FLEXIBLE BIT - A NEW ANTIVIBRATION PDC-BIT CONCEPT

The rigid link that exists between the bit and the bottomhole assembly (BHA) is responsible for initiating severe downhole vibrations. Intro duction of a tilt flexibility at the bit allows the decrease of the co upling between the bit and the BHA, hence improving the bit stability. The concept has been verified with a specially designed laboratory ma chine capable of creating downhole dynamic conditions. An 81/2-in. bit prototype has been designed and tested in the field. Downhole acceler ometer records demonstrate that the vibration level can be substantial ly lowered by the introduction of a flexible connection at the bit.