FACTORS AFFECTING WELL LIFE IN SUCKER-ROD PUMP OPERATION

Onshore oil fields in Azerbaijan predominantly operate with sucker-rod pumping (SRP) systems due to their proven reliability, simplicity, and cost-effectiveness in mature, low-productivity reservoirs. As most wells are in the late depletion stage, SRP remains the most suitable artificial lift method for sustaining stable production. However, the time-between-failures (TBF) of SRP-operated wells is significantly affected by various geological, mechanical, chemical, and microbiological factors, which collectively determine the operational efficiency and maintenance frequency of the wells. One of the major issues influencing SRP performance is sand production from the formation. Sand particles cause abrasive wear on pump cylinders, plungers, and valves, and may accumulate at the pump intake, reducing fill efficiency and leading to premature equipment failure. Although sand control methods such as gravel-pack completions, sand screens, and mechanical sand anchors are applied, abrasive erosion remains a common problem in unconsolidated onshore formations. Corrosion caused by high water-cut and sulfur compounds represents another critical challenge. Water accelerates electrochemical corrosion on sucker rods, tubing, and pump internals, while hydrogen sulfide (H₂S) induces sulfide stress cracking that leads to sudden structural failures. In SRP systems, which operate under continuous exposure to aggressive fluids, corrosion significantly reduces equipment lifetime and increases operational costs. Preventive measures—corrosion inhibitors, protective coatings, and periodic well cleaning—mitigate these effects but do not fully eliminate the risks. Mechanical failures of the rod string, such as loosening or breakage, have a direct impact on SRP functionality. Loosened connections reduce stroke transmission efficiency and cause unstable pump displacement, while rod breakage results in total shutdown and complicated fishing operations. These failures are typically linked to improper loading, metal fatigue, corrosion, and assembly inaccuracies. The stroke-per-minute (SPM) rate of the pumping unit also critically affects run life. Although increasing SPM can enhance oil output under favorable inflow conditions, excessive rates intensify dynamic loads, accelerate wear of rods and tubing, and reduce the pump's filling efficiency. In wells with high gas content, elevated SPM promotes gas interference, causing gas locking and irregular pump operation. Additionally, microbiologically influenced corrosion (MIC), particularly from sulfate-reducing bacteria (SRB), poses a significant risk. SRB generate hydrogen sulfide and form biofilms that create localized corrosion zones, leading to rapid pitting and weakening of metallic components. Despite the use of bactericides and corrosion-resistant materials, MIC remains difficult to fully control. Overall, the operational life of SRP systems in Azerbaijan’s onshore wells is governed by a complex interaction of abrasive, corrosive, mechanical, and biological factors. Addressing these challenges requires integrated solutions, including optimized completion design, corrosion and bacterial control programs, proper pumping parameter selection, and continuous monitoring. Enhancing TBF in SRP-operated wells directly contributes to production stability, reduced downtime, and extended economic life of mature oil fields. Keywords: artificial lift, sucker-rod pumping (SRP), corrosion and abrasion, time between failures (TBF), sand and microbial effects.