酸性油气田C110套管断裂失效分析

Analysis on Fracture Failure of C110 Casing in Acidy Oil and Gas Field

为查明酸性油气田某油井C110套管断裂失效原因,通过C110断裂失效套管断口宏观形貌、金相组织、化学成分、力学性能和腐蚀产物成分等综合分析,对酸性油气田某油井C110套管断裂原因进行了探讨。结果表明:套管不居中导致套管产生应力集中,并在套管与卡瓦咬合的第1个齿形成严重机械损伤;同时,地层运动、套压波动等因素导致套管在应力集中部位出现交变载荷。最终,在套管内壁处于高H2S、低p H值环境下,在内表面交变应力集中区域发生腐蚀疲劳开裂。

In order to find out the reason of the fracture failure of C110 casing of an oil well in acidy oil and gas field,the fracture macroscopic morphology,microstructure,chemical composition,mechanical properties and corrosion product component were studied and the fracture failure cause was analyzed. Results showed that the non-centered phenomena of the casing led to the stress concentration,and the serious mechanical damage occurred at the first biting tooth by casing and slip. At the same time,alternating loads appeared in the stress concentration position due to the stratum movement,casing pressure fluctuation and other factors. Finally,the corrosion fatigue crack occurred in the alternating stress concentration area of the inner surface under the condition of high H2 S and low p H value.