Analysis of eccentric wear between sucker rods and oil pipes

The pumping rod continuously moves back and forth inside the oil pipe, sometimes causing severe wear of the oil pipe or the oil pipe continuously rotating or expanding with the movement of the pumping rod, resulting in severe wear of the outer wall of the oil pipe and the casing. In the process of oil development, friction is formed between the pumping rod of the beam type pumping unit and the oil pipe, as well as between the oil pipe and the reservoir casing during normal production and various special operations, which is commonly known as eccentric wear. The eccentric wear of the tubing can be divided into two types according to their ways: one is the internal wear of the sucker rod coupling and its body with the tubing, and the other is the internal wear of the tubing coupling and its body with the casing.

The phenomenon of eccentric wear is commonly found in various production wells such as vertical wells, inclined vertical wells, directional wells, and horizontal wells. It is also a factor that has a significant impact on the failure of oil pipes. Oil wells with a deviation angle greater than 5 degrees can be included in the range of deviated wells. Due to the different inclinations of the oil well during the drilling stage, the sucker rod comes into contact with the oil pipe at certain positions during the up and down movement, causing friction and collision, and varying degrees of eccentric wear. In areas with smaller curvature of the wellbore, the inner wall of the oil pipe only rubs against the coupling of the sucker rod, with a larger area and lighter eccentric wear. In areas with greater curvature, the inner wall of the oil pipe not only rubs against the coupling of the pumping rod, but also against the main body of the pumping rod, and the contact surface is small, resulting in severe eccentric wear and even causing the oil pipe to wear through and the pumping rod to break.