基于稠密离散相模型的冲缝筛管冲蚀数值模拟研究

Research on the Numerical Simulation of Calking Screen Erosion Based on Dense Discrete Phase Model

针对压裂返排过程中固体颗粒引起的冲缝筛管冲蚀问题,分析颗粒近壁面冲蚀行为,为井下防砂工具的冲蚀研究提供依据。利用计算流体力学方法,基于稠密离散相模型,编写用户自定义函数UDF,研究高砂质量分数下撞击壁面的数目、速度和角度等颗粒的运动特性。通过冲蚀速率增长率的变化确定临界冲蚀流速。结果表明,在压裂返排过程中,颗粒撞击速度随着入口流速的增加而增加,是引起冲蚀速率增加的主要原因。入口流速从6 m/s增加到12 m/s时,孔眼出口处的冲蚀速率最大值从3.54×10^(-2)mm/kg增长到3.42×10^(-1)mm/kg,增长9.66倍;颗粒撞击角度随着流速增加不发生变化;砂质量分数增加,导致入口处颗粒数量增加,颗粒撞击频率也增加,颗粒平均撞击速度更低,速度波动幅度增大,同时颗粒平均撞击角度波动幅度较大,且颗粒平均撞击角度降低。研究结果为冲缝筛管在油气田的应用安全性提供了一定参考。

In connection with the erosive problem of calking screen caused by solid particles in the fracturing flowback process,this paper analyzes the erosive behavior of particles approaching to the wall surface,providing basis for the erosive research of underground prevention sand tools.By means of Computational Fluid Dynamics(CFD),based on Dense Discrete Phase Model(DDPM),researchers compiled the user-defimed function(UDF),and studied the motion characteristics of particles about number,speed and angle when they hit the wall under the fraction of high sandy quality.Then critical erosive flow speed has been determined through the increasing rate of erosive velocity.The results show that in the process of fracturing flowback,the hitting speed of particles increase with the increase of inlet flow rate,which is the major reason to cause the increase of erosion spee1d rate.When inlet flow rate increases to 12 m/s from 6 m/s,the largest value of erosion velocity at the exit of eyelet raises to 3.42×10^(-1) mm/kg from 3.54×10^(-2) mm/kg,increasing 9.66 times;Hitting angles of particles don’t change with the increase of flow speed;The increase of sandy quality fraction results in the increase of particle numbers at the inlet exit,followed by the increase of particle hitting frequency,the reduction of particle average hitting speed,the enhancement of velocity perturbation width,meanwhile by the larger perturbation width of average hitting angles of particles,but by the lower angle of average hitting of particles.Research results provide certain references for the application safety of calking screen in the oil-gas fields.