The effect of sand on the stability of heavy oil emulsions

Opacity interferes with the direct observation of the demulsification of heavy oil emulsions promoted by sand particles. According to measurements of asphaltene adsorbed on the surface of mineral particles (quartz and alginate) by Fourier transform infrared spectroscopy (FTIR), some academics speculated that these particles adsorb asphaltene on an oil/water interfacial film, which destroys the strength of the oil/water interfacial film and promotes the coalescence and settling of water droplets, thus achieving demulsification and delamination. However, this mechanism cannot explain some of the phenomena observed in our experiments. In this study, bottle experiments, rheology tests, and wettability tests were carried out, the results were combined with van Oss theory and liquid bridge theory, and the mechanism by which sand promotes the demulsification of heavy oil emulsions was identified. The polar component of the surface energy of water is much greater than that of oils; as a result, water has better immersion wetting effect on quartz than oils, causing water to preferentially wet sand particles. When sand particles are small, and water droplets are large, the droplets completely wet and encap-sulate the sand particles. When this occurs, the specific gravity of water droplets encapsulating sand particles increases and the settling speed of the water droplets is accelerated. This is the main reason why sand particles promote demulsification of heavy oil emulsions, which has been verified in this study by sand deposition ex-periments in white oil.