Experimental study on the influence of clay particles on the stability of heavy oil emulsions and explanation of the influencing mechanism

Emulsion is of great concern in the process of crude oil production. In the later stages of heavy oil reservoir development, the crude oil produced on the surface exists in the form of emulsion, accompanied by sand production. Some sand particles are transported to the surface with the fluid. It is necessary to determine the mechanism by which the type and size of clay particles affect the performance of emulsions in order to aid in demulsification. Therefore, the effects of different clay particles and sizes on the shape and stability of the emulsion and stability was studied. The research results show that emulsion droplets with added montmorillonite contain more clay particles in their interior compared to droplets with added kaolin and illite systems. The diameter of the droplets in the montmorillonite system is larger and mostly ranges between 10–12 μm. The proportion of droplets with a diameter of 12–20 μm in the kaolin and illite systems is smaller than that in the montmorillonite system. When the same type of clay particles are added, with the increase in particle size, the late-stage water volume and viscosity of the montmorillonite system are the highest. The range of water volume is 6.38–7.3 mL, and the viscosity slightly increases within the range of .07–.66 mPa·s. When the clay particles are 8–10 μm, the viscosity increase of each system also gradually becomes smaller. The molecular dynamics simulation results show that the effects of adding clay particles on the root mean square displacement in different directions are z-axis > y-axis > x-axis. The addition of clay particles in the system has a lower crude oil migration speed compared to the blank system, ranging from .0001 to .0003 Å2/ps. The addition of clay particles mainly affects the root mean square displacement of oil droplets in the vertical direction. Through this study, the effects of different clay particles on the emulsion of heavy oil have been preliminarily determined, providing guidance for the treatment of heavy oil emulsions.