The difference between Conventional & Mark II Pumping Units

This article helps understand the difference between Conventional & Mark II pumping units in term of production performance. SROD, the predictive program from General Electric (GE), has been used in order to compare the Reducer Torque Performance,  the Stroke Length, and the Polished Rod Velocity, of a conventional unit and a Mark II unit. In order to do that, production data from the well MF-1 are used.

MF-1 is an oil well activated using a sucker rod pump. The target rate is 500 BPD, the pump is set at 6000 ft, the plunger diameter is 1.5 inch, the rod string is 86, the stroke length is 144 inch and the pumping speed is 13 spm.

Reducer Torque:

  • Reducer Torque vs. Crank Angle:

SROD, the predictive program from GE, has been used in order to compare the reducer torque performance of a conventional unit and a Mark II unit. The plots “Torque (in in-lbs) versus the crank angle” are depicted in the following graph.

Note that the MKII does a better job approaching the uniform torque goal than the conventional unit and therefore has lower peak torque.

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10 Types of Rod Pumping Units

1. Conventional Unit:

The conventional pumping unit is a modern version of the beam pumping unit first built in 1926 with the invention of crank counterbalance.  It is a rear mounted class 1 lever system with crank counterbalance.

Typically, if one were to drop a plumb line off the equalizer bearing that line would fall over the center of the crankshaft. This machine can be rotated both Clockwise (CW) and Counterclockwise (CCW) with approximately the same performance characteristics.

It is manufactured in a wide variety of sizes and it can be fitted with many types of prime-mover bases that attach to the normal unit base.

This is the most common pumping unit type, because of its relative simplicity of operation, low maintenance requirements and adaptability to a wide range of field applications. As the cranks on a conventional unit rotate, the pitman side members cause the walking beam to pivot on a center bearing, moving the polished rod. Adjustable counterweights are located on the cranks.

As detailed by the article titled “Beam Pumping Unit Principles and Components“, most important parts of the conventional units are: Base, Counterweight, Crank, Samson Post, Horse Head, Walking Beam, Equalizer, Pitman, Gear Reducer, Brake and Prime Mover.

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