METHODS AND APPARATUS FOR ATTENUATING DRILLSTRING VIBRATIONS

Apparatus and methods are described for highly attenuating vibrations of a drillstring assembly while drilling. In one embodiment, vibrations are att enuated by introducing one or more vibration attenuation modules at appropri ate assembly locations. For example, vibration attenuation modules may be in serted at locations where vibration energy is expected to be maximal. In one embodiment the vibration attenuation modules include cavities loosely packe d with particles of solid material such as sand or metallic powder. In one e mbodiment, the cavity walls are rough and/or include geometric features that enhance vibration energy transfer to the loosely packed particles in the ca vity(ies). The vibration energy is dissipated via friction and inelastic par ticle-particle and particle-wall collisions that occur as a result of drills tring motion.