Numerical Simulation Of Liquid-Solid Two-Phase Flow In Annular Wellbore

Cattings deposit in the well will lead to slacking off,pump blocking,sticking,high torque,high friction pressure loss and other accidents.There are many factors affecting cuttings transportation,and the interaction between different factors is complicated.Hence it is of practical significance to study the liquid-solid two-phase flow in annulus of well.Based on Euler-Euler two-phase model,flow behavior of liquid-solid two-phase was simulated in this paper.This paper used the turbulence model to solve the flow,the Gidaspow drag model to simulate interfacial momentum transfer,the user defined function(UDF)to realize the rotation of the drill pipe,and the dynamic mesh technique of FLUENT to simulate the three-dimensional flow field of liquid-solid two-phase fluid flow in annulus.The characteristics of liquid-solid two-phase flow in annulus are theoretically analyzed by studying the influence of different factors on bringing cuttings,such as inlet liquid velocity,rod rotation speed,liquid density,liquid viscosity,particle diameter,drilling speed and fluid type(Newton fluid and power-law fluid).The results show that increasing inlet velocity,rod rotation speed,liquid viscosity and liquid density are beneficial to the cuttings transportation.However,when the inlet velocity increases to a certain value,the annular pressure drop begins to rise,and a moderate increase will contribute to the cutting rising;the rotation of the drill pipe can increase the turbulence of the annular liquid and bring the debris into the high velocity zone of annular space.Whereas when the drilling speed increases to a certain value,it has little effect on debris transportation;increasing liquid density can improve the ability of the liquid to carry cuttings in the upstream and suspend cuttings in the static;within a certain range,the greater the viscosity of the liquid,the greater the drag force between the particles,and the stronger the carrying capacity of the liquid;increasing particle diameter and drilling speed are unfavorable to the movement of cuttings;increase the consistency coefficient will increase the power-law fluid apparent viscosity,thereby increasing the drag between liquid and solid phase;increasing the flow index will also increase the apparent viscosity of the power-law fluid,and it has more influence on the turbulent kinetic energy and turbulent dissipation rate.