φ139.7 mm×10.54 mm G105钻杆刺穿失效分析

采用宏观分析、化学成分分析、力学性能试验、金相检验、扫描电镜断口分析及能谱分析等手段对某规格为φ139.7 mm×10.54 mm的G105钻杆的刺穿原因进行了分析。结果表明:钻杆刺穿的实质是早期疲劳失效;蹩钻、跳钻等钻柱振动引起钻杆上产生的严重交变应力是导致钻杆失效的主要原因;钻井液中的溶解氧对钻杆外表面造成氧腐蚀并形成腐蚀坑,促进了疲劳裂纹的萌生;钻铤直接过渡到钻杆,截面变化突然,使应力集中加剧,也是导致钻杆发生疲劳失效的原因之一。建议在钻井液中添加除氧剂和缓蚀剂,并适当降低钻压,调整钻井参数,避免钻柱剧烈振动。     

S135钻杆刺漏失效分析及疲劳验证试验

某井在勘探开发过程中,发生多起S135钻杆刺漏失效,对失效钻杆材料进行了化学成分、显微组织、力学性能等一系列理化检验,并对裂纹扩展面进行了详细的微观分析,获得了钻杆的失效模式为腐蚀疲劳失效。针对失效模式,对钻杆材料进行了圆棒小试样的拉压疲劳试验,获得了失效钻杆材料在高应力下的疲劳寿命,佐证了钻杆设计中设计系数的科学性,为钻杆失效原因判定提供了试验数据支持。分析结果表明:钻杆失效的主要原因是钻杆外表面发生氧腐蚀形成腐蚀坑,腐蚀坑底应力集中导致的局部高应力促使了疲劳裂纹的萌生,当裂纹扩展穿透整个壁厚后便形成刺漏失效。     

φ127mmS135钻杆刺漏失效分析

采用宏观分析、化学成分分析、金相检验、断口分析和力学性能检测等方法并结合钻杆的受力和环境工况对φ127mmS135钻杆管体发生刺漏失效的原因进行了分析。结果表明：钻杆的刺漏失效形式为腐蚀疲劳失效;钻杆外表面存在腐蚀坑,在交变应力的恶劣工况作用下于腐蚀坑底部萌生疲劳裂纹并扩展,最终发生刺漏失效。     

S135钻杆刺漏失效分析

通过宏观检验、化学成分分析、金相检验：和力学性能测试等方法,结合钻杆的受力和环境工况,对S135钻杆管体刺漏失效原因进行了分析。结果表明：刺漏失效是由于失效钻杆位于钻柱“中和点”区域,其外表面具有应力集中的腐蚀坑在交变应力和弯曲应力等共同作用下,在坑底萌生疲劳裂纹并扩展所致。     

钻杆接头台肩根部刺漏失效分析

通过力学性能测试、化学成分分析、金相检验和断口分析等方法对某井发生的钻杆接头台肩根部刺漏失效原因进行了分析。结果表明：材料冲击功低于标准要求,接头台肩根部受到严重腐蚀,形成大而深的腐蚀坑,在交变应力作用下,裂纹萌生于腐蚀坑底部,并迅速扩展,最终导致钻杆接头发生早期腐蚀疲劳失效。     

S135钻杆失效分析

采用扫描电镜、电子探针以及光谱仪等手段对某油田S135钻杆的刺穿失效进行了分析.结果表明,因氯离子在钻杆表面形成点蚀,在应力作用下引发腐蚀疲劳开裂形成刺穿造成钻杆失效,提出了相关预防措施.     

G105钢级钻杆刺漏原因分析

某油井先后出现多起G105钢级钻杆刺漏事故,采用宏观观察、化学成分分析、金相检验、力学性能试验、微观分析、涂层质量评价、能谱分析等方法对钻杆的刺漏原因进行了分析,并对钻杆加厚过渡带的应力分布进行了有限元模拟分析。结果表明:钻杆的内涂层在井内腐蚀介质的长期影响下起泡脱落,钻杆内壁基体被腐蚀,在造斜井段交变载荷作用下于钻杆应力集中的加厚过渡带的腐蚀坑处产生疲劳裂纹,裂纹扩展最终导致钻杆刺漏。     

