| 摘要 |
<p>PCT No. PCT/GB97/00682 Sec. 371 Date Apr. 19, 1999 Sec. 102(e) Date Apr. 19, 1999 PCT Filed Mar. 12, 1997 PCT Pub. No. WO97/36191 PCT Pub. Date Oct. 2, 1997A drill string assembly containing a section of tube with a first end. The first end directly, mechanically links a drill pipe to a drill bit and transmits rotational forces from the drill pipe to the drill bit during drilling. A spring is connected to the section of tube at a point remote from the first end of the section of tube. A mass is connected to the spring such that the mass can vibrate on the spring in an axial direction relative to the section of tube and drill string. The value of the mass and the stiffness of the spring being selected such as to cause them to act as a mechanical filter and damp longitudinal compression waves at a predetermined frequency of frequency band and received at the first end of the section of tube.</p> |
