TRANSVERSE VIBRATION SIMULATION OF SUCKER ROD STRINGS UNDER NORMAL DISTRIBUTED LOAD CAUSED BY VISCO-ELASTIC FLUID

When sucker rod string (SRS) undergoes an eccentric motion within the wellbore containing visco-elastic fluid for the polymer flooding pumping wells, the SRS is subjected to an alternating normal distributed load caused by visco-elastic fluid. The alternating normal distributed load caused by visco-elastic fluid is the transverse vibration excitation of the SRS. The coupling relationship between the normal distributed load caused by visco-elastic fluid and the lateral vibration displacement of SRS is considered. The mechanical and mathematical models are established for the transverse vibration simulation of SRS in tubing under the normal distributed load caused by visco-elastic fluid. The transverse vibration of the SRS in tubing is simulated through the finite difference method and Newmark method. The transverse vibration law of the SRS is analyzed due to the excitation of the initial eccentric and to the alternating normal distributed load caused by visco-elastic fluid. The simulation results show that any initial eccentricity of SRS will lead to rod tube collision in the whole well. The high frequency collision occurs in the down stroke, and the collision force takes the largest value near the bottom. Owing to the normal distributed load caused by visco-elastic fluid, the collision between rod and tubing wall is more frequent, and the eccentric wear of rod-tubing is aggravated. The transverse vibration simulation model of SRS in tubing under the normal distributed load caused by visco-elastic fluid has a direction effort on the eccentric wear analysis of rod-tubing and optimal allocation of centralizer in the polymer flooding pumping wells.