A number of years ago, my company realized that existing equipment considered adequate for producing oil wells at the time would not be capable of producing wells of the future. All forecasts indicated there would be a need for equipment to produce from deeper wells and produce higher volumes from the more shallow wells.

A research and development project was initiated with the assignment of determining the most efficient means of lifting fluid from the producing zone to the stock tanks. All known producing zone to the stock tanks. All known methods of lift were investigated. The results of the investigation showed each system under a certain set of conditions could be classified as the most economical, but not necessarily the most efficient. The department finally philosophized that the most efficient means philosophized that the most efficient means would eventually develop into the most economical.

One system stood out above all others in its ability to lift fluid with the least lost effort. This, as you would suspect, was the conventional sucker-rod lift system. Further study showed that, even though the sucker-rod system over-all was the most efficient, as the loads increased either by volumes lifted or by increase in depth or a combination of the two, the efficiency of the system became much less and the projected cost of operation became too expensive to be commercially feasible.

With volumes of data on hand regarding attempted production of heavy loads utilizing sucker rods, there was one method which was able to produce fluid with a much reduced down-hole cost and a comparative good down-hole efficiency. This was the long-stroke hydraulic pumping unit.

The use of hydraulic pumping units reached its peak during the early 1950's. Without a doubt the manufacturers and the operators did everything possible to make the hydraulic unit operational, but it was a very complex piece of equipment and, except for an isolated instance or two, all the thousands of units had to be retired. The cost of maintenance was too high and the reliability far too low to be considered as acceptable.

Much was learned during this period. Due to the long stroke, at a constant velocity more fluid could be produced with far fewer cycles; hence, much more fluid could be produced by the sucker rods during their life expectancy. Subsurface pump problems were dramatically decreased. This is easily understood when you consider the barrel wear is distributed over a much greater area, and the velocity of the fluid through the valves is much lower than would be encountered with conventional surface equipment.

The research and development department then concentrated its efforts on a machine that could generate a long-stroke alternative to a beam type, which is relatively efficient at lifting lighter loads but becomes progressively less efficient as the loads increase.

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