某油田用油管断裂失效分析

某油田直井气井在正常产气56d(天)后发生油管本体断裂失效。通过宏观检验、化学成分分析、力学性能测试、金相检验、扫描电镜及能谱分析,对该油管的失效原因进行了综合分析。结果表明:该油管的断裂性质属于腐蚀疲劳断裂;外表面脱碳降低了油管的耐腐蚀能力,在服役过程中管材外表面接触水及空气的位置发生氧腐蚀,形成腐蚀坑,腐蚀坑底部产生应力集中成为疲劳裂纹源;在外力作用下疲劳裂纹不断扩展,最终导致了油管的断裂失效。     

110钢级φ88.9mm×6.45mm超级13Cr钢油管刺穿失效分析

采用宏观分析、化学成分分析、力学性能测试、金相检验及扫描电镜断口分析等手段,对某油田一根规格为φ88.9mm×6.45mm的110钢级超级13Cr马氏体不锈钢油管的刺穿失效原因进行了分析。结果表明:油管失效的实质是油管发生了氯离子应力腐蚀开裂,裂纹起源于外壁腐蚀坑底部,从外壁向内壁扩展,直到穿透壁厚,形成刺穿通道,高压流体从内向外刺出并在随后的过程中形成了刺穿孔洞。     

列车用弹簧断裂原因分析

采用直读光谱仪、光学显微镜和扫描电子显微镜等分析手段对断裂弹簧进行了失效分析。结果表明,该弹簧断裂性质为腐蚀疲劳断裂。弹簧表面与表面的有机涂层存在一定的间隙,外界的水蒸气和腐蚀性离子会穿透有机涂层,对基体材料造成腐蚀,产生腐蚀坑,形成应力集中点,在交变载荷和腐蚀性介质的共同作用下产生裂纹源,最终发生腐蚀疲劳断裂。     

Failure analysis of IEU drill pipe wash out

Many 127.0×9.19 mm IEU G105 drill pipe failures of wash out occurred after 2367 h of pure drilling time and 8726 m of penetration footage. This paper gives a detailed investigation on these failures and a systematic analysis is carried out on service and loading conditions of the drill pipes. Measurement and inspection were performed on configuration dimensions, chemical composition, mechanical performance, metallography, macro-fractography, micro-fractography, and corrosion products. Configuration stresses at the crack positions of the drill pipe were calculated by FEA. Crack extending velocity of the drill pipe material under corrosion medium was also measured. It is thought from test and analysis results that the drill pipe wash out or fracture accidents were premature corrosion fatigue failure accident. The failure courses were as the following: corrosion pits occurred first on the internal surface at the stress concentrating area of the drill pipe, and then fatigue cracks initiated in pit bottoms, and washed out or fractured subsequently as cracks penetrated through the wall thickness of the drill pipe. The reasons of drill pipe wash out were related to configuration, material quality, and load condition of the drill pipe string.     

A study of fatigue crack growth from artificial corrosion pits at welded joints under complex stress fields

The paper studies the effects of artificial corrosion pits and complex stress fields on the fatigue crack growth of full penetration load‐carrying fillet cruciform welded joints with 45° inclined angle. Parameters of fatigue crack growth rate of welded joints are obtained from S‐N curves under different levels of corrosion. A numerical method is used to simulate fatigue crack growth using different mixed mode fatigue crack growth criteria. Using polynomial regression, the crack shape correction factor of welded joints is fitted as a function of crack depth ratios. Because the maximum circumferential stress criterion is simple and easy to use in practice, fatigue crack growth rate is modified using this criterion. The relationship of effective stress intensity factor, crack growth angle and crack depth is studied under different corrosion levels. The simulated crack growth path obtained from the numerical method is compared with the actual crack growth path observed by fatigue tests. The results show that fatigue cracks do not initiate at the edge or bottom of pits but at the weld toes where the maximum stress occurs. The artificial corrosion pits have little effect on the effective stress intensity factor ranges and crack growth angle. The fatigue crack growth rates of welded joints with pits 1 and 2 are 1.15 times and 1.40 times larger than that of the welded joint with no pit, respectively. The simulated crack growth path agrees well with the actual one. The fatigue life prediction accuracy using the modified formulation is improved by about 18%. The crack shape correction factor obtained using the maximum circumferential stress criterion is recommended being used to calculate fatigue life.     

