Turbine driven reaming bit with profile limiting torque fluctuation

摘要

A reaming bit designed to operate with low torque fluctuation when driven with a turbine at speeds in the order of 300-600 RPM and above features a profile that is arcuate from the gauge dimension to the nose area or alternatively has a blunt straight taper section but with a ratio of profile length (PL) to bit size (BS) of under 0.75. The blades extend into a concave cone and the cutting structure continues along the blades towards the center. The blades have a step near the gauge section to increase the exposure of the blade cutting structure. An array of protrusions are disposed parallel to and behind the cutting structure to increase high speed stability and adjacent the blade step transition to protect outer casing on run in.

主权项

1. A high speed reaming tool for enlarging and cleaning out an existing borehole, comprising:
a tubular body; a plurality of blades extending from the body with cutting elements on the leading edge defining a profile; said profile extends from a cylindrical gage section to the center of the body and has a length (PL) that includes a central concave cone section, an arcuate nose section, a straight tapered transition and an arcuate shoulder section; said tool has a size (BS) defined by a diameter in a plane that is transverse to the central axis and intersects said gage section; the ratio of PL/BS is less than 0.75.