基于钻井工况和海洋环境耦合作用下的隔水管动力学模型

A dynamic model of marine risers/pipes under the drilling operation condition and sea environment

对于深水和超深水钻井,钻井工况对隔水管动力学行为的影响是一个不可忽视的问题。为此,结合我国自主建造的第一座深水钻井平台——"海洋石油981"钻井平台结构和隔水管系统的实际生产环境,利用最小势能原理,结合泛函求极值方式在国内外首次建立了基于海洋环境和钻井工况耦合作用下的隔水管系统动力学控制方程,给出了相应的边界条件、求解方法,编制了相应的计算程序,并通过实验验证了该模型的有效性。利用该模型编制了计算程序,分析了钻井工况对隔水管系统的模态及横向振幅的影响。结果表明:钻井液流速对隔水管的振动模态影响不明显;钻杆、顶张力对隔水管横向振幅的影响较为显著,顶张力越大,隔水管横向位移越小,但顶张力过大会增加隔水管的自振频率;钻杆则有可能造成隔水管局部的碰撞破坏。

As for deep and ultra-deep sea drilling, the impact of drilling condition under sea environment will never be overlooked on the dynamic responses and behaviors of marine risers/pipes. This paper presented a case study of the semi submersible offshore drill- ing rig HYSY 981, also known as ＂Offshore Oil 981＂, which is the first and only deep-water rig designed and built in China. Based on this rig＇s structure and the marine riser＇s actual working conditions, the principle of minimum energy potential integrating with the method of finding extremum of a functional was employed to establish the first kinetic responses model of marine risers under the sea drilling conditions. Meanwhile, with the given related boundary conditions and solutions, the corresponding calculating program was worked out. This model was validated by experiments and the effects of drilling operation condition were analyzed on the vibra- tion modes and lateral amplitude of the riser＇s vibration system by use of the calculating program. The following findings were concluded. The drilling fluid flow speed has little impact on the riser＇s vibration modes, but the impacts of drill pipes and top tension are noticeable on the riser＇s lateral amplitude. The greater the top tension, the smaller the lateral displacement, however, the overlarge top tension will increase the riser＇s natural frequency and drill pipes may cause local collision damage on the marine riser.