This study describes
how varying oil/water contents affect emulsion
formation and the impact they have on emulsion droplet size, viscosity,
and interfacial behavior. Crude oil (continuous phase) volume fractions
of 40, 50, 60, and 70 vol % were probed in the various W/O emulsions
formed. Experimental results from optical morphology revealed the
emulsion droplets kept reducing as the crude oil fraction kept increasing,
while the droplets were nearly unnoticeable in the emulsions derived
from 60 and 70% crude oil. The viscosity–shear rate of emulsions
produced from 40, 50, and 60 vol % crude oil exhibited a non-Newtonian
behavior owing to the substantial volume of water content in their
emulsions, whereas the viscosity–shear rate of the emulsion
with 70 vol % crude oil exhibited a Newtonian behavior similar to
the pure crude oil, suggesting a thorough blending of oil–water
at this crude oil fraction. Besides, the viscosity–temperature
measurements revealed that the viscosity of these emulsions diminished
as the temperature increased and the viscosity reduction became more
noticeable in an emulsion comprising 70 vol % crude oil. In the interfacial
assessment, the increased crude oil content in the produced emulsion
led to a sharp reduction in the interfacial tension (IFT). The IFT
values after 500 s contacts between the emulsion and water (surrounding
phase) were 11.86, 10.02, 8.08, and 6.99 mN/m for 40, 50, 60, and
70 vol % crude oil, respectively. Demulsification experiments showed
that water removal becomes more challenging with a large volume of
crude oil and a small water content. Demulsification performances
of the lab-grown nonionic demulsifier (NID) after 10 h of demulsification
activity at room temperature (25 °C) were 98, 90, 17.5, and 10%
for the emulsions formed from 40, 50, 60, and 70 vol % crude oil,
respectively, indicating that the demulsification degree decreases
with an increasing crude oil content. Viscosity–time determination
was applied to affirm the activity of NID on the emulsion formulated
with a 50% crude oil fraction. The injection of NID in this emulsion
triggered a sharp viscosity reduction, indicating the adsorption of
NID at the oil–water interface and disruption of emulsifiers,
enabling emulsion stability.