Core cutting rock bit
AssigneeSmith International, Inc.
InventorsRoger P. Johns, Gary Portwood, Gilbert S. Tyner, Charles R. Muren
Life of this patent
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Abstract
A roller cone drill bit is disclosed that leaves uncut a substantial formation core having a diameter from 10% to 25% of the bit gage diameter. The bit is designed to have normal size bearings, cone shell thickness and cutter protrusion to allow the use of standard drilling weights and RPM, thereby achieving a significant increase in drilling rate. When drilling abrasive formations, ultra hard cutting teeth are used in the cone apex to maintain the core diameter.
Claims22
A rotary cone rock bit for drilling earthen formations, the rock bit being designed to form a core while drilling a borehole for enhanced bit penetration rates, said bit comprising:
- a bit body having a first threaded pin end, a second cutter end and at least a pair of legs that support roller cutter cones rotatably retained on bearings cantilevered from an end of the legs, each of said cutter cones containing circumferential rows of individual cutters
- one or more core cutter means substantially at an apex of each cone for cutting adjacent to a central core;
- and wherein
- at least a portion of the cutters in circumferential rows extend a sufficient distance closer to a centerline of the rock bit than the core cutter means at the apex of a cone for breaking the central core.
A rotary cone rock bit for drilling earthen formations, the rock bit being designed to form a core while drilling a borehole for enhanced bit penetration rates, said bit comprising:
- a bit body forming a first threaded pin end, a second cutter end and at least a pair of legs that support roller cutter cones rotatably retained on beatings cantilevered from an end of said legs, each of said cutter cones containing circumferential rows of individual cutters, the cutters on the cones being arranged for leaving a central core having a diameter in the range of 10 percent to 25 percent of the gage diameter of the bit;
- and
- one or more core cutter means being arranged substantially at an apex of each cone for cutting the core, the core cutter means comprising a material that is harder and more abrasion resistant than the individual cutters in each of the circumferential rows of cutters on the cutter cones.
A tungsten carbide insert rotary cone rock bit for drilling earthen formations, the rock bit being designed to form a core while drilling a borehole for enhanced bit penetration rates, said bit comprising:
- a bit body having a first threaded pin end, a second cutter end and at least a pair of legs that support roller cutter cones rotatably retained on beatings cantilevered from an end of said legs, each of said cutter cones contain circumferential rows of individual cutters, the cutters on the cone being arranged for leaving a central core having a diameter in the range of 10 percent to 25 percent of the gage diameter of the bit;
- and
- one or more core cutter diamond coated inserts positioned substantially at an apex of each cone for cutting the core.
A milled tooth rotary cone rock bit for drilling earthen formations, the rock bit being designed to form a core while drilling a borehole for enhanced bit penetration rates, said bit comprising:
- a bit body having a first threaded pin end, a second cutter end and at least a pair of legs that support milled tooth roller cutter cones rotatably retained on bearings cantilevered from an end of said legs, each of the cutter cones containing circumferential rows of individual cutter teeth milled on the cone, the cutters on the cone being arranged for leaving a central core having a diameter in the range of 10 percent to 25 percent of the gage diameter of the bit;
- and
- one or more core cutter means substantially at an apex of each cone for cutting the core, the core cutter means comprising a material that is harder than the individual milled teeth in each of the circumferential rows formed on the cutter cones.
Dependencies are inferred from the claim text.