某井油管断裂原因分析

在某井抽油生产过程中,油管在表面钳牙印痕位置发生断裂。对存在钳牙印痕的油管进行了全面检查和统计分析,对钳牙印痕的产生环节和油管受力情况进行了研究。结果表明:油管在本次作业之前已被尖锐的钳牙严重咬伤,咬伤油管存在壁厚减薄和应力集中的现象,导致油管萌生裂纹并发生断裂。建议在油管上卸扣和修复过程中采用无牙痕油管液压钳进行操作。     

井下油井单根连接刺漏失效分析

采用常规理化测试手段和高温高压釜模拟试验研究了井下油井单根连接油管和接箍的刺漏失效原因。结果表明:油管和接箍的失效是由于管内介质中含有CO2和O2,导致其发生了CO2腐蚀和氧腐蚀;另外由于油管和接箍螺纹连接处存在应力集中以及井底高温和流体介质的冲刷作用,进一步加速了油管和接箍的腐蚀进程,使其管壁产生缺损,最终发生刺漏失效。     

CUI Failure of a Hot Oil Line Due to Intermittent Operations

Insulated hot oil lines on high-temperature/intermittent duty are typically vulnerable to increased risk from corrosion under insulation (CUI) failure. This paper presents the results of an investigation into a CUI failure at an onshore natural gas-processing plant and also discusses the key issues affecting intermittent duty. The inadequate coating was degraded during high-temperature duty (up to 240 °C) followed by water ingress through degraded insulation mastic and sealant and resulting in (up to 3 mm) chain (coalesced) pitting during ambient temperature downtime, at damaged coating locations from the 2 to 10 o’clock locations. Several recommendations are proposed for addressing the underlying technical and systemic causes of the failure.     

核磁共振在石油测井与地层油气评价中的应用

核磁共振（NMR）在石油测井和地层油气评价中已经得到应用,是当前地球物理勘探的前沿领域之一。介绍了NMR测井的测量原理、应用基础和地层信息的表达方式,并讨论了NMR测井的主要应用和实例。     

某稠油井用高温蒸汽注汽管爆裂失效分析

通过对某油田稠油井发生爆裂的高温蒸汽注汽管进行宏观分析、化学成分分析、金相检验、力学性能测试以及扫描电镜断口分析,找出了该管爆裂失效的原因.结果表明:该高温蒸汽注汽管线的爆裂性质为脆性开裂,开裂起源于管表面的两处机械损伤;导致其爆裂失效的主要原因是该管在服役过程中由于水击作用发生了胀径,使注汽管壁厚不均匀;同时管表面存...     

Expansion or Contraction of Slit Pores Due to Gas Uptake

Adsorption inside a slit pore of flexible width w is explored, with a focus on how w varies as a function of the external pressure P of a gas in equilibrium with the adsorbate within the pore. The analysis is first carried out in general, using a minimization of the thermodynamic grand potential energy of the system. This leads to an equation predicting both the gas uptake N as a function of chemical potential ?? and the expansion (or contraction) of the pore in response to the adsorbate??s pressure. The resulting equilibrium behavior depends on the elastic parameters of the host material. Explicit results are derived for three adsorption systems: a low density fluid, Ar (a classical fluid at finite temperature T) in a graphite pore and ⁴He within a Au pore at T=0. The resulting behaviors include some situations where the pore expands and others for which it contracts. The difference arises from the sign of the thermodynamic response of the fluid as a function of slit width.     

