Sucker rod

A sucker rod is a steel rod, typically measuring between 7 and 9 metres (25 and 30 ft) in length, with threaded ends at both sides. It is used in the oil industry to connect the surface components with the downhole components of a reciprocating piston pump in an oil well. The pumpjack, which is the visible above-ground drive for the well pump, is linked to the downhole pump at the base of the well through a series of interconnected sucker rods. Sucker rods are also available in fiberglass, typically manufactured in lengths of 37 1/2 feet and diameters of 3/4, 7/8, 1, and 1 1/4 inch. These rods feature metallic threaded ends, female on one side and male on the other.

The line of sucker rods is represented in this diagram by the solid black line in the center of the well

The surface unit transfers energy from the prime-mover to the sucker rod string to facilitate well pumping. It achieves this by converting the rotary motion of the prime-mover into the reciprocating motion required by the sucker rod and reducing the prime-mover's speed to a suitable pumping rate. Speed reduction is managed through a gear reducer, while the rotary motion of the crankshaft is transformed into oscillatory motion using a walking beam. The crank arm connects to the walking beam via a pitman arm. The walking beam is supported by a Samson post and saddle bearing. The horse head and bridle ensure vertical pull on the sucker rod string at all times, preventing bearing movement above the stuffing box. A combination of the polished rod and stuffing box is employed to maintain an effective liquid seal at the surface.

See also

• Oilfield terminology

References

• Schlumberger Oilfield Glossary: Sucker rod
• Welding Sucker Rod That Meets API Standard is Supplied