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.