Department of Chemical Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India.
Soft Matter. 2019 Feb 27;15(9):2057-2070. doi: 10.1039/c8sm02114g.
Capillary driven displacement of viscous liquids into a porous matrix plays a significant role in several porous media applications such as fractured oil reservoirs and paper micro-fluidic devices. The inherent heterogeneity in porous media is known to cause the invading fluid front to lead in narrow pores followed by large pores during spontaneous imbibition. Here, we use experiments in a layered porous medium to show that the leading front is not always in the narrow pores. We observe in a two layered porous medium that the fluid front always advances faster in the narrow pores. However, in a multi-layered porous medium, the front displacement is strongly dependent on the arrangement of the layers, the relative difference between the capillary pressure, the permeability of the layers, and the viscosity ratio of the wetting and the non-wetting fluids. We also develop a one-dimensional lubrication approximation model based on the experimental observations, which predicts the imbibition dynamics in the layers seen in the experiments. Additionally, from our model, we present a scaling law governing the leading front in the porous layers. We also predict using our model that the volume imbibed in the layered porous medium cannot be determined by using the effective porous medium properties and a detailed knowledge of the characteristics of the layers is required to accurately predict the overall imbibition of the layered porous medium.
粘性液体在多孔介质中的毛细驱动置换在许多多孔介质应用中起着重要作用，例如裂缝油藏和纸张微流控装置。众所周知，多孔介质中的固有非均质性会导致侵入流体前缘在自发吸入过程中首先进入狭窄的孔隙，然后进入较大的孔隙。在这里，我们使用分层多孔介质中的实验表明，前缘并不总是在狭窄的孔隙中。我们在两层多孔介质中观察到，流体前缘在狭窄的孔隙中总是更快地前进。然而，在多层多孔介质中，前缘位移强烈依赖于层的排列、毛细压力的相对差异、层的渗透率以及润湿和非润湿流体的粘度比。我们还根据实验观察结果开发了一个一维润滑近似模型，该模型预测了实验中观察到的层间吸入动力学。此外，根据我们的模型，我们提出了一个控制多孔层中前缘的标度律。我们还通过模型预测，使用有效多孔介质性质无法确定分层多孔介质的吸液量，需要详细了解层的特征才能准确预测分层多孔介质的整体吸液量。
