Development of Whirl Resistant PDC Bits

ABSTRACT The destructive effects of the dynamic forces typically induced by bit whirl have beert identified in previous works. The material presented deals with innovative design features recently developed for PDC bits which resist initiation and propagation of bit whirl. As stated in previous work, bit whirl can be initiated by both cutter/rock interaction forces and extraneous factors such as formation characteristics and undesirable BHA motions. Previous work has also shown how conventional PDC bit technology provides little resistance to whirl and in many cases may reinforce whirl once initiated. Several PDC bit features have been identified that improve bit stability. Cutter force balancing, bit asymmetry, gage design, bit profile, and cutter configuration and arrangement can all contribute to eliminating the propagation of whirl. All of these features will be investigated and assessment of their benefits reported.