The study gas multistage separation at the preliminary preparation of crude oil by means of computer simulation was performed. Different models have been used as the phase state equations in HYSYS software: Peng-Robinson, Grayson-Street-Choa-Seeder, Peng-Robinson-Twu, Suave-Redlich-Kwong, Twu-Sim-Tassone. The carry-over saving of liquid oil components into off gases approximately is 40–60% while optimizing thermobaric conditions of the separation was obtained. The semi-empirical model obtained on the basis statistical processing of the results of laboratory experiments was proposed. The proposed semi-empirical model has a slight deviation for the first and the second separators. There is a negative effect in the third separator, but it is not significant in comparison with the positive effect in the first and the second separators.

The transition from water-in-oil to oil-in-water emulsion is generally very abrupt and it is characterized by a marked decrease in the effective viscosity. The mathematical model of the ascending bubble in the water phase comparatively to the oil phase is described in this paper. Numerical simulation has been performed on two petroleum compositions with different water cut using HYSYS software. More even distribution of gas evolution for multistage separation has been obtained with water cut of oil approximately 75%. These results allow saving of heavy hydrocarbons due to reducing of entrainment into off-gases.

This paper presents the results of a detailed study of the separation process in the range of characteristic values temperature (Т ≅ 0 ÷ 70 °C) and pressure (P ≅ 50 ÷ 700 kPa). The critical analysis of hydrocarbonaceous media separation process problem is made within functioning processing equipment on objects of the “Vyngapurovskoe” oil field in Russia. Modelling of first stage separation process is illustrated from data of reservoir fluid with detailed characteristic of evolution some components concentration into off-gas in dependence of temperature and pressure. Recommendations to the calculation of the component composition of hydrocarbonaceous fluids under the provisions of equilibrium thermodynamics using the model of Peng-Robinson are extradited. It has been established that the heavy hydrocarbons (С4+higher) concentration decreasing into off-gas theoretically could be achieved up to 48.41%.

In this paper the features of separation processes modelling are analyzed in hydrocarbonic media within the limits of thermodynamics of equilibrium states. Approaches to calculation of phase equilibrium in multicomponent systems are discussed. Regularities and peculiarities of composition change of gas mixture depending on the temperature and pressure are studied. It has been established that there are specific conditions of non-monotonic change of composition with extremums for some separation regimes that significantly influences the physical properties and intensity of exchange processes at the heat-and mass transfer in multicomponent hydrocarbon media. In addition, the details of the behavior of gas phase with changing its thermal and physical properties have been discussed. Also, the calculated distributions of Prandtl, Schmidt and Lewis-Semenov numbers essentially influencing on the intensity of transport processes are considered.