Patent ID: 6464024
Filing Date: 2002-10-15
Classification: E21B

Abstract:
A bi-center drill bit comprising:a body having pilot blades and reaming blades affixed thereto at azimuthally spaced apart locations, said pilot blades and said reaming blades having polycrystalline diamond compact cutters attached thereto at selected positions along each of said blades, an outermost surface of each of said reaming blades conforming to a radially least extensive one, with respect to a longitudinal axis of said bit, of a pass through circle and a drill circle, said drill circle substantially coaxial with said longitudinal axis, said pass-through circle axially offset from said drill circle and defining an arcuate section wherein said pass-through circle extends from said longitudinal axis past a radius of said drill circle, so that radially outermost cutters disposed on said reaming blades drill a hole having a drill diameter substantially twice a maximum lateral extension of said reaming blades from said longitudinal axis while substantially avoiding wall contact along an opening having a diameter of said pass through circle.