Discussion
Despite the availability of a large quantity of literature on viscous fingering (immiscible and miscible), few have addressed the viscous finger types that involve chemical interaction. And emulsion flow—especially that of heavy oil has been mostly neglected. In this paper, we attempt to address this missing gap by approaching emulsion flow through fractal analysis and quantification analysis using various dimensionless numbers. Based on this analysis, we have provided the phase map to describe the overall relationship with hydrodynamic stability, surface tension, and viscosity using the original experimental images. The fractal dimension (DB) corresponding to each image has also been provided (Figure 18 ). It can be inferred that tip-splitting like behavior is associated with miscibility at low viscosity conditions (and higher fractal dimensions). In this emulsion flow study, with the hydrodynamic stability loss, droplet formation begins until it eventually reaches the steady-state of energy and droplets maintain their shape. The mechanism for the temporary or permanent halt in the coarsening process in the case of surfactant-induced fingering requires further investigation—-although CMC may be suspected to be the cause. In the case of fingering induced by surfactant and polymer, viscosity plays a significant role in maintaining the hydrodynamic stability, and surfactant-induced fingers develop before the development of the polymer-induced fingers (which also have higher hydrodynamic stability)— which eventually results in the consumption of surfactant-induced fingers by polymer-induced fingers via Ostwald ripening. Polymer-induced fingers are characterized by a smooth frontal mobility line along with a high level of hydrodynamic stability subsequently rendering droplet generation non-existent.