Sucker rods, pony rods, and rod couplers are important components of rod pumping systems. They transmit the power from the pumping unit on the surface to the downhole pump. The rod string is made up of several or hundreds of sucker rods connected by rod couplers. During oil production, the rod string is subjected to asymmetric cyclic loads while operating in well fluids (crude oil and formation water). Many pumping wells contain corrosive media in the well fluids. Therefore, its main failure modes are fatigue fracture and corrosive fatigue fracture. Breakage of rods can severely impact crude oil production, increase well-servicing costs, and raise crude oil operating expenses.
I. Development Status
To meet the needs of high-volume fracturing, deep well pumping with small pumps, heavy oil wells, high paraffin wells, corrosive wells, and deviated wells, many types of specialty rods have been developed domestically and abroad, such as ultra-high strength, fiberglass, hollow, continuous, electric heating, wireline, and aluminum alloy products. Many accessories for rod strings have also been studied, such as long-stroke high-strength pony rods, seal boxes for polished rod stuffing boxes, rod rotating devices, shock subs, graphite adjustable bridle load rings, rod guide tools for rod couplers, paraffin scrappers and pump-off controllers, which further improve its service life and application range.
II. Structure and Application
They are connected to rod strings via rod couplers. The upper end connects to the pumping unit via the polished rod and stuffing box, while the lower end connects to the plunger of the downhole pump. Its function is to transmit the reciprocal motion of the horse head hanger of the surface pumping unit to the downhole pump.
Its thread failures often manifest as pulled threads. However, due to the undercut design at the pin ends of modern API sucker rods that Vigor manufactured. and the use of thread rolling instead of cutting during manufacturing, such issues rarely occur nowadays.
Polished Rods have a solid, circular cross-section steel stem with upset ends. The upset ends consist of external threads, stress relief grooves, thrust face shoulders, wrench flats, upset collars, and transition radii. The external threads connect to rod couplers, while the wrench flats facilitate making up and breaking out rod joints with rod tongs.
III.Vigor's sucker rod sizes
According to the Chinese standard SY/T 5029-2005, the stem diameters of rods are 12.7mm (1/2in), 15.9mm (5/8in), 19.1mm (3/4in), 22.2mm (7/8in), 25.4mm (1in), 28.6mm (11/8in).
Sucker rods' length is usually 8,000mm or 7,620mm. To adjust the length of rod strings, there are also short rods with lengths of 410, 610, 910, 1,220, 1,830, 2,440, 3,050, and 3,660mm.
IV.What is a sucker rod used for?
API SPEC 11B "Sucker Rods" and SY/T 5029-2005 classify products into Grade C, Grade D, and Grade K. Grade C rods are used in light and medium-loaded wells. Grade D rods are used in medium and heavily loaded wells. Grade K rods are used in lightly and medium-loaded wells with corrosive fluids.
Grade C, D, and K are made of carbon steel, manganese steel, carbon steel or alloy steel, and nickel-molybdenum alloy steel, respectively. They typically go through processes like upsetting, quenching and tempering, thread rolling, shot peening, and protective coating to obtain certain fatigue and corrosion-resistant properties.
If you find yourself in need of solutions or further insights into optimizing your oil well operations, please reach out to us at info@vigorpetroleum.com. Our team is ready to assist and provide tailored solutions to meet the unique challenges of your oil and gas endeavors.
