介质的腐蚀性对油井管材料腐蚀疲劳性能影响研究

发布时间：2018-10-04 18:41

【摘要】：油井管在服役中不仅受到介质的腐蚀损伤,还要承受环空外压、内压、弯曲、振动等交变载荷造成的破坏,腐蚀与疲劳相互促进使油井管萌生裂纹并不断扩展,直至断裂。在腐蚀疲劳过程中,裂纹萌生寿命占总寿命的10%,裂纹扩展占总寿命的90%,其寿命主要受裂纹扩展规律控制,所以研究含腐蚀环境下裂纹扩展速率及特性,就可以较准确的预测油井管使用寿命。从而能够确保油井管在油田开发中的安全使用。通过改变介质浓度,研究13Cr油管在不同pH值、不同氯离子浓度介质的腐蚀速率。并在相应介质中研究其腐蚀疲劳裂纹扩展性能,通过腐蚀疲劳实验得出疲劳裂纹扩展曲线,结合腐蚀速率探究不同腐蚀介质对油井管材料腐蚀疲劳性能影响规律,并得到以下结论:(1)油井管材料13Cr耐腐蚀性较好,但腐蚀速率依然会随着氯离子浓度的升高而加快,氯离子浓度对腐蚀疲劳裂纹扩展速率影响不是很大,一是氯离子浓度梯度取的不够大,二是氯离子浓度对腐蚀疲劳裂纹扩展的影响较小。(2)油管材料13Cr在不同pH值的氯化钠溶液中具有较好的耐腐蚀性,但也会随着pH值的降低腐蚀速率加快。而在腐蚀疲劳中,裂纹扩展速率却会随着酸性的增强而降低,说明13Cr材料抗腐蚀性并不代表其抗腐蚀疲劳性能。(3)相比大气环境,腐蚀性介质中疲劳裂纹扩展速率更快;在裂纹扩展后期CO2会加速疲劳裂纹扩展;不同材料在相近腐蚀介质中疲劳裂纹扩展速率差异明显。
[Abstract]:Oil well pipe is not only damaged by medium in service, but also damaged by cyclic pressure, internal pressure, bending, vibration and so on. Corrosion and fatigue promote oil well pipe to crack and expand until fracture. In the process of corrosion fatigue, crack initiation life accounts for 10% of total life, crack propagation accounts for 90% of total life, and its life is mainly controlled by crack growth law. The service life of oil well pipe can be predicted more accurately. Thus it can ensure the safe use of oil well pipe in oilfield development. The corrosion rate of 13Cr tubing in different pH values and different chlorine ion concentrations was studied by changing the concentration of the medium. The corrosion fatigue crack propagation performance was studied in the corresponding medium. The fatigue crack growth curve was obtained by corrosion fatigue test. The influence of different corrosion medium on corrosion fatigue performance of oil well pipe material was studied in combination with corrosion rate. The conclusions are as follows: (1) the corrosion resistance of 13Cr is good, but the corrosion rate will be accelerated with the increase of chloride concentration, and the effect of chloride concentration on corrosion fatigue crack propagation rate is not great. One is that the gradient of chloride concentration is not large enough, the other is that chlorine ion concentration has little effect on corrosion fatigue crack propagation. (2) tubing material 13Cr has better corrosion resistance in NaCl solution with different pH value. However, the corrosion rate will be accelerated with the decrease of pH value. However, in corrosion fatigue, the crack growth rate decreases with the increase of acidity, which indicates that the corrosion resistance of 13Cr does not represent its corrosion fatigue performance. (3) compared with the atmospheric environment, the fatigue crack growth rate in corrosive media is faster; At the later stage of crack growth, CO2 accelerates the fatigue crack growth, and the fatigue crack growth rate of different materials in the same corrosion medium is obviously different.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TE983

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