Conclusions
1. Droplet formation observed in the partially-miscible Hele-Shaw
studies is associated with emulsion instability: produced emulsions from
the droplet morphologies require an external mechanical force to
maintain their stability.
2. Emulsion stability is predominantly dependent on the viscosity force.
With the increase in the strength of the viscous force, the number of
droplets decreases. This effect is especially pronounced at the later
stage of the experiment for cases that contain both the surface-active
agent and the viscosifying agent. Surfactant-induced fingers are
consumed by large and highly-stable polymer-induced fingers via the
Ostwald ripening process.
3. Low IFT is associated with the droplet generation after the
initiation of the finger break. The opposite is observed to be true
(less droplet generation) before the finger stability loss (at earlier
stages of the experiment) which implies that low IFT is a leading factor
in hydrodynamic stability at the initial stage. However, upon the
stability loss, droplets are generated and such droplet generation
continues until it begins to plateau.
4. Finger development before and after the stability loss follows
separate self-similarity patterns and such divergence in patterns can be
noted in saturation profiles plotted with the time variable.
5. Fractal dimensions have a proportional relationship with surface
tension and an inversely proportional relationship with viscosity.
6. We presented two types of “self-similar” behaviors per the
categorization based on the saturation profiles. However, certain
complex colloidal samples may display multiple self-similar fingering
behaviors based on the chemical component, mechanism, and subsequently
induced hydrodynamic stability (or instability).
7. For the future study (in oil recovery), the impact of droplet
generation behavior on heavy oil recovery in the porous media can be
investigated. Pore size distribution can be predicted to be the most
significant parameter on the droplet retainment behavior which can
improve the overall oil recovery via entrapment (mobility control), or
reduce it by decreasing the relative permeability to oil.