МЕТОДИКА РАСЧЁТА ТЕЧЕНИЯ НЕФТЕВОДОГАЗОВЫХ СМЕСЕЙ В СТВОЛЕ ВЕРТИКАЛЬНОЙ СКВАЖИНЫ

Abstract

Background The flow pattern of oil-water-gas mixtures («gas - liquid» (two-phase) and «oil - water - gas» (three-phase) mixtures) in vertical production wells is one of the most complex types of liquid-gas flows. At present, the calculation method of a gas-liquid flow where a two-component «oil + water» liquid is considered a homogenous mixture and liquid phase components move with the same velocity (without slipping) has become popular. At the same time, it is assumed that viscosity, liquid phase density and surface tension coefficient of the «liquid - gas» phase change according to the linear law as a function of water cut. Under actual conditions, six flow modes can take place in a vertical well (finely dispersed flow - oil in water, dispersed flow - water in oil, mist flow - oil in water, mist flow - water in oil, dispersed flow - water in oil, and finely dispersed flow - water in oil), depending upon the liquid phase velocity and its component ratio. Each flow mode needs its own approach to determine viscosity, density and surface tension coefficient of the «liquid - gas» phase. Aims and Objectives Lack of published methods of hydraulic calculation of gas-liquid mixtures taking into account different flow modes of liquid phase components witnesses the insufficient state of knowledge of the process. At the same time, there is a demand for a precise calculation of density and viscosity of liquid phase of oil-water-gas mixture flows and flow calculation methods for vertical wellbores to complete a number of practical tasks associated with designing oil production equipment, which is the scope of discussion in this paper. Results A calculation method for oil-water-gas mixtures (two-phase «liquid - gas», and three-phase «oil - water - gas») for bubbly, plug and annular flow modes of liquid-gas mixtures in vertical wells has been developed. The method is most appropriate for calculating pressure in low-rate wells with high water production. Results of analyzing the impact of adjusted calculations of water-oil flow upon the parameters of oil-water-gas mixture in vertical production tubing are listed. It was established that using liquid component slipping mechanism in the calculation method for the bubbly gas-liquid flow with a dispersed (oil in water) structure of the liquid phase provides a means for specifying pressure performance along the production tubing from 0.5 % to 8.0 % of production water cut values.