(66b) Effect of Particle Wettability on Mineral Oil-Distilled Water Emulsion Stability

The Petroleum industry encounters stable oil-water emulsions during the transportation of production fluids. The presence of natural solid nanoparticles and other surface-active agents is the main reason for the generation of the emulsions with a certain degree of stability. The aim of this study is to experimentally analyze and understand the effect of nanoparticles with different wettabilities, namely, hydrophilic and hydrophobic, on the stability of mineral oil-distilled water emulsions.

To study the effects of nanoparticles on separation kinetics of toil-water dispersions, a Portable Dispersion Characterization Rig (P-DCR) is used, which enables creation of emulsions under different stirring rates. The experiments are conducted with mineral oil and distilled water as model fluids and spherical silica nanoparticles of 20 nm mean size with hydrophilic and hydrophobic wettability characteristics. Experiments are conducted with two particle concentrations of 0.01% and 1% by weight, and all data are collected with the same rotational speed, 600 RPM. In order to consider the effect of initial dispersed phase volume fraction on the emulsion stability, three water cuts of 25%, 50% and 75% are selected.

Firstly, the emulsions are prepared with hydrophobic nanoparticles, which are initially dispersed in the oil phase. The results confirm that highest emulsion stability is obtained with 25% water cut, and only oil creaming occurs. The emulsion is very resistant to water sedimentation and coalescence. The data also show that the rate of separation improves with increasing water cut percentage. The second phase of experiments includes the effect of hydrophilic particles, where the particles are initially dispersed in the water phase. The data demonstrates that in contrast to the hydrophobic particles, fast separation occurs at 25% water cut, and increasing the water cut results in a slower oil creaming process. Emulsions with a combination of hydrophilic and hydrophobic particles are the last phase of this study. The data demonstrate that similar behavior as hydrophobic particles only are observed, which emphasizes dominant effect of the hydrophobic particles compared to hydrophilic ones. The experimental data for all cases show that increasing the particle concentration leads to more stable emulsions.