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.
2. Mark II Unit (MK II):
The Mark II unit has been in use for over 50 years and is manufactured in a wide variety of sizes. It is a front mounted, class III lever system with phased crank counterbalance.
The Mark II unit has an equalizer bearing between the Samson post and the well load. The equalizer bearing is located ahead or to the well side of the centerline of the slow-speed shaft.
The equalizer bearing location results in an upstroke of approximately 195° and a downstroke of 165°. This makes a slower upstroke with 20% less acceleration, which results in reduced peak polished-rod load.
This pumping unit must turn in a C’CW rotation only.
3. Reverse Mark Pumping Unit (RM):
The Reverse Mark unit geometry was first built by a company named Cabot in 1961.
The RM unit applies some of the good features of the Mark II to the conventional geometry. It has an off-set reducer that creates an up stroke of 196 degrees of crank rotation and has phased counterbalance.
The RM unit usually reduces the required torque from that required by a conventional unit to do the same job.
This pumping unit must turn in a CW rotation only.
4. Air Balanced Pumping Unit:
The air-balanced unit is a rear mounted class III lever system with air counter balance machine first built by Lufkin in early 1950’s. This machine uses the pitman to both push the walking beam up and pull the beam down to make a pumping cycle.
The air-balanced unit uses an air tank fitted with an opened ended cylinder and piston to counterbalance the pumping unit. On the down stroke, air in the tank is further compressed thus storing energy in the compressed air. Then on the up stroke the stored air energy is used to help lift part of the rod and fluid load.
The piston uses piston rings to seal a pool of oil on top of the piston. The pool of oil, in turn, seals the air from escaping from the tank and lubricates the piston/cylinder interface.
5. Low Profile Pumping Unit:
This type of unit is used where the environmental (visual) impact is an issue or for space reasons. The design’s primary feature is the short distance from the bottom of the base to the topmost part of the machine.
It is developed to provide a limited vertical dimension needed in areas with traveling irrigation systems or in urban areas.
Some units used a walking head instead of a walking beam. It is a unidirectional pumping unit producing a longer upstroke and downstroke.
6. Beam Balanced Unit:
The Beam Balanced unit has the same rugged dependability as the Conventional unit. These units fill the need of economically producing many of the shallow wells. It is used for low production – shallow wells and especially in mature oilfields. It has a very simple construction and maintenance.
7. Hydraulic Pumping Unit:
The main components of the reciprocating pumping hydraulic units are: cylinder, mast, hydraulic power unit and the special wellhead.
There are several models available in the market to fit well requirements. The hydraulic control system has been improved with the used of programmable controllers. Data transmission allows remote control, monitoring, and optimization.
The benefits of long and ultra-long stroke pumping units include:
- Increased production rates
- Reduced bottom hole equipment wear
- Decreased rod string fatigue
- Minimized tubing wear in both vertical and directional wells
- Lower occurrences of bottom hole pump gas locking
8. Long Stroke Belt Driven Unit:
Long pump stroke (up to 366 in., or 9.3 m) and virtually no minimum speed provide more complete pump fillage and lower dynamic loading. Dynamometer cards run on these applications are similar to a theoretically perfect card.
Pumping with the long stroke belt driven unit reduces stress on equipment because the rod string is operated at relatively constant velocities. Constant velocity and fewer strokes per barrel increase the run life of the pumping unit, downhole pump, and rod string. Furthermore, longer downhole stroke provides better pump compression ratio to help eliminate gas-lock problems.
Long-life, heavy-duty load belt, used to link the powertrain to the rod string, acts as a shock absorber, effectively reducing stress on the entire system. Also, the short radius of the torque arm markedly reduces required torque demand and allows the use of a smaller prime mover and gear reducer, which are less expensive to buy and operate.
The unit is shipped in one piece for ease of service and installation. Servicing a well with this type of unit is safe and simple. After the bridle and carrier bar are disconnected from the polished rod, the unit rolls away from the wellhead without any disassembly. After a workover is completed, the unit is rolled back into place, and the carrier bar is reconnected to the polished rod.
9. Hydraulic – Cable Driven Unit:
In many applications, the installation and operational benefits of this type of hydraulic unit over a traditional rod pump lead to significant savings. This unit can be installed and operate in less than 3 hours with minimal equipment and labor.
Manufacturers: Dyna Pump and Corlift.
10. Linear Rod Pumping Unit:
The Linear Rod Pump is a compact, reliable stroking unit that is capable of lifting loads equivalent to a beam pumping system of the same design HP.
The Linear Rod pump offers complete control over important surface and downhole rod pumping conditions. This allows the end user to operate the system at maximum efficiency which in turn can reduce input electrical costs.
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