US 6,460,631 B2 · Drill bits with reduced exposure of cutters

Abstract

A rotary drag bit and method for drilling subterranean formations including a bit body being provided with at least one cutter thereon exhibiting reduced, or limited, exposure to the formation so as to control the depth-of-cut of the at least one cutter, so as to control the volume of formation material cut per bit rotation, as well as to control the amount of torque experienced by the bit and an optionally associated bottomhole assembly regardless of the effective weight-on-bit. The exterior of the bit preferably includes a plurality of blade structures carrying at least one such cutter thereon and including a sufficient amount of bearing surface area to contact the formation so as to generally distribute the weight of the bit against the bottom of the borehole without exceeding the compressive strength of the formation rock.

Claims83

Dependent claims

A drill bit for subterranean drilling, comprising:

a bit body including a longitudinal centerline, a leading end having a face for contacting a formation having a maximum compressive strength during drilling, and a trailing end having a structure associated therewith for connecting the bit body to a drill string, the face of the leading end configured to include a total bearing surface of a size sufficient to substantially support the bit body upon the bit body being forced against the formation at a maximum weight-on-bit resulting in a unit load on the formation not exceeding the maximum compressive strength of the formation;
and
at least one superabrasive cutter for engaging the formation during drilling secured to a selected portion of the face of the leading end of the bit body, the at least one superabrasive cutter exhibiting a limited amount of cutter exposure perpendicular to the selected portion of the face of the leading end to which the at least one superabrasive cutter is secured to, in combination with the total bearing surface of the bit body, limit a maximum depth-of-cut of the at least one superabrasive cutter into the formation having the maximum compressive strength during drilling.

A method of designing a drill bit for drilling subterranean formations, the drill bit under design including a plurality of superabrasive cutters disposed about the formation-engaging leading end of the drill bit, the method comprising:

selecting a maximum depth-of-cut for the at least some of the plurality of superabrasive cutters;
selecting a cutter profile arrangement to which the at least some of the plurality of superabrasive cutters are to be radially and longitudinally positioned on the leading end of the drill bit;
selecting an individual extent of cutter exposure to which the at least some of the plurality of superabrasive cutters are to be exposed generally perpendicular from at least one respective formation-facing bearing surface at least partially surrounding the at least some of the plurality of superabrasive cutters so as to ensure that the selected maximum depth-of-cut for the at least some of the plurality of superabrasive cutters is not exceeded;
and
including within the design of the drill bit a sufficient total amount of formation-facing bearing surface area to axially support the drill bit should the drill bit be subjected to a weight-on-bit exceeding a weight-on-bit which would cause the at least some of the plurality of superabrasive cutters to engage a subterranean formation at the selected maximum depth-of-cut.

2 more elements

Dependencies are inferred from the claim text.

Drill bits with reduced exposure of cutters

Life of this patent

Drill bits with reduced exposure of cutters

Life of this patent

Abstract

Claims83