Paper: Improved Design for Slow Long Stroke Pumping Units

The theoretical efficiencies of slow, long pump strokes have been discussed for over 40 years, and at least ten companies have attempted to market some form of slow, long stroke pumping unit, being either mechanical, hydraulic, pneumatic, or a combination of these. These units have generally been unsuccessful due to rather complicated designs which often incorporated short life components or required considerably more maintenance than did beam type pumping units. Unique engineering and simplicity are the reasons for the success of this 100% mechanical slow, long stroke pumping unit. This unit will allow the operator to move a downhole pump through a slow, long stroke of 24 feet, resulting in better pump fillage, less fluid pounding, and more effective high volume or deep well production where rod stretch inefficiencies have formerly been greatly multiplied. By reducing rod stretch and requiring fewer pump cycles per barrel, this unit reduces downhole wear on pumps, sucker rods, and tubing, thus reducing downtime and increases life span of individual components. This slow, long stroke pumping unit features short torque arm drive element, hence smaller gear reducer, fewer reversals, near constant polished rod velocity, shock absorbing load belt, and direct counterweight connection. The unit's unique design avoids inefficient power demand peaks and allows the use of smaller prime movers. Results of studies comparing NEMA D motors in conventional units and slow, long stroke units will be shown. Studies comparing NEMA D and NEMA B motors operating a slow, long stroke unit are also included. This paper will discuss how higher surface equipment efficiencies and higher overall pumping efficiencies are obtained from this slow, long stroke pumping unit. This unique pumping unit extends the limits of sucker rod pumping to volumes and depths previously not possible with traditional sucker rod pumping.