热采转火驱生产井油管的腐蚀失效分析

采用光学显微镜,扫描电镜和能谱仪等观察分析了某热采转火驱生产井油管断口的宏观及微观形态,断裂油管的显微组织、化学成分以及腐蚀产物膜等,并结合火驱阶段现场工况条件分析了油管断裂失效原因。结果表明:油管断裂失效机理为拉伸过载失效;局部温度过高导致材料发生二次高温回火,是导致油管承载能力下降的主要原因;火驱阶段井底CO_2分压较高,导致油管内外壁产生CO_2腐蚀,CO_2腐蚀引起的壁厚减薄亦是导致油管承载能力下降的原因。

Failure Analysis of Oil Tube Corrosion in an Well Converting from Thermal Recovery Production to Fireflood Production

The macrograph and micro morphology of fracture of an oil tube in the well from thermal recovery production to fireflood production,the microstructure of fractured oil tube,chemical composition and corrosion product film were studied by optical microscopy,scanning electron microscopy and energy dispersive spectroscopy.The reasons for oil tube failure were analyzed in combination with field conditions of fire flooding stage.The results show that the mechanism of the oil tube fracture was tensile overload.Second high temperature tempering of the material caused by local high temperature was the main reason for decline in carrying capacity of the oil tube.The partial pressure of CO2 was over high during fire flooding stage in the downhole,resulting carbon dioxide corrosion in inner wall and outer wall of the oil tube.Wall thickness thinning caused by CO2 corrosion also led to the declination of carrying capacity for the oil tube.