Pumpjack
A pumpjack is the overground drive for a reciprocating piston pump in an oil well.[1]
It is used to mechanically lift liquid out of the well if there is not enough bottom hole pressure for the liquid to flow all the way to the surface. The arrangement is often used for onshore wells. Pumpjacks are common in oil-rich areas.
Depending on the size of the pump, it generally produces 5 to 40 litres (1 to 9 imp gal; 1.5 to 10.5 US gal) of liquid at each stroke. Often this is an
A beam-type pumpjack converts the rotary motion of the motor to the vertical reciprocating motion necessary to drive the polished-rod and accompanying sucker rod and column (fluid) load. The engineering term for this type of mechanism is a walking beam. It was often employed in stationary and marine steam engine designs in the 18th and 19th centuries.
Names
A pumpjack is also called a beam pump, walking beam pump, horsehead pump, nodding donkey pump (donkey pumper), rocking horse pump, grasshopper pump, sucker rod pump, dinosaur pump, Big Texan pump, thirsty bird pump, hobby horse, or just pumping unit.[2]
Above ground
Modern pumpjacks are powered by a prime mover. This is commonly an electric motor, but
The prime mover runs a set of pulleys to the transmission, often a
The cranks themselves also produce counterbalance due to their weight, so on pumpjacks that do not carry very heavy loads, the weight of the cranks themselves may be enough to balance the well load.
Sometimes, however, crank-balanced units can become prohibitively heavy due to the need for counterweights. Lufkin Industries offer "air-balanced" units, where counterbalance is provided by a pneumatic cylinder charged with air from a compressor, eliminating the need for counterweights.
The polished rod has a close fit to the stuffing box, letting it move in and out of the tubing without fluid escaping. (The tubing is a pipe that runs to the bottom of the well through which the liquid is produced.) The bridle follows the curve of the horse head as it lowers and raises to create a vertical or nearly-vertical stroke. The polished rod is connected to a long string of rods called sucker rods, which run through the tubing to the down-hole pump, usually positioned near the bottom of the well.
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Picture of a pump jack used to mechanically lift liquid out of the well if there is not enough bottom hole pressure for the liquid to flow all the way to the surface. -
The densely developed Kern River Oil Field, California: Hundreds of pumpjacks are visible in the full-size view. This style of development was common in the oil booms of the early 20th century. -
A pumpjack in Southern Alberta fueled by natural gas.
Down-hole
At the bottom of the tubing is the down-hole pump. This pump has two ball check valves: a stationary valve at bottom called the standing valve, and a valve on the piston connected to the bottom of the sucker rods that travels up and down as the rods reciprocate, known as the traveling valve. Reservoir fluid enters from the formation into the bottom of the borehole through perforations that have been made through the casing and cement (the casing is a larger metal pipe that runs the length of the well, which has cement placed between it and the earth; the tubing, pump, and sucker rod are all inside the casing).
When the rods at the pump end are travelling up, the traveling valve is closed and the standing valve is open (due to the drop in pressure in the pump barrel). Consequently, the pump barrel fills with the fluid from the formation as the traveling piston lifts the previous contents of the barrel upwards. When the rods begin pushing down, the traveling valve opens and the standing valve closes (due to an increase in pressure in the pump barrel). The traveling valve drops through the fluid in the barrel (which had been sucked in during the upstroke). The piston then reaches the end of its stroke and begins its path upwards again, repeating the process.
Often, gas is produced through the same perforations as the oil. This can be problematic if gas enters the pump, because it can result in what is known as gas locking, where insufficient pressure builds up in the pump barrel to open the valves (due to compression of the gas) and little or nothing is pumped. To preclude this, the inlet for the pump can be placed below the perforations. As the gas-laden fluid enters the well bore through the perforations, the gas bubbles up the annulus (the space between the casing and the tubing) while the liquid moves down to the standing valve inlet. Once at the surface, the gas is collected through piping connected to the annulus.
Water well pumpjacks
Pumpjacks can also be used to drive what would now be considered old-fashioned hand-pumped water wells. The scale of the technology is frequently smaller than for an oil well, and can typically fit on top of an existing hand-pumped well head. The technology is simple, typically using a parallel-bar double-cam lift driven from a low-power electric motor, although the number of pumpjacks with stroke lengths 54 inches (1.4 m) and longer being used as water pumps is increasing. A short video recording of such a pump in action can be viewed on YouTube.[6]
Although the flow rate for a water well pumpjack is lower than that from a
See also
- Gas lift
- Progressive cavity pump
- Submersible pump
References
- ^ "Old Stuff from the Oil Fields - Pumping Jacks". www.sjvgeology.org. Retrieved 2017-03-22.
- ^ "Colorful "pumpjack," a type of small oil pump that's a common sight in West Texas, along U.S. 83 near the town of Winters in Runnels County, Texas". Library of Congress. 2014-03-07. Retrieved 2021-10-11.
- ^ "Oil History: The Central Power". Retrieved 2011-02-05.
- ^ "Single Phase Motors". Archived from the original on 2005-02-26. Retrieved 2017-04-29.
- ^ "Options Beyond Three-Phase For Serving Remote Motor Loads" (PDF). Archived from the original (PDF) on April 2, 2017. Retrieved April 29, 2017.
- YouTube
External links
- All Pumped Up – Oilfield Technology, The American Oil & Gas Historical Society, updated October 2014