Viscous fingering in a partially miscible system in a 2-D micromodel

When a less viscous fluid displaces a more viscous one in porous media, the interface of the two fluids gives a finger-like pattern. This phenomenon is called Saffman–Taylor instability or viscous fingering (VF). VF experiments have been frequently performed by a Hele-Shaw cell. In addition to viscous difference, fluid-fluid miscibility also plays an important role in the VF dynamics. Partially miscible fluid pairs exhibit a phase separation due to its finite solubility into each other. In a previous study, the finger formation in a partially miscible system changes to the generation of multiple droplets by performing VF experiments with a Hele-Shaw cell. Moreover, a numerical simulation of the partially miscible VF in the Darcy model considering phase separation is conducted and the VF pattern transition into a droplet formation pattern is demonstrated. These studies conclude that this VF dynamics is driven by thermodynamic instability such as phase separation due to spinodal decomposition and Kortweg convection induced by compositional gradient. However, experimental investigation on the partially miscible VF in porous media remains unexploited. In this study, we perform VF experiments with miscible, immiscible, and partially miscible systems with a 2D micromodel. We observe droplets with a partially miscible system and we qualitatively and quantitatively find the differences concerning fluid dynamics between miscible, immiscible and partially miscible ones in the micromodel.