Influence of inorganic solid particles on the stability of water-in-crude oil emulsions: Evaluating the role of surface charge

This study examines the effect of inorganic solid particles on the stability of water-in-oil (W/O) emulsions formed during the transportation, refining, and storage of crude oil. The surface properties of inorganic particles, such as kaolinite and calcite, can influence the interface between crude oil and water, affecting the stability of the emulsion. The study evaluates the quantitative effect of these particles on emulsion stability and investigates how surface properties affect the emulsions. Emulsions were prepared using crude oil and synthetic brine, with calcite and kaolinite added as inorganic solid particles. Adding inorganic solids increased the volume of released water and altered the emulsion stability, with high concentrations decreasing the formation of stable emulsions. The dissolution of inorganic solids increased the pH of the solution and promoted demulsification due to the high surface potential of crude oil. The solid particles enhanced the formation of oil-in-water-in-oil (O/W/O) emulsions, generating unstable emulsions. The study also found that increasing temperature and adding inorganic solids decreased the emulsion height over time, which was predicted by the emulsion layer growth model. The coagulation rate constant was a tuning parameter, with a higher value implying higher internal repulsion and stronger coagulation between water droplets, facilitating emulsion instability. It has been observed that elevating the storage temperature and introducing kaolinite accelerates the coagulation rate constant, whereas the addi- tion of calcite decreases this value, ultimately contributing to the stabilisation of the emulsions.