某井套管柱泄漏原因分析

某井在固井试压过程中发生套管柱泄漏事故,随后进行了找漏、挤水泥堵漏和测井检查作业,结果显示多根套管接头泄漏导致套管柱密封失效。通过综合分析套管柱泄漏特征和地面水压试验结果认为,套管柱泄漏的原因是套管接头现场上扣端上扣质量不合格,密封性能差所致。     

某油井特殊螺纹接头油管粘扣原因分析

某井特殊螺纹接头油管粘扣现象频繁发生,通过对井下起出的油管螺纹接头粘扣形貌进行检验和统计分析,并对该型未使用油管取样进行了螺纹检验和上卸扣试验,分析了油管接头粘扣的原因。结果表明:油管的抗粘扣性能符合标准要求,油管粘扣的主要原因是卸扣操作不当,最后给出了预防油管粘扣的具体措施。     

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。     

塔里木油田非API油、套管失效分析及预防

对塔里木油田非API油、套管的失效情况进行了统计分析,总结了油、套管常见的失效形式及失效原因,并针对每种失效形式提出了一定的预防措施。结果表明:套管压力升高主要是因油管接头泄漏所致,而油管接头泄漏主要是因为其气密封性能不能满足油田实际工况条件,套管挤毁失效主要与套管磨损地层蠕变有关,套管断裂和开裂既与套管材质有关,也与套管磨损有关;通过制定严格的油、套管订货技术标准,可有效预防和减少塔里木油田非API油、套管失效事故的发生。     

某井特殊螺纹套管脱扣和粘扣原因分析

对某井φ177.8mm×10.36mm 110特殊螺纹接头套管脱扣和粘扣原因进行了分析,认为套管是在严重粘扣之后才发生脱扣的,套管严重粘扣主要与下井操作不当有关。在套管起吊过程中没有螺纹保护器保护的套管接头螺纹、扭矩台肩和密封面容易被损伤,不使用对扣器直接对扣容易导致偏斜对扣;不引扣而直接开动套管钳高速上扣很容易导致粘扣和错扣;一旦严重粘扣和错扣,套管接头连接强度就会大幅度下降,最终导致套管在上提过程中发生脱扣事故。     

某高压气井特殊螺纹接头油管泄漏原因分析

某高压气井特殊螺纹接头油管发生泄漏,结合油管泄漏检查结果,采用化学成分分析、力学性能试验等方法,对油管泄漏的原因进行了分析。结果表明:油管密封面泄漏主要集中在3 900~4 869.49m井段,其中4 200~4 500m井段油管密封面全部泄漏,油管泄漏既与弯曲载荷有关,也与油管刚度有关;天然气从接箍端面渗入的油管集中在1 800~4 869.49m井段,其原因可能与温度升高之后螺纹脂性能发生变化有关,也可能与油管柱承受的载荷分布有关;多根油管接头泄漏,说明该种油管接头气密封性能不满足该井使用要求。     

高压气井不锈钢油管特殊螺纹接头工厂端泄漏和腐蚀原因分析

某高压气井完井之后套压异常升高。对该井起出的完井管柱油管接头工厂端卸扣后进行了检查和分析,发现少部分油管接头工厂端泄漏,少部分油管接头工厂端密封面粘结,部分油管外螺纹接头工厂端台肩位置内壁及内倒角消失位置腐蚀,在2 612.11～1 625.19m井段油管泄漏比例和粘结比例最高,腐蚀最严重。认为油管接头泄漏既与结构设计和上扣扭矩有关,也与油管在井下的受力状态有关;油管腐蚀说明在含有CO2和Cl-的高压气井中使用这种不锈钢材料不能防止腐蚀,油管接头位置腐蚀严重说明接头部位结构存在腐蚀集中。     

某井修复油管脱扣原因分析

塔里木油田某井在起甩射孔完井一体化管柱时,发现第43根油管现场端脱扣。脱扣油管为φ73.02mm×5.51mm修复油管,降级为N80钢级使用。为分析该油管脱扣原因,对脱扣油管及同批次修复未使用的油管取样,进行了理化检验和分析。结果表明:修复油管材料和力学性能都符合标准要求;同批次修复的油管有螺纹参数不合格和粘扣现象发生,但修复油管拉伸至失效载荷符合API TR 5C3-2008中规定的失效载荷不小于471.5kN的要求,因此螺纹参数不合格并不是导致油管脱扣的主要原因。进一步对脱扣油管宏观形貌及油管脱扣时管柱的受力情况进行分析,认为油管脱扣的主要原因是上扣过程中发生错扣,导致油管粘扣和上扣不到位,使得接头的连接强度大幅度降低,最终发生了低载荷滑脱失效。     

N80 LCSG套管上、卸扣试验研究

某油田使用的139.7mm×7.72mm N80 LCSG套管发生了粘扣事故,为搞清套管粘扣原因和套管本身抗粘扣性能,对套管的材料性能和螺纹参数等进行了检测,并用套管实物进行了上、卸扣试验。结果表明,该批套管粘扣主要原因是套管本身存在粘扣质量问题,而不是油田现场操作不当所致。对上、卸扣后套管螺纹的粘扣形貌和规律进行研究分析,认为套管抗粘扣性能差的主要原因是内、外螺纹匹配不合理及表面处理质量差所致。     

