连续油管的腐蚀和疲劳行为研究

发布时间：2018-05-23 20:16

  本文选题：连续油管 + Ni-W合金镀层　； 参考：《西安石油大学》2015年硕士论文

【摘要】：模拟某油田腐蚀环境,通过高温高压腐蚀试验和实物机械疲劳试验,采用金相显微镜、SEM和EDS等现代分析手段,结合QT-900连续油管“入井—空气中放置—再次入井”的实际作业过程,分析了Ni-W合金镀层对连续油管理化性能的影响,研究了H2S和CO2共存环境下连续油管在井下不同井段的腐蚀行为和CO2环境下Ni-W合金镀层对连续油管耐蚀性的影响,并探讨了在H2S环境下连续油管和Ni-W合金镀层的抗SSC性能。研究结果表明:连续油管的组织主要为珠光体和多边形铁素体。与基体连续油管材料相比,Ni-W合金镀层中Ni和W元素的含量较高,Fe元素含量较低,外壁镀层厚度平均值为54.0μm,内壁镀层厚度平均值为98.0μm,镀层与基体结合良好。Ni-W合金镀层对连续油管的拉伸性能影响不大,但是能显著提高连续油管的硬度和疲劳寿命。疲劳失效的Ni-W合金镀层油管的裂纹均起源于表面镀层,裂纹逐渐贯穿镀层,最后扩展至基体。刺口附近裂纹较为密集,距刺口350mm处裂纹较为稀疏。模拟井口(即井深0m)、1500m、3300m和4400m,对应H2S分压分别为0.020MPa、0.030MPa、0.037MPa和0.040MPa,CO2分压分别为0.97MPa、1.10MPa、1.24MPa和1.33Mpa的腐蚀环境进行不同井段腐蚀规律研究,结果表明,井下油管腐蚀是应力和环境介质综合作用的结果。一次入釜试验后,连续油管在1500m井段腐蚀最严重,局部腐蚀速率达到4.4627mm/a,腐蚀产物主要为Fe S和Fe CO3的混合物。二次入釜导致连续油管腐蚀明显加剧,试样表面腐蚀产物Fe S含量明显降低,局部腐蚀产物膜脱落严重,平均腐蚀速率达到1.5549mm/a,约为一次入釜的3倍,属于极严重腐蚀。模拟CO2分压为1.07MPa、温度为60℃、加载拉应力为439MPa的腐蚀环境研究Ni-W合金镀层的耐蚀性能,结果表明,Ni-W合金镀层显著提高了连续油管的耐CO2腐蚀性能,镀层油管的平均腐蚀速率为0.0160mm/a,约为普通连续油管的1/40,属于轻度腐蚀。在H2S应力腐蚀标准试验中,连续油管和镀Ni-W合金层油管表面均出现裂纹,未通过抗SSC性能检测。
[Abstract]:In order to simulate the corrosion environment of an oil field, by means of high temperature and high pressure corrosion test and physical mechanical fatigue test, modern analysis methods such as metallographic microscope, EDS and so on are used. The effect of Ni-W alloy coating on the physical and chemical properties of QT-900 continuous tubing was analyzed. The corrosion behavior of continuous tubing in different well sections under the co-existence of H _ 2S and CO2 and the effect of Ni-W alloy coating on the corrosion resistance of continuous tubing under CO2 environment were studied. The anti-SSC properties of continuous tubing and Ni-W alloy coating in H _ 2S environment were also discussed. The results show that the structure of continuous tubing is mainly pearlite and polygonal ferrite. Compared with the coiled tubing material, the content of Ni and W in Ni-W alloy coating is higher than that in coiled tubing material. The average thickness of outer coating is 54.0 渭 m, while the average thickness of inner coating is 98.0 渭 m. The coating has little effect on the tensile properties of coiled tubing, but it can significantly improve the hardness and fatigue life of coiled tubing. The cracks of fatigue failure Ni-W alloy coated tubing originated from the surface coating, and the cracks gradually penetrated through the coating and finally spread to the substrate. The cracks near the spines are denser than those near the 350mm. The corrosion law of different well sections in the simulated wellhead (I. e., the depth of the well is 0. 0mm / 1500mN 3300m and 4400m respectively) corresponding to the partial pressure of H _ 2S is 0.020 MPA / m ~ (0.030) MPA and 0.040 MPA / m ~ (2) CO _ 2 is 0.97 MPA / 1. 10 MPA and 1.24 MPA / 1.33Mpa respectively. The results show that the corrosion of tubing is the result of comprehensive effect of environmental medium and stress. The corrosion rate of continuous tubing was 4.4627mm / a after the first test in 1500m well, and the corrosion product was mainly the mixture of Fe S and Fe CO3. The corrosion of the coiled tubing was obviously aggravated by the secondary reactor, the content of Fe S on the surface of the sample was obviously decreased, and the local corrosion product film fell off seriously. The average corrosion rate was 1.5549 mm / a, about 3 times of that of the primary autoclave, and the corrosion was extremely serious. The corrosion resistance of Ni-W alloy coating was studied under simulated CO2 partial pressure of 1.07MPa, temperature of 60 鈩，

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