DN2-12井不锈钢油管酸化作业后粘扣及腐蚀原因分析

DN2-12井经过两次酸化作业之后,其不锈钢油管接头发生了严重的粘扣和腐蚀。对该井的两次酸化测试作业情况进行了调查研究,对经过酸化作业起出后的油管进行了检测分析,发现大多数油管粘扣,部分油管腐蚀。通过对油管粘扣形貌和分布规律进行宏观分析和统计分析,认为油管粘扣的主要原因是对扣和引扣操作不当所致;通过模拟腐蚀试验和对油管腐蚀形貌进行分析,认为油管接头部位存在腐蚀集中,而腐蚀集中与接头结构设计和加工精度有关;另油管腐蚀还与酸化液中的腐蚀介质和天然气中的CO2含量有关,也与油管结构和受力状态有关。     

Failure of Wheels Due to Improper Manufacturing Process

Premature cracking of wheels was observed in the prime movers used for logistic services. The fractures were located between the stud-holes and between stud-holes and hand-holes. A detailed study was carried out to investigate root cause(s) of these failures. Although chemical composition and mechanical properties of bulk material were the same, there was a difference in microstructure and hardness at the edges of stud-holes. In addition, metallography revealed the presence of burr at the circumference of the stud-holes. A number of hairline cracks and a severely distorted structure were also observed at this location. Fractography, using an SEM, confirmed the presence of sharp cracks at the root of the burr. The hardness at the edge was also higher than the bulk material. The problem was found to be due to the manufacturing process which may be inducing more work hardening and deformation than permissible at regions near the holes edges. This deformation and hardening created a material condition that led to fine cracks in this region. The resulting fine cracks grew during service under fatigue and caused premature failure of the wheels.     

Analysis of Slide Gate Mounting Bolt Failure in Steel Ladle Due to Fatigue

The mounting bolt failed during slide gate operation of a steel ladle was investigated. Metallurgical analysis confirms the bolt as IS 1367 10.9 grade high-tensile 42CrMo₄ steel. On comparative study with a good un-fractured sample, a striation of fine banded ferrite in pearlite matrix was revealed in failed bolt under optical microscopy. The bolts failed due to fatigue and crack initiated from the surface of machined bolt threads. Comparatively lower hardness, low UTS associated with lower %Cr and %Mo content found to aggravate premature failure of bolts during ladle operation. Microstructure of un-fractured sample found with tempered bainite phase. The fatigue failure of bolts occurred due to repetitive nature of shear force development during steel pouring through slide gate system. Preventive measures to reduce fatigue failure of the mounting bolts are proposed.     

某海上注水井N80油管腐蚀穿孔失效分析

通过宏观分析、理化性能分析、金相分析、XRD分析、扫描电镜微观形貌分析和能谱分析、水质和细菌测试、有限元分析等方法,并结合实际现场工况,对海上某注水管柱在底部配水器下方发生局部腐蚀穿孔的原因和机理进行分析。结果表明：该油管是垢下细菌腐蚀导致的内腐蚀穿孔,酸化作业后残酸中的高Cl^-加速了局部腐蚀穿孔,据此提出采用定期投加药剂和采用耐蚀管以防止油管早期腐蚀穿孔失效的建议。     

气井用套管螺纹接头失效分析

针对某气田开采井使用的N80钢级套管在下井后保压过程中出现的泄压事故,通过对失效接头进行了宏观观察、管材力学性能和化学成分分析,并对同批次未使用的套管接头进行了螺纹参数及外观检验,综合现场施工情况对螺纹接头失效的原因进行了分析。结果表明:产品存在缺陷和上扣扭矩过大是螺纹接头失效的原因,并提出了保证气井用套管使用安全的建议。     

某单井管道失效原因分析

利用扫描电子显微镜(SEM)、能谱仪(EDS)和水介质模拟软件(OLI)等手段对单井管道出现的腐蚀失效问题进行了分析。结果表明:失效管道材质满足GB/T 699-2015的要求,管道内表面存在有由FeCO3、CaCO3等物质组成的腐蚀产物层,腐蚀产物的不均匀分布导致管道发生垢下腐蚀,并在CO2-H2S-Cl-介质的促进作用下,导致管道腐蚀穿孔。建议定期开展清管作业,并使用配套的清管缓蚀剂进行防护。     

Failure Analysis of a Jacking Oil Pump

Some jacking oil pumps failed during operation at various thermal power plants. The failure process eliminated the use of fractography to identify the mode of fracture. Extensive tests were carried out on failed pumps, which showed that the failures were due to rubbing of the impellers     

