Separation of water from water-in-heavy-oil (W/O) emulsions has been a costly problem. Due to the high viscosity of heavy oil, increasing the temperature of the emulsion has been one of the most common methods of separating water from W/O emulsions. The other methods include adding demulsifiers and using coalescence media. For the treatment of water in oil emulsions, providing a strongly water-wet coalescing media is the key for the coalescence of water droplets when the oil is the continuous phase. Laboratory tests and field applications have shown that use of the coalescence media can significantly improve the oil-water separation efficiency by reducing demulsifier concentration, treatment temperature, and residence time of the emulsion stream in separators. Various pack materials and methods have been tested for coalescence media by many researchers with no success due to the fact that water-wet material packed in a coalescence column is not able to remain water-wet in a heavy oil environment.
In this study the principle of capillarity and the mechanism of wetting film in porous media are applied in designing the coalescence media. Water-wet porous particles are used for the first time in the coalescing column to enhance the separation of water form water-in-heavy-oil emulsions. Experimental results of this study show this type of particles can remain water-wet in an oil environment and can significantly enhance the coalescence of water droplets in water-in-heavy-oil emulsions. The coalescing column test results show that the flow of the emulsion through the 10 cm coalescing column reduced water content from 44.37% to 21.54% (51% reduction) at 80oC, without using demulsifier. This result indicates that the coalescing column is effective in helping water droplets coalesce. The results also demonstrate that the coalescing column can reduce the water content beyond what was reached in gravity separation with a high dosage of demulsifier. At a fixed temperature of 80oC, and with a settling time of 4 hours, when the dosage of the selected demulsifier changed from 50 to 100 to 150 ppm, water content reached 10.49%, 1.32% and 0.64%, respectively, with the use of a 10 cm coalescing column. Using the coalescing column reduced water content in the heavy oil by 38%, 89%, and 93%, compared to the water contents reached in the separation with demulsifier dosages of 50, 100, and 150ppm, respectively, without using the column. These results indicate that the effect of adding a coalescing column to water separation is significant, as compared to just using a demulsifier in gravity separation. More importantly, flow through the coalescing column could reduce the water content in the heavy oil to a very low level (<1.0%) and, at the same time, reduce the consumption of demulsifier.