波纹管胀形有限元分析

A Finite Element Analysis of Bellows Bulging

为了分析钻井液围压、井眼曲率、弯曲方式以及地层温度等因素对波纹管胀形的影响，采用弹性力学理论，考虑几何非线性的影响，建立了波纹管胀形力学模型。建模时温度对波纹管胀形的影响通过改变波纹管管材的弹性模量和泊松比来模拟；通过对波纹管内、外施加面载荷来模拟波纹管胀形压力、钻井液围压或者外挤压力。模拟结果表明，当井眼曲率每30m在5°～12°之间变化、地层温度在20～180℃之间变化时，井眼曲率和地层温度对波纹管膨胀工作压力影响较小；弯曲方式对波纹管胀形的影响也较小。波纹管卸载后不圆度会增加，使得其内通径变小，所以在波纹管施工结束后需要进行机械胀形修正。

To analyze the eflects of the confining pressure of drilling fluid, hole curvature, bending mode and formation temperature on bellows bulging, the mechanical model of bellows bulging was established adopting the theory of elastic mechanics and considering the effect of geometric nonlinearity. The effect of temperature on bellows bulging was achieved by changing the elastic modulus and Poisson＇s ratio of the bellows material in modeling. The external and internal surface load was applied to bellows to simulate the pressure of bellows bulging, the confining pressure of drilling fluid or collapse pressure. The simulation shows that when hole curvature varies between 5°and 12°/30 m and when formation temperature varies between 20℃ and 180℃, hole curvature and temperature do not have considerable effect on the operating pressure of bellows expansion. The bending mode does not have considerable effect on bellows bulging either. The out-of-roundness will increase after bellows unloading, making its inner diameter become smaller. Therefore, the mechanical bulging revision is required after bellows construction comes to all end.