Experimental Research on the Effect of Heating Temperature, Demulsifier Dose and Water Cut on the Oil-Water Separation in Three-Phase Separator

The three-phase separator has a wide range of applications in oil production industry. For the purpose of studying the effect of heating temperature, demulsifiers and water content on the separation of oil-water mixture in the three-phase separator, eight kinds of oil samples were taken from different oil transfer stations in Changqing Oilfield and the mixtures were prepared by stirring method. To simulate the two-stage dehydration process, the first stage dehydration experiments without any heating were performed on mixtures at the dose of 100ppm demulsifer at 20°C, and the water cut of these mixtures is the same as that of the gathering pipeline in each oil transfer station. The water cut of the upper crude oil was measured after 40 minutes, and the values of them ranged from 0.5 vol% to 65.2 vol%. No visual stratification was observed for the sample most difficult to separate, so it was selected to conduct the second stage dewatering process. Three bottles of the same mixture were prepared and heated to 30°C, 40°C and 50°C, respectively. The results showed that all of them stratified in 10 minutes, and the water-cut values of the upper oil layer were 1.4 vol%, 0.5 vol% and 0.3 vol%, respectively, compared to 65.2 vol% at 20°C. When the concentration of demulsifier was changed to 200ppm and 300ppm, the results exhibited almost no differences. So it is deduced that the further improvement of heating temperature and demulsifier dose have limited enhancement on oil-water separation. At Last, 35 vol%, 50 vol%, 70 vol% and 85 vol% water cut mixtures of the special oil sample were made to experiment as previously. In consequence, the 35 vol% water-cut emulsions presented a relatively slow rate of oil-water stratification at low heating temperature, and the oil content of the lower separated water was improved by the addition of demulsifier dosage above 100ppm when the water cut was 90 vol%. It is indicated that high heating temperature is necessarry for low water-cut mixtures oil-water separation and can be appropriately reduced to save energy consumption as the water cut continues to rise. The demulsifier dosage is also neccessary be controlled in high water cut period. These experimental data provide the basis for the further optimization operation of the three-phase separator.