| Mechanical oil extraction is the main traditional manner of oil extraction throughout the world. Pumping with rod is the most extensively used technique as well as the primary hoisting method. A new type of petroleum equipment, the flexible continuous sucker rod, highly appraised by the oil experts, has a very good application prospect because it can fully exhibit its unique excellence on machine oil extraction. So it is very useful for developing our country's petroleum industry on land.In view of the particularity of working condition and the complexity of the corrosion environment in oil welis, there are very serious corrosion and wear problems. And Nylon coating tends to craze in low temperature. These shortcomings severely impede its industrialization. Aiming at these problems, a large number of experimentation research on the surface protection materials of the flexible continuous sucker rod were made in this paper. The main achievements and innovations are as follows:1. Considering the fact that the surface protection of the continuous sucker rod behaves badly and the interconnection tends to split in low temperature, we conducted experiments of basic properties and trial-use on the nylon used as the surface protection for continuous sucker rod in tensile strength, impact strength, MI, etc. The results showed that, in terms of mechanical properties, nylon (including PA6, PA66) could basically meet the needs for application of continuous sucker rod.2. The corrosion model was established. The analysis was done for the corrosion tests, water-absorption tests as well as anti-chemicals tests. It proved that PA6-2, PA66-1 were strong in anti-corrosion. And we analyzed the synergy of various thermo-antioxidant stabilizers upon plastics and settled one antioxidant stabilizer.3. The methods and principles of the enhancement of compatibility and the modification tests of co-miscibility with PE, PP, ABS and POE were extensively done on the Nylon for the surface protection of continuous sucker rod. And we came to the conclusion that PA/ABS-g-MAH and PA/POE possessed good impact endurance and ductility in low temperature. And we established two formulas for surface protection of continuous sucker rod: (1) PA6+ABS-g-MAH+M-g-MAH+antioxidant+auxiliary; (2) PA6+POE+co-miscible agent+ antioxidant+ auxiliary.4. Friction and wear properties of the nylon coating, prepared by hot- extrusion, used to protect the surface of the flexible continuous sucker rod were studied by using a pin-on-disc wear tester in the simulated oil well environment. The effects of sliding speed and load were considered. The wear mechanism was also studied by using scanning electron microscope (SEM). The result was: (a) the friction coefficients of both kinds of materials, JKPA and ZZ7024B used to protect the surface of the flexible continuous sucker rod decreased with sliding speed increasing, but changed little withload increasing in the simulated oil well environment. The value of friction coefficient of ZZ7024B was smaller than that of JKPA. The minimum value of friction coefficient of ZZ7024B was about 0.05. (b) The wear volume of ZZ7024B was smaller than that of JKPA with the sliding speed and load increasing under the same conditions of experimentation; (c) The wear mechanisms of the two materials were different. The main mechanism of ZZ7024B was fatigue peeling and adhesive wear, but JKPA abrasive wear and adhesive wear. On the whole, the ZZ7024B exhibited very good wear resistance.5. The product line of the hot-extrusion Nylon coating for the flexible continuous sucker rod was designed. The technique of hot-extrusion for the whole rod and the technique of local hot spraying were adopted. And the techniques were feasible and in a position to meet production requirements.
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