FIELD: crude oil treatment. SUBSTANCE: in particular, invention concerns profound dehydration and desalting of stable emulsions of high- viscosity oils with high content of suspended impurities. Preparation method comprises mixing surfactant with polysaccharide, in particular galactomannan. Demulsifier also contains cellulose ether or polyacrylamide at weight ratio surfactant/polysaccharide/(cellulose ether or polyacrylamide) = (0.05- 2.0): (0.01-1.0):(0.001-0.9). Resultant mixture is supplemented by modified starch at weight ratio surfactant/galactomannan/(cellulose ether or polyacrylamide) = (0.05-2.0): (0.01-1.0): (0.001-0.9): (0.1-3.0) and further by stabilizing additive, notably potassium sorbate and/or sodium benzoate, observing weight ratio surfactant/galactomannan/(cellulose ether or polyacrylamide)/modified starch/(sodium benzoate or potassium sorbate) = (0.05-2.0):(0.01-1.0): (0.001-0.9): (0.1-3.0): (0.001-0.5) or surfactant/galactomannan/(cellulose ether or polyacrylamide)/additive = (0.05-2.0): (0.01-1.0):(0.001-0.9): (0.001-0.5). Advantageously, thus obtained demulsifier is dissolved to concentration 0.061 to 7.4 wt % in water or in mixture of water with glycols at vigorous stirring in mixer, preferably in mill-type mixer. Composition is added to emulsion preliminarily dissolved, e.g. in water, at vigorous stirring in mill-type mixer. EFFECT: increased efficiency of demulsifier for high-viscosity oil emulsion. 6 cl, 25 ex
