连续油管屈曲轴向载荷研究

Research on Buckling Axial Load of Coiled Tubing

连续油管屈曲与极限载荷问题对连续油管(Coiled Tubing)井下作业会造成严重的影响,长水平段小井眼定向水平井,是制约其井底有效延伸、井筒清洁的决定性因素。连续油管在井下处在复杂的交变应力作用下会产生正弦、余弦、螺旋等系列的变化,随着连续油管在井底的不断延伸,会由一根近直杆向弯曲、螺旋、锁死等状态发展。由于受井筒及井底横向延伸约束,连续油管在井下载荷作用下的屈曲变形一直都是研究的难点。运用能量守恒法以及微分方程法建模求导发现,CT临界弯曲推导公式基本相同,结合微积分学并借助计算机根据现场数据算出CT发生正弦弯曲变形的临界轴压载荷为25.1kN。

The buckling and ultimate load of coiled tubing will have a serious impact on the downhole operation of coiled tubing. For the directional horizontal well with long horizontal section and small borehole,it is the decisive factor that restricts its effective bottom extension and wellbore cleaning.Under the complex alternating stress,coiled tubing will produce sine,cosine,spiral and other series of changes.With the continuous extension of coiled tubing at the bottom of the well,it will develop from a near straight rod to bending,spiral,locking and other states.Because of the restriction of wellbore and bottom hole lateral extension,the buckling deformation of coiled tubing under well loading is always a difficult problem.By using the method of energy conservation and differential equation,the derivation formula of CT critical bending is basically the same.Combined with calculus and computer,the critical axial load of CT with sinusoidal bending deformation is 25.1kn.