Influence of Inorganic Solid Particles in the Formation and Stability of Crude Oil Emulsion

Water-in-oil (W/O) emulsion could be formed during the transportation, refining, and storage of crude oils. In the stockpiling tanks, the emulsion and sludge formation were observed by storing of crude oils for a long period of time and cleaning of tanks. It has been reported that the presence of solids affects the emulsion types as well as the stability of emulsions produced. In addition, the surface properties of inorganic particles could influence the crude oil/water interface and thus affect the crude oil-water emulsion stability. Therefore, in this study, the presence of inorganic solid particles on the formation and stability of emulsion was quantitatively evaluated. A crude oil and synthetic brine were used for emulsion evaluation. In addition, calcite and kaolinite were selected as inorganic solid particles. Emulsions were prepared by mixing crude oil and synthetic brine at a ratio in volume of 1:9. The prepared emulsion was allowed to rest for 24 h and then centrifuged to separate crude oil and water. The volume and pH of resolved water were measured to assess emulsion stability in the presence of inorganic solids. It is found that the addition of inorganic solid particles increased the volume of resolved water and destabilize the emulsion compared to that of without inorganic solid particles. The concentration of solids influences the formation of stable emulsion: high concentration decreases the stable emulsion formation. The dissolution of inorganic solids increases the pH of the water and promotes the demulsification due to high surface potential of crude oil. Moreover, the solid particles enhance the formation of oil-in-water-in-oil (O/W/O) emulsion and thus generates unstable emulsion. Increase of temperature and addition of inorganic solids decrease the emulsion height, which was predicted by emulsion layer growth model where coagulation rate constant was a tuning parameter. High value of the coagulation rate constant implies strong coagulation between water droplets and facilitate emulsion instability.