【作者】 赵启成；

【导师】 王振清；

【作者基本信息】 哈尔滨工程大学 ， 固体力学， 2005， 博士

【摘要】 油管失效问题是石油生产中普遍存在并一直困扰石油工业大问题,随着油田的逐步开采,抽油机井油管失效事故日益频繁,给油田造成巨大的经济损失。油管失效实质是油管螺纹的失效。目前,国内外对油管螺纹的失效还未深入地进行研究。为此,本文针对大庆油田抽油机井油管螺纹失效进行了系统地实验研究和理论分析。 研制了一套油管载荷测试装置,用于测量油管在实际工况下所受拉伸力、转矩、弯矩等载荷。通过大量的油管载荷测试分析,掌握了油管工作载荷情况,在此基础上,建立油管工作时极限载荷与振动情况的理论模型。本论文还对油管受弯原因进行了分析。研究了油管螺纹的几何尺寸、形貌变化及其工作性能。 对油管螺纹在单项载荷和循环载荷作用下,分别进行了弹塑性接触有限元分析,给出油管螺纹在循环载荷作用下所表现出的力学特性,特别是应力应变集中部位(第一啮合齿齿根)的应力应变循环规律以及应力应变幅,确定了油管螺纹的卸载规律是按弹性卸载,说明了油管螺纹的疲劳类型属于高周疲劳。设计了一套动态测试系统,通过模拟现场油管工作载荷,测得油管螺纹内壁在各种载荷下的应变变化规律。并将实测结果与有限元计算结果进行对比,验证有限元的计算结果是可靠的。 通过对专业生产厂家生产的油管和现场失效的油管进行化学成份分析和机械性能测试,认为大庆油田在役油管的材质基本符合API规范,排除油管材质质量是引起油管非正常疲劳断裂失效的主要原因。 通过对油管断口的深入观察与分析,结合油管螺纹根部的应力状态,对油管疲劳裂纹的形成和扩展的机理进行了探讨。运用疲劳强度及寿命方面的描述和分析方法,对油管危险截面的螺纹根部的实际疲劳强度进行估算,指出正常使用的油管应该具有“无限寿命”。对油管断口的裂纹源区和更多还原

【Abstract】 In recent years, the tubing broken accidents of pumping wells in Daqing Oilfields have been taken place with increasing frequency, which has caused enormous economic loss to the oil fields. And the essence of the tubing failure accidents is the failure of the tubing thread. So far, the study on the tubing broken has not been carried out in depth at home and abroad. Therefore, in this paper, experimental study and theoretical analysis are made systematically on the tubing failure in Daqing Oilfields.A set of sensor used for tubing load testing was designed. The sensor can be used to measure not only tensile load, but also torsion load and bend load. Loading status of tubing in oilfields was mastered by doing lots of tubing load tests and analyses. And then the theoretical model about the limit load and the vibration of tubing has been constructed. This paper also analyzes the reasons why tubing bears bent load. As well as the geometric dimension, the shape change and the working capability of the tubing threads have been studied.The mechanical characteristics what the tubing connections subjected to the cycle tension load exhibit are gained in the third section, so are the cycle laws and the amplitude of stress and stain. The uninstall laws of the tubing connections which are also described in this section are that the tubing connections are uninstalled in linear elastic manner, in other words, the fatigue type of tubing connections belongs to the high-cycle fatigue. A set of dynamic testing signal system was designed so as to find out the strain-changing rule under different loads on inner wall of the tubing thread by simulating tubing on-site working load. The real-time and dynamic strain signal can be caught. The signals caught are stable and credible. The correctness of Finite Element calculating method and the reliability of experimental testing results were verified by contrasting the results of experimental testing with Finite Element Calculation.By means of the chemical composition analysis, the mechanical test of the tubing produced by specialized factory and fractured in oil field, we conclude that the material quality of the tubing used in Daqing has some defects, but itaccords with the API standard basically, in other words, the improper fatigue break of tubing is not mainly caused by the material quality defects.Through observing and analyzing on tubing’s fractured surface, combining with stress analyzing for tubing thread root, the mechanism of the origin and extension of tubing fatigue crack is discussed. The actual fatigue strength at the root of thread dangerous section is estimated by applying description and analyzing methods on fatigue strength and life-span. The view that normal used tubing should possess ’undated life’ is realized. The observation and energy spectrum analysis to the corrosion on the origin and extension area of tubing crack is made. It is concluded that corrosion cannot cause fatigue crack directly.The main reasons for improper fatigue fracture of tubing are found, that is, screwing and unscrewing with heavy torque for many times makes thread root of dangerous section be with high stress level, which results in the rapid decreasing of anti-fatigue strength, so as to produce congenital source of fatigue crack, and bring on abnormal fracture of the tubing. So the key measure for preventing tubing failure is to control the tightening torque. The developed ’Torque-Pump Pressure’ monitor system in this dissertation is very effective for controlling the magnitude of tightening torque.更多还原