超深气井油管气密封检测应力分析及防控措施

Analysis and control measures on the air tightness detecting pressure of tubing in ultra-deep gas wells

为预防气密封检测压力不当对超深气井油管螺纹造成初始损伤,采用接触问题分析的有限元法,建立了3种型号的油管气密封检测有限元力学模型,针对塔里木油田某超深气井油管螺纹气密封检测的应力问题进行了定量、系统的研究。结果表明:当下部悬重油管重力超过一定值后,气密封检测会造成油管螺纹大端最后三扣扣跟的塑性变形,随着提拉力的增加,塑变面积也随之增加;在相同的工况下,增加油管的壁厚并不会明显改善大端最后三扣扣跟处的应力集中现象。通过改进气密封检测压力和提高油管螺纹钢级可以明显提升油管螺纹的服役安全系数,建立的模型可以为油管螺纹气密封检测应力分布规律定量地提供理论依据。

In order to prevent the initial damage to the tubing threads of ultra-deep gas wells caused by the improper pressure during air tightness detection,the finite element mechanical model of air tightness detection for three types of tubing was established by means of the finite element method which is used to analyze contact problems.Then,the stress during the air tightness detection on the tubing threads of a certain ultra-deep gas well in Tarim Oilfield was studied quantitatively and systematically.It is indicated that when the gravity of the tubing with suspending weight in the lower part exceeds a certain value,air tightness detection will lead to plastic deformation of the last three connection roots at the big end of tubing thread,and the plastic deformation area increases with the increase of the lifting force.In the same operational mode,the stress concentration at the last three connection roots of the big end cannot be improved significantly by increasing the wall thickness of tubing.The service safety factor of tubing thread can be improved significantly by modifying the air tightness detecting pressure and increasing the steel grade of tubing thread.The model established in this paper can provide the theoretical basis for quantitative study on the distribution laws of air tightness detecting stress of tubing thread.