减振器对井下钻具振动特性的影响分析

Influence of shock absorber on down-hole drilling tools' vibration characteristics

针对使用减振器后,井下钻具振动并非都能得到明显减缓、因振动引起的钻具断裂事故仍时有发生的工程难题,该文基于虚功原理并利用数值模拟技术,结合牙轮钻头在破岩过程中的力学性能和运动规律,系统地分析了减振器对井下钻具纵向和扭转振动特性的影响。通过分析获得了纵向减振器特征参数(刚度、安装位置和阻尼)对井下钻具纵向振动的影响规律;给出了不同刚度纵向减振器的最优阻尼取值范围;发现纵向减振器对井下钻具的扭转振动和纵向振动具有相似的影响,扭转减振器在减缓上部钻杆振动的同时加剧钻头扭转振动;指出在确定减振器最优特征参数时,应在考虑转速的基础上增加对钻杆和钻头振动特性的关注。该研究工作为减振器的现场使用和优化设计提供了重要的科学依据。

Down-hole drilling tools' vibration is not surely reduced significantly and fracture accidents still occur occasionally after the use of shock absorber.Based on the virtual work principle and the numerical simulation method,according to the dynamic law and mechanical property of a roller cone bit,the influence of shock absorber on down-hole drilling tools' vibration characteristics was analyzed.Firstly,the influence law of longitudinal shock absorber's characteristic parameters including stiffness,installation site and damping on down-hole drilling tools' axial vibration was obtained.Then,the optimal damping ranges of a longitudinal shock absorber with different stiffnesses were provided.The fact that a longitudinal shock absorber has the same effects on torsional vibration as those on axial vibration,while a torsional shock absorber intensifies the bit's vibration was found.Finally,the suggestion that more attentions should be paid to vibrations of a drilling string and a bit based on consideration of rotarting speed during choosing shock absorber's optimal characteristic parameters was given.The study provided a scientific basis for using and optimal design of shock absorbers.