This
study presents in situ visualization of the emulsification/demulsification
of asphaltene-stabilized water-in-oil emulsions using microfluidic
devices. Monodisperse water-in-oil emulsions were generated using
a T-junction, and droplet coalescence was analyzed further upstream
of the collision chamber. The state of aggregation of asphaltenes
contained in the model oil was found to strongly affect the stability
of the emulsions. The aqueous phases used in this study contained
either surfactant (C12–15E7) or microemulsion
with and without demulsifiers. Different demulsifiers and their concentrations
were observed to dramatically affect the coalescence rate. The dilatational
surface viscoelasticity properties were also measured using a pendant
drop tensiometer. Surprisingly, no correlation was found between the
dilatational surface viscoelasticity response and the coalescence
rate of the water-in-oil emulsions.
This article presents a comparison
of the efficiency of d-limonene to other solvent-based microemulsions
(MEs) for the removal
of asphaltene deposits using a dual-permeability porous media microfluidic
device. The dynamics of removal of the deposited asphaltenes were
analyzed using optical microscopy and in situ pressure-drop measurements.
All MEs tested showed a higher asphaltene removal efficiency when
compared to the control ME formulation, a surfactant package without
a solvent. The amount and rate of asphaltene removal were strongly
dependent on the type and amount of solvent contained within the ME.
The dynamics of the asphaltene removal for the most effective formulations
were fit to a pseudosecond-order desorption kinetic model. The results
support a mechanism wherein the MEs solubilize the asphaltene deposits.
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