Joint Meeting of the Rocky Mountain Petroleum Sections of AIME, 3–4 March, Denver

Abstract

By modifying the geometry of a mechanical beam type pumping unit, the age-old problem of converting rotary power to reciprocating subsurface pumping power can be accomplished at a lower and much more uniform rate. This decreased and more even rate of power that the reducer of the pumping unit requires of its prime mover, results in several marked advantages to the operator.

Introduction

As the depth of an oil well increases, certain quantities relating to mechanical or beam pumping—such as rod motion, harmonic loads, reducer loading and the power requirements of the prime mover—have become proportionately more important to the operator as well as to the piping unit manufacturer.

Of these various items, this paper will be primarily concerned with improving the torque picture that the pumping unit reducer presents to its prime mover, thereby holding the size of the prime mover to a minimum, and smoothing out and lowering the rate of its starting and operating power requirements.

To properly understand this new torsional approach, it will be helpful to review briefly the basic fundamentals of the torque relationships that exist at the crank shaft of the conventional crank counterbalanced mechanical pumping unit, and to compare them to this new system.

In the API's forthcoming History of Production Equipment, reference is made to water wells being pumped by a reciprocating piston and cylinder arrangement since the years before the birth of Christ. Certainly, a major disadvantage of this type of operation was that, on the upstroke, the total weight of both rods and fluid had to be raised, while on the down stroke, the weight of the rods alone tried unsuccessfully to put energy back into the system. This made the demands on the energy source driving the pump both intermittent and unnecessarily large.

In 1798, Cornish made a direct-acting steam pump with a cylinder directly over the well, but with a beam attached to the pump rod to which weight was applied for balancing the rod load. If this was the first example of counterbalancing a reciprocating subsurface pump, certainly several forward strides were made. This introduction of counterbalance made possible an ear—equal division I of the work load during both up and down periods. and thus, to some extent, reduced and smoothed out the power demand.

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