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石油钻井现场对井下钻柱纵向振动的控制普遍使用了井下减振器，利用隔振原理来降低钻柱振动。文章采用钻柱的连续系统振动模型，对井下减振器的作用进行了分析，指出减振器的效果与钻压无关，而主要决定于减振器的刚度及钻柱纵向振动的激振频率；任一种减振器的使用在大多数情况下都有一定效果，但刚度越小，效果越好；在每一种减振器的使用过程中，随着钻柱的不断加长，减振器的减振效果也在不断的变化，并有可能在谐振作用下产生共振，此时减振器的使用加大了钻柱的振动而需改变钻井工艺参数以避免。因此，我们对采取吸振原理的新型减振器进行了研究并在文中予以介绍。该减振器利用附加在钻铤外面的吸振系统的振动来吸收钻柱所承受的井下激振力。附加系统质量越大，受到激励后的振幅越大，对钻柱的减振作用越显著。

Effect Analysis of Damper and a Novel Vibration Absorber

The downhole dampers in light of the vibration isolation principle to reduce the vibration of drilling string have been commonly used for controlling the longitudinal vibration of downhole drilling string in the process of drilling.In the paper,the effect of the downhole damper is analyzed according to the continuous system vibration model of drilling string;it is pointed out that the effect of the damper is irrelative to WOB but is mainly dependent on the rigidity of the damper and the exciting frequency of the longitudinal vibration of drilling string;a certain effect can be found in the use of any damper in most circumstances,however the smaller the rigidity,the better the effect;and in the process of using each damper,along with an unceasing lengthening of drilling string the amortization effect of the damper is also uninterruptedly changed and a covibration may be formed under the action of resonance;and at this time,the utilization of the damper can increase the vibration of drilling string,which may be avoided through revising the technological parameters of drilling.A novel vibration absorber of adopting vibration absorption principle has been studied,which is introduced in the article.This absorber can absorb the downhole exciting force acting on drilling string through the vibraton of absorbing system added on the surface of drill collar.And the larger the mass of the additional system,the greater the amplitude formed after exciting,the more obvious the amortization effect on drilling string.