Failure Analysis of a Gas Well Tubing due to Corrosion: A Case Study

In this study, failure analysis of a gas tubing string was investigated. Visual inspection of the tubing string showed that some of the tubings were corroded locally at pin thread ends, which resulted in abrupt replacement. In order to determine the cause of failure, chemical composition, mechanical strength, Charpy impact, and hardness, and microstructures of the corroded and non-corroded pins were investigated. The chemical composition of the tubing material was found to be API 5CT Grade C-75-2. The samples taken from the body of both the corroded and non-corroded tubings showed the same impact energy, yield strength, ultimate tensile strength, and elongation. In addition, the hardness of the body and thread ends of tubings were the same except for corroded tubings, which showed locally more hardness at thread region. Our analyses indicate that cold working the tube strings, during the make-up process in the field, caused localized corrosion of the male pins.     

Cast Iron Casing Cracking Due to Chunky Graphite Formation

Quality inspection of heavy turbomachinery casings made of ductile cast iron has revealed anomalies in the form of characteristic relief pattern on roughly machined surfaces. Detailed microstructural observations determined that this anomaly is related to degeneration of cast iron microstructure where undesired chunky graphite was formed instead of evenly dispersed graphite nodules. Mechanical tests showed that this microstructural alteration led to deterioration of mechanical properties, especially plasticity. Regularity was found as this problem affected mainly thick sections of casts, especially where the cooling rate was limited. This article discusses the consequences of chunky graphite formation, detection methods, acceptance criteria, and preventive actions.     

Failure of the J79 Engine Compressor Blade Due to Stall

The fractured and damaged compressor rotor blades of a J79 engine have been examined. Optical, stereoscopic, microhardness testing, and SEM examinations were carried out to find out the causes of the fracture. The material of the blades was STS403 and blades were used without coating. From the 15th through the 17th compressor stages the rotor blades, stator vanes, combustion, and turbine sections were damaged. The fractured surface of the 17th blade show multiple origins, secondary cracking in the blade’s convex surface, and extensive propagation before separation and rougher surfaces. The metallographic analysis of the microstructure suggested work hardening. Based on the results, the cause of the fractured blade was high-amplitude fatigue, due to severe stall. After normal engine usage of 5 months, the blade fractured and blade fragments hit the other compressor blades, stators, and casing, and caused damage in both combustion and turbine sections.     

集输管内腐蚀失效原因分析

对某站原油外输管线的内腐蚀穿孔管段进行了取样分析,使用光学显微镜、X射线衍射仪、能谱分析仪等设备对管子腐蚀形貌进行观察,发现腐蚀产物中有不同类型的羟基氧化铁以及FeCO3和FeS等,分析了导致管子电化学腐蚀穿孔的主要原因,对杂散电流和氯离子加速腐蚀穿孔的机制进行了深入的探讨,并对该类腐蚀防护提出了建议。     

Failure Analysis of a Locomotive Engine Oil Pump Shaft

In this study, the fracture of a locomotive engine oil pump shaft is investigated. According to the reports, all oil pump shafts of this type fail in short periods of time due to the fracture at a location on the shaft which is in contact with a pinion. Stress analysis showed that the shaft bears torsion and cyclic bending stresses in the fracture site. The fracture surface observations revealed that the cracks are generated from the surface, and fatigue fracture occurs due to the cyclic bending stresses. According to the laboratorial analysis, the shaft is a surface-hardened low alloy steel. The lack of suitable pre-heat treatment and surface hardening and the roughness created by the slippage between the shaft and the pinion are concluded to be responsible for the failure of the oil pump shaft.     

Failure Analysis of Well-Logging Steel Wire in a Gas Injection Well

Journal of Failure Analysis and Prevention - The fracturing of well-logging steel wire occurred during downhole operation in a gas injection well in China. The failed well-logging steel wire...