对某油田Φ139.7 mm×7.72 mm J55 LC SEW套管脱扣掉井事故进行了详细调查,分析了脱扣套管的理化性能、损伤特征,并对同批新套管进行螺纹、上卸扣、整管拉伸等实物性能进行验证试验,分析表明在失效接头外螺纹第22～23 扣根部周向位置萌生一定长度的裂纹,在高压泥浆的循环作用下,导致外螺纹从内表面向外表面形成一个局部的高压区,从而在泥浆刺漏和冲蚀下使接箍镗孔端刺穿损坏,造成套管材料强度和螺纹连接结构和强度发生改变,最终在起套管过程中因承受不了较大的拉伸载荷而发生掉井.
Failure Analysis of Casing Pullout in an Oil Field
A detailed investigation was conducted on the Φ139.7 mm×7.72 mm J55 LC SEW casing pullout and falling accident.The physical and chemical properties and damage characteristics of the dropped casing were analyzed and studied,and the physical properties of the same batch of new casing were verified through thread parameter inspection,make-up and break-out test and full section tensile test.It is considered that there is an initial crack of a certain length in the circumferential position of the 22nd to 23rd tooth of the failed external thread joint.Under the circulation of high pressure mud,a localized high pressure zone from the inner surface to the outer surface is created on the external thread joint.Thus,the boring end of the casing is punctured and damaged under mud leakage and erosion,resulting in the change of casing material strength and threaded connection structure and strength.In the end,the casing fell out because it could not bear the large tensile load in the process of casing withdrawal.
万方数据
维普
