Droplet Crystallization in Water-in-Crude Oil Emulsions: Influence of Salinity and Droplet Size

Ice crystallization in confined spherical geometries is investigated experimentally at ambient pressure conditions. Water-in-crude (w/o) oil emulsions are formed by homogenization of an acidic North Sea crude oil with water or brine, at aqueous phase fractions ranging from 1 to 30 wt % and varying electrolyte contents. Ice-in-oil dispersions are formed from the emulsions by cooling, and they provide a justified analogue to gas hydrate formation in water-in-crude oil emulsions, due to analogous wettability conditions that govern agglomeration. Nuclear magnetic resonance (NMR) spectroscopy and digital video microscopy (DVM) imaging establish droplet size distributions (DSDs) and mean droplet diameters, and demonstrate emulsion stability with an absence of coalescence over extended time durations. Differential scanning calorimetry (DSC) establishes the crystallization temperature of the dispersed water droplets. It is demonstrated that the crystallization temperature decreases with a decreasing length scale of the dispersed water droplet phase, in accordance with theoretical knowledge.