Bed coalescence efficiency of oil separation from formation water was studied on model systems involving 10 real samples of crude oil and its fractions of different characteristics. Oil components were varied and all other parameters were kept constant, and high mineralization water served as the continuous phase. All experiments were realized on a commercial WO/O4 two-stage bed coalescer. Temperature, oil content, and fluid velocity were kept constant for all samples. Model emulsion was dispersed by constant stirring during the experiment to obtain primarily droplets of 20 mu m diameter. Correlations for predicting the coalescence efficiency as a function of some physical and chemical oil properties are presented. The investigated oil components ensured a wide span of viscosity, density, and interfacial tension. The influences of mean molecular weight, neutralization number, as well as the contents of n-alkanes, NSO, and aromatics on coalescence efficiency were analyzed. On the basis of the empirical dependences of coalescence efficiency on individual parameters obtained by regression analysis of the data, a general mathematical model was established.