高温高压气井测试管柱的横向振动与稳定性

The transverse vibration and stability of the high-temperature and high-pressure gas-well testing pipestring

从测试管柱内的气流流动诱发管柱横向振动与管柱稳定性的角度进行了分析。根据汉密尔顿(Ham ilton)原理推导了输送天然气的测试管柱横向振动方程,给出了测试管柱横向振动频率与失稳的临界速度计算方程,并讨论了管内流体流速对管柱的振动频率和稳定性的影响。结果表明,天然气在管柱内流动对管道的振动频率和稳定性有较大影响,管柱横向振动的固有频率取决于管道的抗弯刚度EI、管道的几何参数(跨距L、过流面积A)、管内流体密度ρ和流速v,且随着管内流速v、跨距L的增加,管柱横向振动频率呈下降趋势;高温高压气井高流速作用下的实际测试管柱在井筒中可能存在多处失稳,进而导致封隔器失封、测试管柱连接螺纹松扣甚至疲劳断裂等事故。

The testing pipestring’s transverse vibration caused by the air flow and the pipestring stability were both analyzed in this paper. According to the Hamilton principle, the transverse vibration equation of the testing pipestring for natural gas transportation was derived, the critical speed calculation equation of the testing pipestring transverse vibration frequency and destabilizing was offered, and the effect of the flowrate inside the pipestring on the vibration frequency and stability of the pipestring was discussed. The result showed that the flow of natural gas in the pipestring had great effect on the vibration frequency and stability of the pipestring. The inherent frequency of transverse vibration of the pipestring was dependent on the bending rigidity EI of the pipeline, the geometric parameters of the pipeline (such as the span L and the open area A), the fluid density ρ and the flow v in the pipe. Moreover, with the increase of the flowrate v and the span L, the transverse vibration frequency of the pipestring tended to decrease gradually. The realistic testing pipestring might be destabilizing in many places under the effect of the high flowrate of the high-temperature and high-pressure gas-well, leading to such troubles as packer failure, pipestring’s connection thread getting free or even broken.