Real-Time Pore-Scale Investigation of the Effects of Uniform, Random, and Heterogenous Porous Structures on Intrinsic Permeability Using Two-Dimensional Microfluidic Chips

Abstract

Permeability is a significant fluid flow property that is essential for the evaluation of oil recovery methods. The intrinsic permeability of a porous medium is influenced by factors such as the size distribution of pores and pore throats, the connectivity between pores, the topology of the pores, and the geometry of individual pores. Yet, it is not well understood how multiple elements of pore geometry interact to affect permeability due to the complex and heterogeneous nature of porous structures. This study examines the real-time porescale effects of uniform, random, and heterogeneous porous structures on intrinsic permeability, considering the broader complexity of the pore network as a single unit. The intrinsic permeability exhibited a negative correlation with increasing heterogeneity of the porous structure regardless of whether the porosities were the same or different. At a porosity of 0.59, the uniform pattern exhibited a permeability of 4.07 Darcy, while the heterogeneous pattern had a permeability of 2.37 Darcy. The random pattern demonstrated greater permeability (2.57 Darcy) at a lower porosity (0.47) in comparison to that of the heterogeneous network. Pore-scale experiments and simulations have demonstrated the significant influence of the pore network topology on the intrinsic permeability. As the complexity and heterogeneity of porous structures increase, the combined effect of morphological characteristics on intrinsic permeability becomes more significant than the individual influence of each morphological property. The differences in permeability observed in the experiments were attributed to the presence of stagnant water zones, which could be permanent or temporary. Stagnant water is more likely to be permanent in homogeneous patterns than in heterogeneous patterns. Heterogeneity appeared to promote water movement and redistribution because of variations in local pressure due to variations in pore sizes. The presence of dead-end pores in the random pattern led to a slight fluctuation in the experimental permeability. However, this effect was more prominent in the simulated permeability. Our study found experimental and numerical evidence that the broader heterogeneity of the porous structure significantly impacts permeability. Moreover, it highlights the importance of accounting for the actual microscopic porous structure of the reservoir being targeted when microfluidic devices are employed for enhanced oil recovery techniques.