Analysis Of Characteristics Of Multi-phase Flow In Parallel Pipelines System Of Oil Transfer Station

Parallel pipeline flow distribution non-uniform problem widely exists in the oil field oil and gas gathering and transferring system.The uncertainty of the flow of the fluid system in the oil transfer station leads to the generation of the parallel pipeline bias.The phase state and flow state of the flow in the pipeline vary with the pressure and the shape of the pipe,which leads to the inability of the fluid to get into each separator evenly.Determined by establishing the mathematical model of multiphase flow system parallel pipeline flow distribution uniformity the main factors,such as the flow liquid mode of oil transfer station,the distance between the parallel branch pipelines,the inlet flow rate,the gas flow rate and liquid water content of the incoming flow.In this paper,the numerical simulation method is used to study and analyze the fluid flow in the liquid transfer system of the oil transfer station.In view of the actual pipeline system flow distribution problem,the structure of the physical model is reasonably simplified,and the pre-processed ICEM software is used to establish the parallel calculation model of the pipeline system with different influencing factors and the mesh is divided.The tetrahedron unstructured grid is adopted.Four calculation models for symmetric arrangement of radial liquid-level pipe,axial-to-liquid-level pipe,symmetrically-arranged radial-liquid second-level pipe and axial second-floor pipe are established,respectively.The fluid dynamics software FLUENT was used to simulate the three-phase fluid flow of oil and gas in parallel pipes of different calculation models under the same working conditions.The results show that the optimal model with the weakest "biased flow" phenomenon is the calculation model of the symmetrically arranged radial liquid secondary pipe layout method.The best branch spacing for determining the optimal model is about 2.4m.With the increase of inflow velocity,the phenomenon of “biased flow” in parallel pipelines tends to decrease.The increase of gas flow rate in the incoming flow can increase the uniformity of gas phase distribution in parallel pipes with multi-phase flow.When the gas content is greater than 40%,the phenomenon of “biased flow” in parallel pipes is very weak.The uniformity of flow distribution in multi-phase flow parallel pipelines fluctuates with the increase of liquid water content,but the fluctuation range decreases.When the liquid water content is greater than 70%,the “bias flow” phenomenon of the pipeline is very small.The uniformity of the gas distribution in the pipeline increases with the increase of the liquid water content.According to the results of the numerical simulation,the liquid transfer system for the transfer station is designed to arrange the parallel pipes of the radial secondary pipe to be symmetrically arranged.It also proposes the control method of “bias flow” working conditions of the liquid system of the oil transfer station in different production periods,which provides a theoretical basis for the actual production in the field.