Patent ID: 6394200
Filing Date: 2002-05-28
Classification: E21B

Abstract:
A bi-center drill bit comprising a bit body, the bit body having a longitudinal axis, a first end adapted to be detachably: secured to a drill string, a pilot section on a second, opposite end of the bit body and an eccentric reamer section intermediate the first and second ends, anda plurality of cutting elements on the pilot section, a first center of rotation of the pilot section about the longitudinal axis, a radius of rotation R1 of the drill bit about the first center of rotation, a second center of rotation of the pilot section spaced apart from the first center of rotation by a distance D, a radius of rotation R2 of the drill bit about the second center of rotation, the radius of rotation R1 is less than the sum of the radius of rotation R2 and distance D, wherein a plurality of non-cutting bearing elements are mounted upon the bit body at radius R2.