腐蚀坑对连续油管强度的影响规律研究

发布时间：2018-07-25 15:36

【摘要】：连续油管在油气作业中的应用越来越广泛,每年世界范围内连续油管用量近500万米。服役过程中承受腐蚀介质的作用,极易造成腐蚀坑等缺陷,而且承受拉伸、弯曲等复杂载荷的作用,在腐蚀坑处形成裂纹或开裂,从而导致失效。因此建立含腐蚀缺陷连续油管的强度评价方法、提出连续油管的极限腐蚀坑尺寸,是保证连续油管安全作业所急需解决的问题。本文以克深井作业的QT900钢级、Ф38.1mm×5.16mm、含腐蚀坑的连续油管作为研究对象,以API 579的相关条款为依据,采用理论分析、数值模拟的方法研究了连续油管在内压、弯曲、重力等载荷作用下的强度特征,明确了腐蚀坑对连续油管强度的影响规律,提出了极限腐蚀坑深度、剩余强度的指标,为该井区工作的含腐蚀坑连续油管的安全评价提供了理论基础和评价指标,为其他的井区工作的连续油管的安全评价提供了参考。研究结果表明:QT900连续油管作业过程中的腐蚀现象以点状腐蚀坑为主;腐蚀坑深度越大、密度越高,剩余强度越低。二级评价方法评价精度略高于1级评价方法,20MPa内压作用下极限腐蚀坑深度为4.13mm;三级评价的结果说明当连续油管受到439MPa拉伸载荷时,腐蚀坑的极限深度小于0.005mm;当连续油管的弯曲半径为1219.2mm、1257.3mm和1447.8mm时,极限腐蚀坑深度分别为0.516mm、1.032mm和1.548mm;连续油管下井过程中最危险的位置为管体经过导向架时由直变弯的过程,此过程中在439MPa拉伸载荷作用下,经过半径为1828mm的弯曲时,极限腐蚀坑深度介于0.516mm与0.774mm之间。
[Abstract]:The application of coiled tubing in oil and gas operation is more and more extensive, and the amount of coiled tubing is nearly 5 million meters in the world every year. It is easy to cause the defects such as corrosion pits and other defects in the service process by the role of corrosion medium. Moreover, the effect of complex loads, such as tensile and bending, causes cracks or cracks in the corrosion pits, which lead to failure. Therefore, it is urgent to establish the strength evaluation method of continuous tubing with corrosion defects and to put forward the limit corrosion pit size of continuous tubing to ensure the safe operation of coiled tubing. In this paper, the QT900 steel grade, 38.1mm 脳 5.16mm, corrosion pit containing continuous tubing is used as the research object. Based on the relevant articles of API 579, the internal pressure and bending of the coiled tubing are studied by theoretical analysis and numerical simulation. The characteristics of strength under the action of equal gravity load, the influence law of corrosion pit on the strength of continuous tubing is clarified, and the index of limit corrosion pit depth and residual strength is put forward. It provides a theoretical basis and evaluation index for the safety evaluation of the continuous tubing with corrosion pit working in the well area, and provides a reference for the safety evaluation of the continuous tubing working in the other well areas. The results show that the corrosion phenomenon of the 1: QT900 continuous tubing is mainly the point corrosion pit, the deeper the corrosion pit is, the higher the density is, and the lower the residual strength is. The evaluation accuracy of the second grade evaluation method is slightly higher than that of the first grade evaluation method. The ultimate corrosion pit depth is 4.13mm under the action of internal pressure of 20MPa. The result of the third grade evaluation shows that when the continuous tubing is subjected to the 439MPa tensile load, The ultimate depth of the corrosion pit is less than 0.005mm; when the bending radius of the continuous tubing is 1219.2mm / 1257.3mm and 1447.8mm, the ultimate corrosion pit depth is 0.516mm / 1.032mm and 1.548mm respectively. In this process, under the action of 439MPa tensile load, the ultimate corrosion pit depth is between 0.516mm and 0.774mm when the radius is 1828mm bending.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE983

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