Dynamic response analysis of carbon fiber sucker rod column under axial motion

Abstract It has been demonstrated that steel sucker rod strings are susceptible to failure during the process of oil production. Such failure can be attributed to two primary factors: corrosion and insufficient strength. Conversely, carbon fiber sucker rods have gained a notable presence in ultra-deep wells and corrosive wells, a testament to their exceptional strength and corrosion resistance. During operation, composite sucker rods composed of carbon fiber and steel are subject to viscoelastic fluid and axial movement excitation at the suspension point, in addition to pump-end loads. This combination of factors leads to the development of highly complex deformation and stress patterns. This paper introduces the concept of the local hydraulic damping coefficient and considers axial motion, viscoelastic fluid force, and non-uniform axial load. The microelement method is employed to derive the dynamic equation of the carbon fiber combined pumping rod. The establishment of a dynamic model of the carbon fiber combined pumping rod and column is predicated on two fundamental equations: the longitudinal vibration equation of the pumping machine’s suspension point and the plunger liquid load law. The differential method was employed to solve the model and ascertain the load-change mechanism of the suspension point, the concentrated axial load at the pump end, and the axial distributed load of the combined pumping rod and column. The findings of the study indicate that altering the diameter of the sucker rod pump, the stroke times, and the stroke length of the pumping unit causes significant changes in the concentrated load at the pump end, making the sucker rod string prone to buckling. The axial load distribution along the carbon fiber composite sucker rod string fluctuates with time and rod length. Increased stroke rates result in greater axial load distribution along the rod string, thereby increasing the likelihood of uneven wear on the sucker rods.