Optimization of non-ionic surfactants for removing emulsified oil from gas condensate oil–water emulsion in N oilfield

Abstract

The aim of the present study was to obtain effective and economical chemical agents for treatment of oily water from N oilfield. Component characterization of crude oil from N oilfield was carried out with gas chromatography–mass spectrometry. Optimization of non-ionic surfactants combined with dissolved air flotation (DAF) for oil removal was investigated. The results show that the crude oil consisted of nine major components which counted for 96.4% of the total composition, and the first four compounds made up 50% of the total composition. For the first four compounds, the density difference between water and each individual compound is smaller than the difference between water and normal alkanes with the same number of carbon atoms, while the solubility of these four compounds in water is greater than that of normal alkanes with the same number of carbon atoms. The characteristic of both density and solubility of the crude oil increased the oil water separation difficulty in DAF progress. The oil content in oily water from N oilfield without any treatment was 5285.95 mg/L. The oil content after treatment of DAF without any chemicals was 895.53 mg/L. Non-ionic surfactants NIS1, NIS2 and NIS3 all were effective for removing emulsified oil in oily water in DAF progress. 1200 mg/L NIS1 combined with DAF was the optimized formulation by the view of efficiency and economy. The formulation could be successfully used as a commercial product in N oilfield.