地层测试管柱力学分析

Mechanical analysis of pipe string in formation testing

地层测试是油气田勘探和开发的重要过程。在地层测试过程中,测试管柱在多种载荷作用下,形成复杂的应力和应变,有时会引起管柱的屈服破坏、断脱破坏或发生永久性的螺旋屈曲,造成较大的经济损失。根据地层测试作业过程,考虑井眼轨道、测试管柱的组成、井内流体的性能、管柱内外压强、管柱与井壁的摩擦系数、地温梯度、空气温度、油管温度、测试阀的类型、封隔器的类型、封隔器的活塞效应、管柱螺旋失稳效应等参数,建立了测试管柱在整个作业阶段的力学分析数学模型,并用差分法求解,给出沿整个管柱的拉力、扭矩、应力、安全系数、稳定性、伸长等参数。用Visual Basic2008编制了计算软件,并进行了现场应用。

Formation testing is an important procedure in oil-gas exploration and development.During which,pipe string may produce complicated stress and strain under actions of manifold loads,sometimes it may even suffer from yield failure,break or permanently helical buckling,resulting in severe economic loss.On the basis of operating procedures of formation testing,mathematical models for mechanical analysis during the whole testing operation were established by taking various parameters into account,such as wellbore trajectory,composition of pipe string,property of borehole fluid,internal and external pressure intensity,friction coefficient between pipe string and well wall,geothermal gradient,air temperature,tubing temperature,test valve type,packer type,piston effect of packer,helical buckling effect of pipe string,etc..These mathematical models were solved with the difference method,providing various parameters of pipe string,such as tension force,torque,stress,safety factor,stability and elongation.In addition,a soft ware for mechanical analysis of pipe string in formation testing was programmed using Visual Basic 2008 and applied to field operations.