The sucker rod serves as the slender component of a pumping well, connecting the polished rod at the top to the lower portion of the sucker pump to transfer power. Typically, each sucker rod measures around 7.62 or 8 meters, with some reaching 9.14 meters. They are usually made from low-carbon alloy steel that undergoes heat treatment. These rods are joined end-to-end using internal threaded couplings and extend down into the oil layer, driving the reciprocating motion of the pump. Modern oil wells often require sucker rods extending over two kilometers in length. For instance, in Shengli Oilfield, depths exceed three thousand meters.
As a crucial element of rod-pumping equipment, the sucker rod plays a vital role in transmitting energy from the pumping unit to the downhole oil pump. The sucker rod string consists of dozens or even hundreds of rods connected via couplings. Throughout the production process, this assembly experiences asymmetric cyclic loads while operating in well fluids—often containing corrosive substances. Consequently, the primary failure modes include fatigue fractures or corrosion fatigue fractures. Breakages in the sucker rod can severely impact oil production, leading to increased maintenance costs and higher operational expenses.
Sucker rods have a rich history spanning nearly a century. Initially crafted from rattan, the first metal sucker rod patent (U.S. Patent No. 528168) was awarded to Samuel M. Jones of Ohio on October 30, 1894. Over the last two decades, significant advancements have emerged both domestically and internationally in sucker rod manufacturing. Innovations include the use of multi-element alloy steels and fiberglass, along with improvements in forging techniques like intermediate frequency induction heating and quenching devices. Advanced technologies such as infrared-guided intelligent thermometers, non-rotating sucker rod heads, automated coupling production lines, and sophisticated die designs have significantly enhanced manufacturing standards and product quality.
To address diverse operational challenges, including heavy oil wells, high-wax wells, corrosive environments, and deviated wells, numerous specialized sucker rods have been developed. Examples include ultra-high-strength sucker rods, FRP oil pumping rods, hollow sucker rods, KD-grade sucker rods, continuous sucker rods, electrically heated sucker rods, wire-rope sucker rods, and aluminum-alloy sucker rods. Additionally, various auxiliary components have been designed, such as long-stroke high-strength polished rods, toothless polished rod clamps, rotating rod devices, shock absorbers, adjustable graphite-centered polished rod seals, roller couplings, centralizers, wax scrapers, weighted rods, anti-drop devices, disconnecting mechanisms, and magnetic anti-waxing tools, all contributing to extended service life and broader applicability.
**Technical Principle:**
At the core of this innovation lies the high-strength sucker rod nipple, featuring superior tensile strength. The sucker rod coupling measures 5/8", matching or surpassing the performance of standard sucker rods. Direct contact between the oil pipe and the rod ensures optimal efficiency. Utilizing sacrificial anode electrochemical corrosion prevention, the system mitigates electrochemical corrosion caused by localized wear. By providing a cathodic current to the protected body through the electrolyte, cathodic protection is achieved. The continuous flow of current ensures the anode material is consumed steadily, effectively preventing damage due to electrochemical corrosion. To safeguard against fluid-induced erosion or collision, stainless steel sleeves encase the inner and outer wire joints and the anode body. Moreover, the coupling is constructed from high-nickel alloy, ensuring a smooth surface and significantly prolonging the lifespan of the sucker rod coupling.
**Technical Parameters:**
- Size: 1", 7/8", 3/4", 5/8"
- Supporting rod diameter: 25mm, 22mm, 19mm, 16mm
- Centralizer outer diameter: φ56mm
- Sacrificial anode potential protection range: 50m
- Effective power generation: ≥1.1 A.h/g
- Anode consumption rate: ≤12.36 kg/A.a
- Current efficiency: ≥65%
**On-Site Installation:**
During operations, the sucker rod must be properly connected and installed with the sucker rod threads. The specific installation intervals depend on the corrosion and eccentric wear conditions of the oil well, typically spaced every 80-100 meters. For optimal results, the sucker rod anti-corrosion and anti-wear device should be used alongside the KXY-2 tubing cathodic protector and common nylon centralizers.
This comprehensive approach not only enhances operational efficiency but also ensures the longevity and reliability of the sucker rod system, paving the way for more sustainable and efficient oil extraction practices.
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