复杂力学环境中完井管柱屈曲行为及其防控措施

Buckling Behavior of Completion String in Complex Mechanical Environment and Preventive Measures

复杂力学环境中完井管柱由于处于超高温、高压的环境下,容易发生管柱屈曲,大大影响了管柱的服役寿命。基于弹塑性力学理论建立了实际井况下油管柱屈曲行为分析的有限元力学模型,并在此基础上分析了复杂力学工况下管柱的屈曲形态、横向位移等,再针对加扶正器、优化产量以及伸缩管的设计等缓解管柱屈曲措施对管柱屈曲行为的影响程度开展了研究。结果发现:在苛刻工况下,油管柱底部易发生较为复杂的屈曲,从井深5500~7300 m井段的油管柱产生了螺旋屈曲的构型,整段屈曲段长达2400 m;本文工况下,伸缩短节数达到6个后,全井段油管柱的屈曲段长度和管柱弯曲应力的减小速率大幅降低,伸缩短节的个数对管柱屈曲及弯曲应力影响大幅减弱。对于复杂环境下气井工况而言,控制产量对管柱屈曲行为改善最为明显,其次为扶正器设计,为提高油管柱寿命及气井完整性提供了技术支撑。

The completion string is easily bent due to its high temperature and pressure in complex mechanical environment,which greatly affects its service life.Based on the theory of elastic-plastic mechanics,a finite element mechanical model was established to analyze the buckling behavior of the tubing string under the actual well conditions,and the buckling shape was analyzed on this basis,and the lateral displacement of the tubing string under the complex mechanical conditions were analyzed.Meanwhile,the influence of the buckling measures of the tubing string on the buckling behavior of the tubing string were studied,such as adding centralizer,optimizing production and the design of expansion tube.The results show that under severe conditions,the bottom of the tubing string is prone to more complex buckling.The tubing string from 5500 m to 7300 m depth has a spiral buckling configuration,and the whole buckling section is 2400 m.Under this condition,when the length of the expansion joint reaches 6 m,the reduction rate of the length of the buckling section of the tubing string and the bending stress of the tubing string is greatly reduced,and the length of the expansion joint has a significant impact on the pipe.The influence of buckling and bending stress of columns is greatly weakened.For the gas wells,the control of production rate of improving the buckling behavior of the string in complex environment changes the most greatly,followed by the centralizer design.The research provides technical support for improving the life of the string and the integrity of the gas wells.