Research On Oil-water Two-phase Flow Characteristics Of Light Crude Oil Pipeline

Pipeline transportation is the most important way to transport light crude oil at present.The corrosion problem of pipeline is becoming more prominent.The internal inspection data and corrosion product analysis show that the serious corrosion mostly occurs at the bottom of the low position of pipes.The characteristics of internal corrosion are related to the water accumulation.The presence of water will accelerate internal corrosion and threaten the safe operation of pipelines.In this paper,water accumulation in upward inclined pipeline of light crude oil is analysed.By theoretical analysis,flow loop experiment and numerical simulation,the characteristics of oil-water two phase flow are studied.As a result,the critical condition of oil carrying water is determined and corrosion caused by accumulated water is controlled.A large-scale experiment loop was conducted to analyse the flow characteristics and the critical parameters by using a series of transparent acrylic bends with different inclination angles.ICEM-CFD software was used to establish geometric models with different inclination angles and diameters.Based on the flow characteristics and simulation experience of crude oil-water two phase flow,a reasonable 3D Fluent numerical calculation model was selected.Based on grid independence study,the mesh generation method with different diameters was determined.The simulation results were validated by comparing with the typical experimental results.Based on the principle of dichotomy and the single variable controlling,a series of numerical simulation of oil-water two phase flow under different flow rate,viscosity,diameter and oil-water ratio were carried out.Data post-processing was carried out by using Tecplot software.The characteristics of oil-water two phase flow in light crude oil pipeline are analysed,and the law of critical inclination angle of oil carrying water is determined.The experiment and simulation results show that the backflow effect of water phase is the primary cause that water tend to accumulated at the bottom of the pipe.The critical inclination angle increases with the flow rate increases,viscosity increases and pipe diameter decreases,while the oil-water ratio has no influence.By the similarity criterion,the dimensionless number Ya is proposed to analyse the critical inclination angle,and the mathematical model is fitted by MATLAB software,whose precision is over 88%.The numerical simulation of OLGA software is carried out based on the profile and operating condition of XD crude oil pipeline.The calculation results of water accumulation are in agreement with the prediction results by the mathematical model,which is verified combined with the internal corrosion and 21 feature points of XD crude oil pipeline.Based on the mathematical model,the critical inclination angle of oil carrying water in different operation conditions can be determined and the possible location of water accumulation can be judged,which provides scientific basis and engineering guidance for predicting the pipeline corrosion area.