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US 6,729,420 B2Granted
Multi profile performance enhancing centric bit and method of bit design
AssigneeSmith International, Inc.
InventorGraham Mensa-Wilmot
Life of this patent
Estimating the term…
Abstract
A novel drill bit includes a cutting reamer portion that cuts to gage diameter, and a pilot portion that cuts to a radius about 50%-80% of the reamer portion. The pilot portion extends downward from the reamer portion to create a distinct cutting area including pilot. The torque and weight on bit is evenly distributed between said pilot portion and said reamer portion of said drill bit by iterative adjustment of criteria such as backrake, siderake, cutter height, cutter size, and blade spacing.
Claims29
A drill bit, comprising:
- a drill bit body having a pin end and a cutting end and defining a longitudinal axis;
- a reamer portion connected to said cutting end of said drill bit body;
- a first set of cutting elements mounted to said reamer portion, said first set of cutting elements defining a reamer cutting radius;
- a pilot portion connected to and extending from said reamer portion, said pilot portion defining a pilot shoulder;
- a second set of cutting elements connected to said pilot portion, said second set of cutting elements defining a pilot cutting radius less than said reamer cutting radius;
- wherein the weight on bit and torque is about evenly distributed between said pilot portion and said reamer portion of said drill bit.
3 more elements
A method for designing a drill bit, comprising:
- a) establish a pilot portion to reamer portion cutting ratio of 0.5 to 0.8 for a drill bit having a reamer portion on the face end of a drill bit body and a pilot portion extending from said reamer portion;
- b) independently balancing said pilot portion such that the radial and circumferential forces exercised by said pilot portion during drilling will be less than 5% of the force applied along the longitudinal axis of the drill bit;
- c) balancing the drill bites a whole such that the radial and circumferential forces exercised by said drill bit during drilling will be less than 5% of the force applied along the longitudinal axis of the drill bit and further wherein the torque and weight on bit is distributed about evenly between said pilot portion and said reamer portion.
The face end of a drill bit, comprising:
- a) establish a drill bit design with a reamer portion on the face end of a drill bit body and a pilot portion extending from said reamer portion;
- b) provide stress equivalency between said reamer portion and said pilot portion by adjustment of one or more of average backrake and average cutting element size, the average backrake of cutting elements on said reamer portion being greater than or equal to said average backrake of cutting elements on said pilot portion and the average size of said cutting elements on said reamer portion being larger than or equal to the average size of said cutting elements on said pilot portion.
- c) independently balance said pilot portion such that the radial and circumferential forces exercised by said pilot portion during drilling will be less than about 5% of the force applied along the longitudinal axis of the drill bit;
- d) balancing the drill bit as a whole such that the radial and circumferential forces exercised by said drill bit during drilling will be less than about 5% of the force applied along the longitudinal axis of the drill bit and further wherein the torque and weight on bit is distributed about evenly between said pilot portion and said reamer portion.
1 more element
Dependencies are inferred from the claim text.