基于复模态法的深水钻井隔水管反冲响应力学特性

考虑隔水管在正常钻井作业过程中由于轴向拉伸储存的弹性势能和反冲过程中钻井液下泄时产生的黏滞阻力的共同影响,通过将隔水管离散化为三自由度质量-弹簧-阻尼系统,建立隔水管紧急解脱后的反冲响应力学分析模型和控制方程;以浮式钻井设备的升沉运动作为边界条件,以隔水管解脱前的变形为初始条件,考虑控制方程中阻尼矩阵不能被对角化的影响,采用复模态分析法对控制方程进行求解;根据实例分析得到反冲过程中隔水管底部总成(low marine riser package,LMRP)振动位移的变化规律,并讨论水深、波高、顶部张紧器弹簧刚度及解脱相位角等因素对LMRP振动位移的影响,研究隔水管反冲响应的主控因素。结果表明:在同样的作业条件下,水深越大,隔水管紧急解脱的安全作业窗口越小;波高越大,隔水管的反冲响应越剧烈;顶部张紧器的刚度是决定隔水管反冲特性的一个重要因素,张紧器刚度越小,LMRP与防喷器发生碰撞的可能性越大;解脱相位角对隔水管的反冲特性影响不大。

Mechanical analysis on recoil response of deepwater drilling riser based on a complex mode method

In this study,a mechanical model and control equations for the recoil response of drilling riser were established by discrediting the riser as a mass-spring-damping system,in which the elastic potential energy stored in the riser due to axial tension in normal drilling operation and the viscous resistance acting on the riser during fluid discharge in recoil response were considered.The heave motion of the floating drilling vessel was taken as the boundary condition,and the riser axial deformation before disconnection was taken as the initial condition.The control equations were solved by a complex mode method considering the damping matrix in the governing equations cannot be diagonalized.Finally,the vibration displacement of the low marine riser package(LMRP)during recoil response was obtained.Then,the influence of water depth,wave height,spring stiffness of the top tensioner and disconnection phase angle on the vibration displacement of the LMRP was discussed in details.The analysis results show that,under the same operating conditions,the greater the water depth,the smaller the safe operating window of the riser emergency disconnection,and the higher the wave height,the more severe the riser recoil response.The stiffness of the top tensioner is an important factor determining the riser recoil characteristics.The possibility of collision between the LMRP and blow out preventer increases dramatically with the decrease of the stiffness of the top tensioner.While the disconnection phase angle has little effect on the riser recoil response.