Abstract
Incremental economic analysis of using a demulsifier to enhance the efficiency of a three-phase separator was carried out. This was done because the current produced oil contains more water content than the design specification of the three-phase separator which resulted in experiencing separation inefficiency. Therefore, an injection system was installed so that a demulsifier could be injected to increase the rate of phase separation. In addition, two functional 3-in. outlet water pipes were replaced with 4- and 6-in. pipes to compensate for the third non-operational 3-in. outlet water pipe. This was to ensure adequate and timely discharge of the separated water. The results showed that, with highest used demulsifier concentration, the crude oil content in the separated oil phase increased from 67.4 to 85.5%, 78.5 to 98.1% and 88 to 99.9% respectively in the 3, 4 and 6-inch water outlet pipe diameters respectively. Regarding the economic benefits, the discounted incremental pay back periods at different demulsifier concentrations ranged from 3.14 to 3.94 days, 2.29 to 4.18 days and 2.47 to 5.86 days for 3-, 4- and 6-in. water outlet pipes respectively. The incremental net present value at different demulsifier concentrations ranged from about $10.7 to $29.2 million, $18.6 to $29.9 million and $17.3 to $17.6 million for 3-, 4- and 6-in. water outlet pipes respectively at the end of the 10-year operation. Similarly, the rate of return on incremental investment also ranged from 8,356 to 10,486%, 9,587 to 14,387% and 5,623 to 13,369% for 3-, 4- and 6-in. water outlet pipes. Overall, all the used profitability indicators showed that the retrofit has high economic viability.

Key words: Three-phase separator, retrofit, economic analysis, profitability indicators, demulsifier