Preventing stress related failures is an essential part of optimizing your sucker rod pumped well. Tracking the maximum and minimum rod stress along with appropriate pump off control can ensure longer life for the rods and the entire sucker-rod pumping system.

Traditionally, stress is only computed at the top of each taper. However, when stress failures occur, they happen in areas of high friction and stress which might not necessarily be near the top of the taper and therefore undetectable through traditional stress computations.

The Modified Everitt-Jennings algorithm uses finite differences to solve the wave equation. As part of the algorithm, an iteration on damping, a fluid load line calculation and a pump fillage calculation ensure that the downhole data is as accurate as possible.

One of the many advantages of using finite differences is the ability to pick finite difference nodes down the rod string.

As part of the Modified Everitt-Jennings algorithm, position, load and stress can be computed at any point in the rod string. This provides for an in-depth, step by step, stress analysis for each taper of the rod string.

In this paper, stress results from the Modified Everitt-Jennings algorithm are compared to traditional stress calculations using measured field data.

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