高压气井完井管柱的流固耦合振动模型及其应用

瞬态压力冲击诱发充液管道结构耦合振动，剧烈的振动将导致管道结构失效。笔者将进一步阐明天然气的瞬变流动诱发高压气井完井管柱的耦合振动过程。根据充液管道流固耦合振动模型,推导了适用于气井完井管柱的流固耦合振动四方程模型，采用特征线法及线性插值方法进行数值求解。以现场一口高压气井井口阀门开启过程中的瞬态响应为例，结合完井管柱系统的初边值条件，利用MATLAB语言编制了相应的计算机程序，计算分析了流体与管柱的耦合振动响应过程。计算结果表明：天然气的瞬变流动通过泊松耦合效应诱发完井管柱轴向往复运动，轴向往复运动将加剧完井管柱结构的疲劳破坏与磨损破坏。该结果对预防完井管柱先期失效有实际工程意义。

A fluid-solid coupled oscillation model for completion string and its application in high pressure gas well

Transient pressure fluctuations in a liquid-filled pipe could induce coupled oscillations of pipe structures, even a structural failure if severe. The present paper elaborated the coupled oscillation process of completion string induced by transient flow of natural gas, and a fluid-solid coupled oscillation four-equation model applicable to completion string in gas wells was derived based on the fluid-solid coupled oscillation model for liquid-filled pipes. The model was numerically solved by the characteristic method and linear interpolation. Taking a transient flow caused instantaneously by opening the valve of a high-pressure gas well as an example, a corresponding software, combined with initial and boundary conditions, was programmed with the MATLAB code, which could calculate and analyze the process in response to coupled oscillations derived from fluid and pipe string. The calculation indicated that the transient flow of natural gas could induce an axial reciprocation of completion string by the Poisson coupling effect, which would aggravate the structural damage of completion string via stress fatigue and rubbing abrasion. This result is, to some extent, of engineering significance in preventing completion string of high-pressure gas wells from pre-failure.