Research and Application of Stress Calculation Method for Sucker Rod String

Abstract

Sucker rod plays a very important role in rod pumping system. If the rod string is not designed properly, it will cause sucker rod failure and affect crude oil production. Allowable stress is the key data in the design of sucker rod string. In order to accurately analyze the allowable stress of sucker rod string, one-dimensional damping wave equation and finite difference algorithm are applied in this paper to accurately analyze the maximum stress, minimum stress and maximum allowable stress of each part of sucker rod string. It is possible to pay close attention to the stress situation of sucker rod and take corresponding measures to extend the service life of sucker rod. The example shows the maximum stress value of the sucker rod is not at or near the top of the cone, for directional wells, but at the maximum inclination angle of the well section. This indicates that the well section with large inclination angle in directional wells is more likely to fail the sucker rod than the top of the cone point. Therefore, we should pay close attention to the sensitive part with large inclination angle and dogleg degree and take corresponding measures to prolong the service life of the sucker rod.