DZ55钢级Ф102mm×9.19mm地质钻杆管体断裂原因分析

通过宏观分析、金相检验、化学成分分析、力学性能测试和扫描电镜微观分析对一DZ55钢级Ф102mm×9.19mm地质钻杆的断裂原因进行了分析。结果表明：因该地质钻杆管体外壁存在较多的螺旋状划痕和刮蹭痕迹造成应力集中,加之钻杆材料韧性较低,从而导致钻杆管体在钻进过程中于损伤处萌生裂纹,裂纹不断扩展最终发生脆性断裂。     

A study on axial cracking failure of drill pipe body

Frequently happening drill pipe failure accidents in oil and gas wells not only affect drilling speed, but cause enormous economic losses and many safety issues. Most of these accidents are transverse cracking of drill pipe body and pin thread or axial cracking of box thread. Based on the axial cracking failures of drill pipe body in an ultra-deep well in China, this paper give a systematic analysis of axial cracking failure in consideration of service condition, material quality and stress corrosion mechanism. Measurement and inspection are performed on macroscopic and microscopic morphology of crack surface, corrosion products and circumferential residual stress. Then stress corrosion cracking experiments against hydrogen sulfide is conducted. Finally, the critical stress value for sulfide stress corrosion cracking of the drill pipe material is obtained, and the mechanisms of axial cracking failure and corresponding preventive measures are proposed.     

Fatigue behavior of surface cracked filament wound pipes with high tangential strength in corrosive environment

The aim of this study is to examine the corrosion fatigue behavior of filament wound composite pipes with a surface crack under alternating internal pressure. The filament wound pipes are composed of multi-layered E-glass/epoxy composites with a [±75°]₃ lay-up. The surface notches were formed on the outer surface of the pipe along the pipe axis. Dilute (0.6 M) HCl acid was applied to the surface crack region by a corrosion cell mounted on the outer surface of the pipe. The results of an experimental investigation into the corrosion fatigue tests are conducted to observe the oil leakage failure and the crack propagation of the composite pipe subjected internal pressure loading with an open ended condition in which the pipe can be deformed freely in the axial direction. The internal pressure was generated by conventional hydraulic oil for fatigue loading. The fatigue tests are performed at 0.42 Hz frequency and a stress ratio of R = 0.05 in accordance with ASTM D-2992 standard. The oil leakage from the crack tip was observed after the crack propagation reached to the critical stress intensity level. The fatigue crack propagation behavior with the environment exposure was strongly dependent on the crack parameters such as crack-depth ratio and crack-aspect ratio. The micro structure of the fracture surface with the effect of environment and the fatigue loading were also observed.     

Corrosion fatigue behavior of a heat-treated carbon steel and its statistical characteristics

The investigation of fatigue damage in corrosive environments is an important problem, because such environments reduce fatigue strength far below the typical fatigue strength determined in air. In this study, rotating bending fatigue tests of plain specimens in NaCl solution were carried out using a heat-treated 0.45% carbon steel, in order to clarify the physical background of corrosion fatigue damage. The emphasis is to perform the successive observations by the plastic replica method. The results show that corrosion pits are generated at the early stages of cycling, then most of them grow with further cycling until a crack is initiated from each corrosion pit. The initiation of corrosion pits from slip bands is only observed in the case when the stress range is relatively large, in the range of stress under which slip bands are produced in air. After initiation of a crack, a crack propogates by accompanying frequent interaction and coalescence with other cracks. The growth rate of an especially small crack in NaCl solution is larger than that in air. However, the growth rate of a comparatively large crack is smaller in NaCl solution than in air. Moreover, the statistical characteristics of corrosion fatigue behavior were investigated by exhibiting the distributions of crack initiation life and crack length.     

Failure analysis of drill pipe: A review

Although the drill pipe is a simple tool in the drilling industry, it is the most used and important one. The drillstring failure has two general forms: wash-out and twist-off. These failures begin with mechanical, thermal and corrosion fatigue cracks. On the basis of previously conducted researches, the failure of drillstring is not unknown. However, the occurrence of drillstring failure still is too much. The main reason for this can be due to complex loading, combined stresses and different types of vibrations and moreover, the corrosive and erosive behavior of drilling mud that makes the total condition of the well so difficult to analyze. In this paper, the attention is focused on the analysis of drill pipe failure and the fatigue crack is represented for the root cause of drill pipe failure. The aims of most of published papers are to examine how and why a specific drill pipe is failed and just the main reason of failure for that drill pipe is discussed in detail. In this paper all metallurgical and mechanical aspects of failure that can occur for a drill pipe, are considered and discussed. And finally, this comprehensive review leads to a conclusion that categorizes the primary sources of drill pipe failure into seven major groups and makes some recommendations to avoid them.