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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