Numerical Simulation Study On Motion Law Of Sand Deposition In Vertical 90° Elbow Of Oil-Water Pipeline

With the oilfield development,it is inevitable to carry the solid impurities in the formation to the oil gathering and transportation system,and in the multiphase flow pipeline sand content is increasing.Some high sand content of crude oil in gathering and transportation process,while taking several desanding technology,but part of the sand still exist in oil-water pipelines and The system of gathering and transportation crude oil has properties of complex process,much equipment,variability of flow states.Thus including sand,a variety of impurities,such as pipeline corrosion products,insoluble salt in crude may accumulate in the pipeline or separator and other production equipment,causing blockage,accelerate internal corrosion in pipeline.In order to understand the rule of sand deposition in the mixed transportation pipeline,the numerical simulation method is used in this paper.Using Fluent-EDEM coupling method,particles and liquid phase coupling mathematical model is established,selected the particle mechanics model and contact model,and expounds the solving process of discrete element method particle motion equation and the selection of the numerical calculation time step.Through the simulation of solid-liquid two-phase flow pattern simulation to confirm Fluent-DEM coupling method is applied to the simulation of sand deposition in oil-water pipeline.The horizontal-elbow-vertical pipe model was built,and combined with Gudong joint station sand sample data and literature setting simulation parameters.In Fluent software through comparison of various turbulence models then used RNG k-?model to solve liquid phase flow field;In EDEM software used discrete element method with full consideration particle-particle,particle-liquid phase and particle-wall interaction,and then coupled with fluent by Euler method to solve the particles movement in liquid phase flow field.The process of particle deposition and transition to non-deposition state includes:?1?Particle impact wall,?2?A moving bed flow is formed at the bottom of the pipe,?3?The particle movement changed from moving bed flow to stationary bed flow,?4?Particles deposition reaches the state of dynamic balance or increasing thickness and length,?5?After increasing the liquid flow rate,the particles gradually moved away from the edge of stationary bed,forming a suspension flow or moving bed flow,stationary bed disappeared.The premises that particles can be deposited at the elbow:Liquid flow velocity is less than the particle deposition critical velocity with a certain particle characteristics,pipe characteristics and liquid phase characteristics.The influence of particle,pipe characteristics and liquid phase characteristics on the deposition of particles was studied by the control variable method.Got critical velocity V₁ of formation moving granular bed and critical velocity V₂ of stable deposition under different parameters.According to the sand deposition in the pipeline in law,put forward measures and suggestions to prevent sand deposition.