Numerical Simulation For Flow In Eccentric Annulus With Planetary Motion Of The Inner Rod

Flow in eccentric annulus with planetary motion of the inner rod refers to that under the axial pressure gradient, fluid flow through eccentric annulus in which the inner rod rotates around its own axis while revolving around the axis of the outer cylinder. Planetary motion of the inner rod is the general situation of rod’s rotating in working condition of screw pump wells and drilling of deviated well. Rotation state of sucker rod in screw pump wells influence flow resistance of produced fluid and moment of rod significantly. Eccentric revolution of drill pipe affects inhibition of rock debris bed and drilling fluid’s ability of carrying rock debris. Since the study for such flows has engineering significance.Based on computational fluid dynamics, aiming at forms and rules for the movement of the inner rod, the UDF program that implement its planetary motion was compiled successfully. Control of speed, direction and eccentricity of rotation and revolution of the inner rod was achieved. With the application of FLUENT dynamic mesh, simulation for flow field with the inner rod’s planetary motion in annulus was achieved.Revolution trend of inner rod caused by fluid force when inner rod rotates only was calculated. Results show that: when the inner rod bears fluid force in the transverse direction only, the direction of revolution will be the same with rotation. Influence on flow field by revolution and its direction when inner rod rotate and revolute simultaneously was calculated. Results show revolution of inner rod will cause core area of axial velocity rotate around the axis of inner rod in the opposite direction of revolution and secondary flow appears when direction of revolution and rotation are opposite.For working condition of screw well, effects on fluid transport capability, secondary flow, the axial pressure drop and torque of rod by fluid power law characteristics, rotation speed, revolution speed and the eccentricity of the inner rod was calculated. The results show: with the increase of the rotation speed of the inner rod, the axial pressure drop of the fluid reduces and torque of the post increases. With increase of the revolution speed, axial pressure drop increases and the secondary flow area expands. With the increase of the eccentricity of the rod, axial velocity of fluid increases, pressure drop decreases and the torque of post increases.For working conditions of horizontal well drilling, Euler two-fluid model was used to achieving the liquid-solid two-phase flow simulation of fluid carrying rock in annulus with drill’s planetary. Effects on properties of fluid carrying rock by particle diameter, eccentricity of rod, speed and direction of the drill were calculated. The results show: cuttings bed forms easily in low-side location of wellbore annulus and revolution of drill pipe improve the effects of fluid carrying rock. With the increase of the rotation speed and the eccentricity of drill pipe, the bed rotates and more debris particles swirl with the drilling fluid. Efficiency of carrying rock by fluid improves.