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。     

G105钻杆管体刺穿失效分析

某油田钻井公司使用的规格为φ101.6 mm×8.38 mm的G105钻杆先后发生两起管体刺穿失效事故,通过化学成分分析、力学性能测试、金相检验、X射线衍射等方法并结合钻杆的受力状态对钻杆刺穿原因进行了分析。结果表明:钻杆刺穿失效形式为腐蚀疲劳,在钻井液中腐蚀介质作用下,钻杆首先发生氧腐蚀和Cl~-加速腐蚀,使钻杆外表面产生许多腐蚀坑,并于腐蚀坑底部形成应力集中;随后在钻井过程的交变应力作用下,应力集中严重的腐蚀坑底部开始萌生裂纹,裂纹不断疲劳扩展直至穿透管壁;最终在钻杆内钻井液的冲刷作用下发生刺穿失效。     

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。     

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。     

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。     

Neuber公式应用于对接接头焊趾应力分析的修正

在平面应力和平面应变状态下,根据不同理论应力集中系数的对接接头焊趾处的应力集中系数和应变集中系数的弹塑性有限元计算结果,分析了Neuber尖缺口公式、钝缺口公式和钝缺口Sonsino修正公式的适用性,并进一步对Neuber公式进行了修正,修正表达式为Kσ+Kt2·Kε+Kt2=K2t。     

连续碳纤维混合3D打印工艺及仿生腿性能研究

基于连续与短切碳纤维复合材料双喷头混合3D打印工艺原理,本文研究了连续碳纤维在实验样条中的排布方式,对3D打印中连续碳纤维的层间布局进行工艺规划,并应用于四足机器人仿生腿的制造,以增强四足机器人仿生腿的承载能力。根据不同工况下四足机器人仿生腿的受力分析及静力学仿真结果,得到仿生腿受力时理论应力集中部位,并由此设计承载力实验对仿生腿30°外展工况持续施加力至额定载荷;通过仿生腿在承载力实验中结构失效的部位与仿真时理论应力集中处的对照分析,证明了仿真结果的准确性。依据仿生腿侧面受力时结构失效的测试评估结果,对3D打印仿生腿中的连续碳纤维的布局进行合理工艺规划,在不增大连续碳纤维整体含量的条件下对应力集中部位进行选择性增强,可在提高3D打印性价比的同时使仿生腿的最大拉升强度提升至310 MPa,从而达到更优的承载作用。     

可抛投移动机器人跌落分析及电池变形优化

目的 对可抛投移动机器人进行跌落仿真并优化电池保护结构。方法 为了承受至少跌落6 m的强大冲击力，选取EVA及碳纤维材料对抛投机器人进行抗摔设计。基于Ls-Dyna对抛投机器人的3种工况进行跌落仿真，探究机器人各部件的受力情况以及损伤的原因。同时着重对机器人的电池及其箱体结构进行跌落仿真，分析电池失效的原因，并提出整改方案。结果 表明了整体抗摔设计的有效性，没有超出设计材料的屈服点。同时，得出了电池失效的根本原因是电池材质较软以及保护结构包络面积不够，优化后的机器人的电池变形量减小了60%，电池失效得到了根本性改善。结论 经过仿真和实际抛投验证，所提优化方法可用于指导抛投和抗摔类机器人的抗摔设计。     

初、次级蚀坑三维变化对钢板应力集中系数的影响

利用ANSYS数值分析软件,首先讨论了不同半椭球体初级蚀坑深宽比对应力分布及应力集中系数的影响,得到了单调拉伸荷载作用下半椭球体蚀坑应力集中系数Kt计算模型。然后以半椭球体蚀坑为基准,通过改变蚀坑宽度或长度,建立了具有不同三维尺寸蚀坑钢材模型,分析了蚀坑宽度或长度变化对应力集中系数的影响规律,得到了单调拉伸荷载作用下蚀坑宽度或长度变化时Kt近似计算模型。最后讨论了次级蚀坑三维变化对应力集中系数的影响规律。     

Failure analysis and appropriate design of drill pipe upset transition area

In recent years, the drill pipe failures often happen in the case of ultra deep well drilling and complex geological conditions drilling. One of the main failure types is the stress concentration at the upset transition area of the drill pipe. Based on the elastic–plastic mechanics, finite element theory, and application of numerical simulation analysis for the actual mechanical properties of three-dimensional simulation analysis of drill pipe in the well, the finite element analysis (FEA) model of 5″ API standard drill pipe is established. The mechanical characteristic of API standard drill pipe upset transition area is simulated, which can provide a reasonable reference for the optimization of the size of new types 5″ drill pipe upset transition as well as the practical application. Based on the simulation model, the factors affecting the stress distribution of the drill pipe upset transition area are obtained, and the new type of upset is developed.     

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 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.     

Failure analysis of girth weld cracking of mechanically lined pipe used in gasfield gathering system

Girth weld cracking of mechanically lined pipe was occurred after 75 days operation in a gasfield gathering system in China. Failure causes were analyzed based on operation histories, field documents, and laboratory tests. Results showed that the girth weld failure was mainly due to two aspects, girth weld martensite microstructure and external stress. The crack was initiated from sealing pass zone and filling pass zone, which is a hard and brittle martensite structure with hardness of HV 350–450. The failed pipe area had undergone the heavy rain for 2 days, pulling stress, bending stress, and shear stress generated by soil movement resulted in high stress concentration at girth weld. The girth weld cracking failure was initiated from outer carbon steel, and propagated along the weld-fusion line in intergranular mode, which is a typical stress corrosion cracking failure.     

Failure analysis of ∅127mm IEU G105 drill pipe wash out

One ∅127 mm IEU G105 drill pipe body washed out infrequently just after 126 h of pure drilling time. This paper gives a systematic analysis in consideration of material quality and loading condition on drill strings. Measurement and inspection were performed on configuration, chemical composition, mechanical performance, metallography and micro-fractography. It’s thought that the drill pipe washed out accident was premature fatigue failure accident. Failure reason is the 0.35 mm decarburization layer caused by improper heat treatment and mechanical damage because of improper operating on the out surface. Under the effect of fluctuating stress, cracks originated from decarburization layer and grew rapidly. When cracks propagated through the wall thickness, drill pipe washed out.     

地质钻杆摩擦焊接组织和力学性能

探讨了地质钻杆用DZ60钢钻杆管体与40Cr钢钻杆接头的摩擦焊接性，并与采用热墩粗工艺生产的钻杆管体力学性能进行了对比。结果表明，摩擦焊接的地质钻杆具有良好的综合力学性能。     

某油田钻具失效统计分析

对某油田2002-2004年钻具失效情况进行了系统调查,查清了不同钻具的失效形式和失效次数。通过统计分析发现钻铤断裂次数最多,占钻具失效总数的比例最大。对钻铤断裂机理和受力状态进行了分析,认为钻铤断裂性质主要属于早期疲劳失效。对钻铤标准和实际使用状况进行了分析,找出了钻铤标准中存在的问题。对钻铤断裂原因从螺纹接头结构应力、残余应力和材料韧性等方面进行了分析,指出了导致钻铤断裂的产品质量问题。通过使用工况和钻井参数对钻铤的受力状态进行了分析,指出了使用操作对钻铤断裂的影响。最后对该油田依据上述结论采取措施后2009-2011年钻具失效情况进行了统计分析,发现钻具失效事故大幅度减少。