The Research With Corrosion Resistance To Stress Of Sucker Rod In High Water Conditions

At present,most oilfields in China have entered the Medium or high water Production stage,in order to reduce the development cost, high strength sucker rod is used widely, and the fracture problem of high strength sucker rod is also more and more prominent. In this paper, In combination with the practical situation of oilfield, the research work about the high strength sucker rod resistance to stress corrosion and medium corrosion of the sucker rod was carried out combined with the actual oilfield, carried out with the high strength sucker rod resistance to stress corrosion and medium corrosion of the sucker rod, to find out the causes of strength sucker rod stress corrosion resistance ability of the poor.Firstly, analyzed the sucker rod stress and showed the relationship between the sucker rod deformation and fracture, and then analyzed the influence factors of sucker rod corrosion fatigue life.come up with the way to determine whether the resistance to stress corrosion of two suckers is good or bad by stress corrosion test and determination of the size of plastic loss and loss of strength of the ordinary sucker rod and the high strength material.Then, based on the analysis of the stress corrosion test method and the stress corrosion testing machine,and according to the existing experiment condition, a ring stress corrosion performance testing system and slow strain rate stress corrosion test system were selected and purchased, supported by the stress corrosion device, temperature control device, camera device.in that way we built the stress corrosion test platform.Based on the investigation and analysis of Oilfield water quality, we statisticed the major ions in the presence of liquid in Shengli Oilfield Well, which laid the foundation for simulate the downhole corrosion environment. On this basis, designed the L25(56) orthogonal test, resistance to high water stress corrosion sucker different conditions were tested. By processing the test results, we got that in high water conditions, the impact of resistance to stress corrosion sucker most significant factor for the sucker rod material can; that the resistance to stress corrosion high strength sucker rod pumping no better than low-intensity resistance to stress corrosion rod oil well; that pH value of the liquid oil wells, sucker rod stress levels can also have a more significant impact on the high water conditions sucker resistance to stress corrosion. According to the experiment, it is recommended in corrosive environments, 20 CrMoA sucker is priority, and followed by SSYD-1 sucker. Field practice has proved the correctness of the proposal.On the basis of tests, we come up with the concept that when using column classic bar design high strength sucker rod string, we should select a different Goodman to ordinary sucker coefficient, which is related to sucker material and oil well’s pH value.Finally, by using GB GB / T 15970.1-1995 standard and NACE TM 0177-2005, we designed the orthogonal experiment, and carried out 4330 high resistance to stress corrosion sucker rod strength evaluation test. by the standard ECSS-Q-ST-70-37 C evaluation methods, the 4330 high strength sucker rod resistance to stress corrosion were evaluated. We obtain the conclusion that 4330 high strength sucker rod has good resistance to stress corrosion, which laid the theoretical foundation of extension of the 4330 high strength sucker rod.