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ø73.02 mm×5.51 mm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471.5 kN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。

Thread tripping happened to the forty-third oil tube in one well of Tarim Oilfield during playing out perforated completion integrated pipe string. The tripping tube was a ø73.02 mm×5.51 mm repaired tube, which was degraded to N80 steel. The tripping tube and several unused tubes of the same repairing batch were sampled and tested physically and chemically to analyze the tripping reasons. The results show that:the material and mechanical properties of the repaired tube all met the requirements of standards; unqualified thread parameter and galling phenomenon happened to the repaired tubes of the same batch, however the tensile failure load of the repaired tubes met the requirements of API TR 5C3-2008 that the failure load should be no less than 471.5 kN, so the unqualified thread parameter was not the main reason for the tripping of the oil tube. The macro morphology of the oil tube and stress situation of the tubing string during tripping were further analyzed, it was considered that the main reason of the thread tripping was thread alternating during making-up, which made the tube galling and incompletely making up. The joint strength of the joint was greatly reduced, and a low load slip failure happened at last.