进口φ39．7mm套管在固井过程中脱扣原因分析

某井进口φ339．7mm电阻焊（ERW）套管固井事故进行了全面调查研究,通过对磁性定位测井CCL曲线反映的套管柱失效形貌和对井下捞出的套管残片形貌进行分析认为,套管柱在固井过程中发生了脱扣,脱扣位置在第5根套管的工厂连接端。通过对套管的螺纹加工、材料和上扣连接质量等进行分析和对套管柱在固井过程中的受力状态进行计算认为,套管所受栽荷远小于其连接强度,排除了过载导致套管脱扣的可能性,认为套管接头是在固井期间首先松动之后才发生脱扣的;套管接头在井下松动的原因是由于套管柱在固井过程中受到了很大的震动载荷;套管接头从工厂上扣端松动脱扣的原因主要与工厂上扣扭矩偏小有关．     

Numerical and experimental distribution of temperature and stress fields in API round threaded connection

Thread galling is one of the main failure forms for oil tubing and casing connections, and it leads to deterioration of seal performance and connection strength of oil tubing and casing directly. A series of full-scale tests were performed on samples of API J55 steel grade non-upset tubing threaded connections. The temperature and stress field distributions of the tubing threaded connection were measured dynamically under the action of different make-up and break-out torque and velocity. Major factors, which affect the distributions of temperature and stress fields of tubing connections, were studied and their effects on thread galling failure were summarized with friction-wear theory. The FEA models of tubing threaded connections are validated by comparing the numerical results with the full-scale tests. The validated models are afterwards used to perform parametric studies on the connection behaviour.     

J55长圆螺纹套管粘扣原因试验分析

某油井在下套管过程中发生了一起ф139.7 mm×7.72 mm J55长圆螺纹套管粘扣事故,为查清套管粘扣原因,结合油田套管下井上扣实际情况制定试验方案,采用全尺寸套管试样进行了上、卸扣试验。通过试验分析了各种上扣控制参量对套管粘扣性能的影响。依据试验结果推断,油田发生套管粘扣的原因既与使用操作有关,也与套管本身的质量有关。经过对油田下套管过程和实验室上、卸扣过程进行对比分析,指出了油田中在使用操作方面存在的问题。通过对套管粘扣形貌和规律进行分析,研究了套管本身的抗粘扣特性,发现了套管在螺纹加工质量方面存在的问题。     

塔里木油田套管粘扣预防及标准化

通过对塔里木油田套管粘扣原因进行调查研究和失效分析,认为套管粘扣原因既与其本身抗粘扣性能差有关,也与使用操作不当有关。油田采购的套管抗粘扣性能差与订货标准没有严格要求有关,使用操作不规范导致大量套管粘扣与没有切实可行的套管操作规范,或者操作人员没有严格执行操作规程有关。要从根本上解决套管粘扣问题,首先应当对套管粘扣原因进行失效分析和研究,找出粘扣原因,依据失效分析和研究成果制定严格的订货技术标准和操作规程,并采取一定的措施落实订货技术标准和操作规程。     

塔里木油田套管气密封检测技术现状及分析

为降低油田气井套管泄漏造成的事故风险,油田采用气密封检测技术来排查和检测完井套管的泄漏情况,保障套管的完整性,对塔里木油田气密封检测的原理、标准、现状、检测压力和检测时间进行了分析,并抽取部分检测报告对气密封检测检出套管不合格的原因进行了分析.结果表明:经卸扣、清洗、涂抹螺纹脂、排除外界干扰后再次检测,合格套管所占的比...     

非API套管接头完整性评估计算方法

针对非API套管接头的连接和密封性能提出一套完整的解析评估计算方法。首先建立具有密封和内外螺纹啮合结构的非API套管接头力学分析模型,依据API套管接头失效形式(螺纹跳扣、螺纹剪切破坏和接头断裂)及其机理结合弹塑性力学理论,推导出非API套管接头发生相应连接失效时的临界轴向载荷计算公式。然后,依据螺纹啮合对变形协调方程和单个螺纹牙轴向弹性变形分析,推导出套管接头螺纹牙啮合法向接触力计算方程组,从而获得非API套管接头各个螺纹牙轴向变形量及其承载轴向载荷分布情况数值解。最后,通过对比各个螺纹牙承载轴向载荷与连接失效临界载荷对非API套管接头进行连接性能评估;通过计算轴向载荷和气体内压作用下,套管接头螺纹轴向变形量及其对接头密封过盈配合值的影响,对非API套管接头进行密封性能评估。通过对3种典型非API套管接头完整性评估计算结果表明:在螺距、螺纹啮合中径、螺纹高度等螺纹参数相同情况下,非API套管接头的螺纹牙型设计参数(承载面角度与导向面角度)对其连接和密封性能影响显著。     

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.     

Effect of Fatigue on Proof Strength of Gas Turbine Combustor Casing

The objective of an aero-engine combustor structural design is primarily to provide the engine combustor with sufficient fatigue life and strength to permit its continuous operation until a scheduled engine overhaul and to withstand certain overload. During the service, combustor is subjected to cyclic pressure which may affect its overpressure capability. The combustor casing is considered as one of the critical parts in the engine. In this paper, the proof pressure capability of a combustor casing subjected to fatigue loading is evaluated. The effects of the fatigue damage on the proof pressure capability of the combustor casing are also established. During the testing of the casing, the pressure was continuously increased to evaluate the over pressure capability of the casing. The results of this experimental study on the casing of an aero-engine combustor are presented in this paper. A detailed post-fracture investigation of the fracture surfaces of the casing showed that two independent cracks, i.e., one along the circumference of the casing towards the front flange and the other one along the axial direction were developed. Further a detailed investigation of the fractured surface under stereo zoom microscope and scanning electron microscope showed that the presence of striations coupled with dimples indicated that the failure was initiated due to fatigue loading.