Effect of gas on separation performance of an axial hydrocyclone for preliminary water separation

Hydrocyclones have become the preferred solution to the high water cut of fluids produced in oil wells. However, the gas associated with these fluids affect the separation efficiency of hydrocyclones. In the present study, the impact of gas on flow field stability and oil-water separation performance of an axial hydrocyclone for pre-liminary water separation was investigated theoretically and experimentally. The results show that small amount of gas enhanced oil-water separation, while large amount impeded it. The oil concentration of the outflow water first decreased and then increased with the increasing gas liquid ratio. The gas liquid ratio corresponding to the inflection point was 5% in slug flow regime and 8% in bubble flow regime. For different split ratios and water cuts, the impact of the GLR on the separation performance followed similar patterns. The gas decreased the oil concentration by 8.8% at most when the GLR was <5%. It decreased the oil concentration by 12.5% at most when the GLR was 7%-30%. The results obtained in this study show the relevant effect of gas in the functioning of hydrocyclones for the preliminary water separation and the importance of the reasonable control of GLR to reduce the impact in the separation performance.