新疆油田某火驱生产井在修井时发生油管柱断裂。此前，该油管先后经历了蒸汽热采、火驱两种工况。通过金相分析、微观形貌检测、能谱分析及X射线衍射分析等方法，对油管断裂原因进行了深入研究。结果表明：油管碎片表面的腐蚀产物主要有FeCO₃和Fe的硫化物；井下油管发生了CO₂腐蚀和H₂S腐蚀，管柱剩余壁厚不足，难以承受油管悬重，导致油管断裂落井；经历过蒸汽热采和火驱两种工况的N80油管，其腐蚀严重程度远高于火驱工况下的，因此在蒸汽热采井转火驱生产论证时，应客观评价原有管柱的服役能力。

An oil pipe fractured during the workover of a production well in Xinjiang Oilfield. The failed pipe experienced steam thermal recovery production and fireflood production two conditions in turn. The causes of the oil pipe fracture were studied by metallographic analysis, micro-morphology detection, energy dispersive spectrum (EDS) analysis and X-ray diffraction (XRD) analysis. The results show that the corrosion products on the surface of the failed pipe were mainly composed of FeCO₃ and Fe sulfides. CO₂ corrosion and H₂S corrosion occurred on the underground oil pipe, and the residual wall thickness of the pipe was insufficient to bear the weight of oil pipe, resulting in the fracture and collapse of the oil pipe. The corrosion of N80 oil pipe which had experienced two working conditions of steam thermal recovery production and fireflood production was severer than that under single working condition of fireflood. So the service capacity of original pipe should be evaluated objectively when oil well production converts from thermal recovery production into fireflood production.