capillary pressure fluctuations during constant withdrawal rates. The resulting pore volume distributions were remarkably similar for slow drainage rates. Invaded pore volumes were not affected by gravitational forces, however with increased viscous forces (higher displacement rates) the fraction of small invaded volumes increased. Capillary pressure fluctuations were exponentially distributed in agreement with findings from previous studies. The distribution of pressure fluctuations exhibited a distinct cutoff concurrent with the onset of simultaneous invasion events. The study highlights the different manifestation of “pores” and their sensitivity to external (macroscopic) boundary conditions. The remarkable similarity of geometrical and pressure‐deduced pore spaces offers opportunities for deducing pore size distribution dynamically.