油气井套管侧向屈曲分析与井下加强工具探讨

针对油气井套管挤毁的研究多局限于强度分析,忽视了套管侧向稳定性问题。除小直径或特厚壁的套管外,常用套管的失效形式应属于失稳损坏。基于外压作用下套管侧向屈曲机制,分别采用API标准和圆筒屈曲分析的方法,计算套管侧向屈曲的临界压力。另外,对减小套管计算长度的井下加强工具进行探讨和设计。结果表明:套管纵向长度对侧向屈曲的临界压力具有重要影响;若把套管的计算长度减小到某一范围,可有效地提高套管的抗失稳能力。结果为提高套管抗失稳能力提供了一种新途径,可作为完井后高挤毁风险套管的加强补救措施。

Lateral buckling analysis of oil and gas well casing and design of downhole reinforcement tool

The current researches on casing collapse are mainly confined to strength analysis, while the problems caused by lateral buckling are less considered. In fact, the most failures of oil and gas well casing, except casings with small diameter or thick wall, can be attributed to the mode of buckling failure. The mechanisms of casing buckling under external pressure were revealed. The critical pressure of casing lateral buckling was calculated using two methods, including an API standard and a cylinder buckling analysis technique. Subsequently, the downhole casing reinforcing tool was designed. The results indicate that the casing length used in the calculation has a great influence on the critical pressure for lateral buckling of casings, and the anti-instability of casings increases with the decrease of the values of casing length adopted in the calculation. The findings can efficiently increase the anti-instability of casings and provide a new remedial measure for casings with high collapse risks after well completion.