Porous Media Research Group (PORO), Microfluidics Laboratory, Federal University of Santa Catarina, 89219-600 Joinville, SC, Brazil.
Porous Media Research Group (PORO), Scientific Computational Laboratory, Federal University of Santa Catarina, 89219-600 Joinville, SC, Brazil.
Lab Chip. 2022 Nov 22;22(23):4680-4692. doi: 10.1039/d2lc00445c.
Carbonate rocks usually present a wide variation in pore size within a sample and may contain macroscopic pores ranging from a few millimeters to microscopic pores smaller than one micrometer. Therefore, studying the fluid flow inside carbonates presents a challenging problem. This study proposes a methodology to create dual-porosity micromodels for studying single and two-phase fluid flow in multiscale, carbonate-like, rocks. For this purpose, a design technique for Rock-on-a-Chip (ROC) devices based on the Voronoi tessellation was extended to take into account bimodal pore size distributions, allowing the creation of a macroporous system made up of larger channels and vugs that can be filled with distinct microporosity types. The porous media thus generated were then employed to fabricate polymer micromodels by applying the soft lithography technique. Experimental and numerical results show that the microporosity can increase or reduce the permeability, depending on whether it is added to the grains and/or to the large channels. Even when the microporous matrix completely filled the large channels, the addition of vugs did not increase the permeability. Regarding two-phase fluid flow, the location of the steady-state fluids after drainage clearly depends on the proportion and spatial distribution of microporosity, as well as its type. For the micromodel with microporous grains, no significant amount of wetting fluid was displaced from the micropores. In contrast, when microporosities fill the large channels, the injected fluid forces the displacement of the wetting liquid from the micropores, although far from effectively. The novel approach presented in this work represents a step forward in the artificial generation of more representative micromodels for studying fluid flow at the pore scale.
碳酸盐岩通常在样品内呈现出广泛的孔径变化，并且可能包含从几毫米到小于一微米的微观孔隙的宏观孔隙。因此，研究碳酸盐岩内部的流体流动是一个具有挑战性的问题。本研究提出了一种方法，用于创建双孔隙微模型，以研究多尺度碳酸盐岩中单相和两相流体的流动。为此，基于 Voronoi 细分的 Rock-on-a-Chip (ROC) 器件设计技术被扩展，以考虑双峰孔径分布，从而可以创建由较大通道和溶洞组成的大孔系统，这些通道和溶洞可以填充不同的微孔类型。然后，通过应用软光刻技术，将生成的多孔介质用于制造聚合物微模型。实验和数值结果表明，微孔的存在可以增加或降低渗透率，具体取决于其是否添加到颗粒中和/或大通道中。即使微孔基质完全填充了大通道，添加溶洞也不会增加渗透率。关于两相流体流动，排水后的稳态流体的位置显然取决于微孔的比例和空间分布及其类型。对于具有微孔颗粒的微模型，几乎没有润湿流体从微孔中被置换出来。相比之下，当微孔填充大通道时，注入的流体迫使润湿液体从微孔中被置换出来，尽管效果远不理想。本工作中提出的新方法代表了在人工生成更具代表性的微模型以研究孔隙尺度下的流体流动方面迈出的一步。
