充满液体的圆筒中受压屈曲杆柱旋转实验

Experiment on the rotation of compressional buckling column in the liquid-filled cylinder

在钻井过程中,下部钻柱的主要运动形式为受压屈曲后的自转和涡动。受压屈曲钻柱旋转可以增大钻柱与井壁的接触摩擦力,诱发钻柱横向振动和涡动,造成井壁失稳和钻柱损坏,甚至造成钻井作业失败。目前,井筒中受压屈曲旋转钻柱的运动规律的认识尚不全面甚至部分认识是错误的。通过实验研究了载荷、转速、钻井液和圆筒内径等参数对圆筒中的受压屈曲杆柱旋转运动的影响。分析了模拟钻柱在液体中由正向涡动转为自转和反向涡动的耗散能量。结果表明:(1)随着载荷的增大,屈曲钻柱首先正向涡动;其次既有正向涡动,又有自转;然后沿部分井壁反向涡动和自转的组合;最后沿井壁反向涡动。(2)钻井液的动力润滑作用可以减小钻柱正向涡动旋转幅值,并能阻止反向涡动的形成。(3)提高钻井液的动力润滑性、减小井眼直径、增加井斜角,出现反向涡动的载荷增大。(4)钻柱随载荷增加可能出现2次反向涡动。(5)钻柱运动状态转换符合最小耗散功率原理。

In oil drilling,the main movement of the lower drill string is shown as rotation and whirl after compressional buckling.The rotation of drill stem under compressional buckling can increase the frictional force between drill stem and borehole wall,trigger the transverse vibration and whirl of drilling stem,cause borehole instability and the damage of drill string,and even lead to the drilling failure.At present,the research on the motion laws of rotary drill string in the boerhole under compressional buckling is incomplete and even some understandings are wrong,thus requiring further improvement.In this study,the influences of load,rotational speed,drilling fluid,cylinder inner diameter and other parameters on the rotary movement of compression buckling column in the cylinder were studied by experiments,so as to analyze the dissipated energy of simulated drill string in the liquid from forward whirl to rotation and backward whirl.The results indicate that:(1)With the increase of load,the buckling drill string first shows forward whirl,followed by forward whirl with rotation,then evolves to backward whirl and rotation along apart of well wall,and finally presents backward whirl along boerhole wall.(2)The dynamic lubrication of drilling fluid can reduce the rotation amplitude of the forward whirl of drill string,and the backward whirl can be prevented.(3)Through improving the dynamic lubrication of drilling fluid,increasing the well deviation angle,and decreasing the borehole diameter,the load of backward whirl is increased.(4)Twice backward whirl of drill string may occur with the increase of the load.(5)The motion state transition of drill string conforms to the theory of minimum power dissipation rate.