Influence of key parameters on crude oil desalting: An experimental and theoretical study

Abstract

Desalting plants are often installed in crude oil production units in order to remove water-soluble salts from an oil stream. Experiments in both the laboratory and field have shown the desalting process parameters to be very complicated.This research reflects the results of a study conducted regarding the impact of operational desalting parameters, including the effects of temperature, injected chemicals and the pH of the crude oil associated water, on an electrostatic desalter on one of the oil platforms owned by the Iranian Oil Offshore Company in the Persian Gulf. The temperature range applied was between 98 to 133°C, at which the effects on water and oil density as well as salt efficiency and Basic Sediment & Water (BS&W) were studied. The results demonstrate that for high desalting efficiency a temperature between 115 to 120°C is required. In order to determine which demulsifier provides optimum conditions, the functions of various demulsifiers (noted as C, D, E, F, G and H) on a water–oil emulsion were tested in the laboratory, with C and F providing the optimum output. Accordingly, the field test utilized these two selected demulsifiers. Injection of 50 to 100ppm demulsifier produced optimum separation of 88% for BS&W and approximately 99% for salt. Furthermore, the effect of pH of the crude oil in the water–oil emulsion samples was tested in the laboratory and a suitable range determined to be between 9 and 12.Theoretical calculations utilizing fuzzy logic were performed. These showed satisfactory agreement between the experimental and theoretical results obtained.