Introduction
Since Saffman and Taylor’s (1958) pioneering study, it has become a well-established notion that when a low viscosity fluid displaces a high viscosity fluid, viscous fingering results owing to fluid mechanical instability. Even though there is a lack of consensus on the mechanisms that determine the viscous fingering behavior at reservoir conditions (Settari et al. 1977), it is an effective mechanism that dominates the displacement efficiency; this domination might be more critical with complex fluids such as emulsions, colloids, foam, and reactive chemicals than with simpler structures (fluid pairs) causing purely immiscible and miscible interaction. Therefore, studying viscous fingering is essential in developing a deeper insight into the complex multiphase flow behavior in porous media (Jackson et al. 2017).
Traditionally, fully miscible or immiscible fluid systems are employed to observe these fingering pattern morphologies to understand the physical phenomena of multi-phase flow (Fu et al. 2017). However, in that process, a large quantity of fluid systems in the gap (Figure 1 ) between these two extreme cases of immiscibility (Chuoke et al. 1959; Chen 1989; Ferer et al. 2004; Naderi and Babadagli 2011) and miscibility (Nittmann et al. 1985; Yortsos 1988; Tan and Homsy 1992; Gharbi et al. 2001; Nagatsu et al. 2007; Bischofberger et al. 2014; Chui et al. 2015) was not appropriately addressed.