冲击载荷作用下套管螺纹连接的有限元分析

Finite Element Analysis of Casing Thread Connection under Impact Load

套管振荡器在振动固井过程中,会对套管产生周期性冲击,可能会引起套管损坏,而螺纹连接是套管柱中最薄弱的环节,有必要进一步对冲击载荷作用下的套管螺纹连接应力场进行研究。以API?139.7 mm×7.72 mm N80钢级的圆螺纹套管的螺纹连接部分为研究对象,分析了套管螺纹连接部分的应力强度和在冲击载荷作用下螺纹连接部分的应力分布规律。研究结果表明:在上扣扭矩、轴向拉伸和内压等复合载荷作用下套管内、外螺纹接触应力均出现两头高中间低的分布状态;随着上扣扭矩的增加、轴向拉应力的加大和内压的增高,套管螺纹连接部分整体Von Mises应力均呈现升高的趋势;螺纹牙承载侧的接触压应力要普遍高于导向侧;套管振荡器对套管的周期性冲击不会造成破坏。所得结论可为有冲击载荷作用的振动固井技术提供理论支持。

Casing oscillators can cause periodic impact on the casing during vibration cementing, which may cause damage to the casing. Considering the casing thread connection is the weakest part in the casing string, it is necessary to study the casing thread connection stress field under the impact load. Taking the round thread of API 0139. 7 mmx7. 72 mm N80 steel grade casing as study object, the stress of the casing thread and the stress distribu-tion of the casing thread under impact load have been analyzed. The results indicate that the contact stress of the inner and outer thread of the casing under the loads of makeup torque, axial tension and internal pressure show high values at the two ends and low values at the middle part. With the increase of the makeup torque, the axial tensile stress and the inner pressure, the Von Mises stress of the casing thread increases. The contact compressive stress on the load side of the thread is generally higher than that on the guide side. The cyclic impact of the casing oscillator will notcause casing damage. The conclusion could provide theoretical support for vibration cementing with impact loads.