A Technique For Measuring And Evaluating The Performance of a Beam Pumping System

Abstract

Because of ever-changing pumping loads, and the problem of determining what proportion of the fluid load is elevated by the artificial lift system and what part by the reservoir, beam pumping performance has, in the past, been difficult to accurately measure, interpret and understand. Often, beam pumping units are performing in an exemplary fashion, without the operator's knowledge or appreciation of the machine's economy and effectiveness. Occasionally, beam pumping units are misapplied, marginal performers, and yet the operator mistakenly believes them to be efficient and economical. Outlined below is asimple and precise technique, inexpensive and easy to follow, that accurately compares and rates a beam pumping unit's mechanical performance, as well as its economy of operation. This simple method can also be used to rate the effectiveness and economy of the unit's prime mover.

IMPORTANT

BECAUSE OF the complex behaviour of sucker rod pumping systems with their involved harmonic force patterns, it is desirable that performance comparisons between different beam pumping geometries, and/or different prime movers, be made on the basis of both (or all) systems, having approximately the same stroke length and pumping speed. It is also recommended that the same, or similar bottomhole pump and downhole conditions exist, as to pump submergence and volumetric efficiency. Unstable wells, fluid and gas pound, as well as other pumping irregularities may reduce the accuracy of comparative results.

GENERAL
.
It has been estimated that, as of 1971, the number of beam pumping units in service throughout the world exceeded the half million mark. Interestingly, a large percentage of these primitive machines employ the same basic geometry used on the earliest oilfield pumping mechanisms, over a century ago.

Despite its advanced age and substantial numbers, little attention has been given to the development of a technique for measuring or evaluating the beam pumping unit's functional ability - either comparing the performance characteristics of different types of pumping unit geometries or comparing the unit's performance to some fixed reference.

Inattention to this aspect of beam pumping technology is understandable, because, for many years, most beam-type geometries were essentially alike, obviously resulting in the same or similar performance. Additional1y, operators were engaged in oil production, so that they had little time or inclination to study the slight variations between various units.

With the advent of the air balance unit in the 1920's, pumping unit geometry took on a different look, with substantial1y altered geometric and kinematic characteristics and performance. The air balance unit was followed some years later by other types of pumping unit geometry, differing widely from that so long employed by the historic conventional unit.

For years, after the introduction of the newer types of pumping unit geometry, little thought was given to differences in performance characteristics, and it was not until H. E. Gray, a mathematician for Shell Oil Company's Research & Development Section, presented a paper entitled "Kinematics of Oil WellPumping Units" that the industry's attention was focused on the fact that pumping unit geometry and kinematics could play a significant role in the unit's functional ability, or performance.