Droplets Interface Refreshment in a Crude Oil Emulsion

摘要

Crude oil is often produced with accompanying water from the oil reservoir. Emulsion is created during production when pressure gradients over choke valves introduce sufficiently high mechanical energy input to disperse water as small droplets in the oil phase. Such water-in-oil emulsions have to be resolved before the oil can be further processed and sold.Chemical treatment is a common method for breaking brine-crude oil emulsions. The principle is to inject molecules that have a stronger affinity with water than the natural surfactants present in the crude oil and that are also more mobile; the demulsifier chemical will remove natural surfactants from the water oil surface but will not be able to resist to the forces between two approaching water droplets. This technique, however, is not always effective because the demulsifier chemical formulation must be adapted to the natural surfactants present at the water-oil interface. To improve the chemical treatment of emulsions, it is therefore useful to have an understanding of other factors that may contribute to emulsion stability.The purpose of this work is to evaluate the feasibility of changing the stability of a water-in-oil emulsion by redistributing the emulsion interface through stirring and the simultaneous addition of fresh water.The emulsion chosen was a very stable brine and Arabian Medium crude oil emulsion produced in Saudi Arabia. The stability of this emulsion is due to the interaction of particular aromatic acids with the asphaltenes in the crude oil. As this forms a skin-like interface between the brine droplets and the crude oil continuous phase, droplets coalescence is prevented.Previous experimental work on this produced water-oil emulsion, where mechanical mixing was performed while adding a low dosage demulsifier chemical, did not provide evidence of decreased emulsion stability compared with the effect of injecting the same demulsifier chemical at the same dosage but without mixing. Therefore, we rearranged the experiments to add 10% of ultrapure water in the emulsion sample, and then determined the water content after mixing.