BI-CENTERED DRILL BIT HAVING ENHANCED CASING DRILL-OUT CAPABILITY AND IMPROVED DIRECTIONAL STABILITY

摘要

A bi-center drill bit is disclosed which includes a bit body having pilotblades andreaming blades distributed azimuthally around the body. The blades havecuttingelements disposed thereon at selected positions. The body and blades define alongitudinal axis of the bit and a pass-through axis of the bit. In oneaspect, selectedones of the pilot blades include thereon, longitudinally between the pilotblades and thereaming blades, a pilot hole conditioning section including gage faces. Thegage facesdefine a diameter intermediate a pilot hole diameter and a pass-throughdiameter defined,respectively, by the pilot blades and the reaming blades.