Combination shear and gouging cutting element and well construction tools made therewith
A cutter for a well construction tool has a cutting structure affixed to a substrate, which defines a monotonically decreasing diameter with respect to an axial distance from an interface between the cutting structure and the substrate. A shear surface formed in the cutting structure intersects a surface of the cutting structure between the interface and an apex of the cutting structure, and defines a smaller angle with respect to a reference than the cutting structure proximate the interface and a larger angle with respect to the reference than the cutting structure proximate the apex. The apex is rotationally symmetric about a centerline of the cutting structure in all rotational directions, and a radius of curvature of the apex is at most 75 percent of a diameter of the substrate. A well construction tool includes a tool body with at least one such cutter attached to the tool body.
1 . A cutter for a well construction tool, comprising:
a cutting structure affixed to a substrate, the substrate made from metal carbide or steel covered with metal carbide, the cutting structure made from polycrystalline diamond, (PCD), diamond monolith, cubic boron nitride (CBN), diamond impregnated carbide, or diamond impregnated alloy, the cutting structure defining a monotonically decreasing diameter with respect to an axial distance from an interface between the cutting structure and the substrate; and
a shear surface formed in the cutting structure, the shear surface intersecting a surface of the cutting structure between the interface and an apex of the cutting structure, the shear surface defining a smaller angle with respect to a centerline of the cutter than the cutting structure proximate the interface, the shear surface defining a larger angle with respect to the centerline of the cutter than the cutting structure proximate the apex;
wherein the apex is rotationally symmetric about a centerline of the cutting structure in all rotational directions; and
wherein a radius of curvature of the apex is at most 75 percent of a diameter of the substrate.
2 . The cutter of claim 1 wherein the radius of curvature of the apex is at most 50 percent of a diameter of the substrate.
3 . The cutter of claim 1 wherein the radius of curvature is at most 25 percent of a diameter of the substrate.
4 . The cutter of claim 1 wherein the shear surface comprises a first planar subsurface intersecting the cutting structure proximate the apex, the first planar subsurface oriented at the larger angle, the shear surface comprising a second planar subsurface intersecting the cutting structure proximate the interface, the second planar subsurface oriented at the smaller angle.
5 . The cutter of claim 4 further comprising a chip breaker feature disposed intermediate intersection of the first planar subsurface with the cutting structure and intersection of the second planar subsurface with the cutting structure, the chip breaker feature disposed intermediate lateral intersections of the first planar subsurface with the cutting structure and lateral intersections of the second planar subsurface with the cutting structure, the chip breaker feature extending outwardly from the first planar subsurface and the second planar subsurface.
6 . The cutter of claim 5 wherein an amount of outward extension of the chip breaker feature is related to a distance away from the lateral intersection of the first planar subsurface and the second planar subsurface on one side of a laterally intermediate point on the chip breaker feature and a distance away from the lateral intersection of the first planar subsurface and the second planar subsurface on an opposed side of the intermediate point.
7 . The cutter of claim 6 wherein the intermediate point is disposed mid way between the lateral intersections of the first planar subsurface with the cutting structure and lateral intersections of the second planar subsurface with the cutting structure.
8 . The cutter of claim 1 further comprising at least one flow channel formed in the cutting structure between the apex and the interface on opposed lateral flanks of the cutting structure, the at least one flow channel having a radius of curvature and depth of cut so as to intersect each lateral flank at less than a full diameter of the cutting structure at a respective longitudinal position along a centerline of the cutting structure.
9 . The cutter of claim 8 wherein the at least one flow channel on the opposed lateral flanks subtends an oblique angle with respect to the centerline.
10 . The cutter of claim 9 wherein the subtended angle corresponds to an angle subtended between the centerline and an axis of rotation of a tool body to which the cutter is attached.
11 . The cutter of claim 8 wherein the shear surface comprises a first planar subsurface intersecting the cutting structure proximate the apex, the first planar subsurface oriented at the larger angle, the shear surface comprising a second planar subsurface intersecting the cutting structure proximate the interface, the second planar subsurface oriented at the smaller angle, the shear surface further comprising a chip breaker feature intermediate intersection of the first planar subsurface with the cutting structure and intersection of the second planar subsurface with the cutting structure, the chip breaker feature disposed intermediate a lateral intersection of the first planar subsurface with the cutting structure and a lateral intersections of the second planar subsurface with the cutting structure, the chip breaker feature extending outwardly from the first planar subsurface and the second planar subsurface.
12 . The cutter of claim 11 wherein an amount of outward extension of the chip breaker feature is related to a distance away from the lateral intersections of the first planar subsurface and the second planar subsurface on one side of a laterally intermediate point in the chip breaker feature and a distance away from the lateral intersections of the first planar subsurface and the second planar subsurface on an opposed side of the intermediate point.
13 . The cutter of claim 12 wherein the intermediate point is mid way between opposed lateral intersections of the first planar subsurface and the second planar subsurface.
14 . A well construction tool, comprising:
a tool body; and
a plurality of cutters attached to the tool body, at least one of the plurality of cutters comprising a cutting structure affixed to a substrate, the substrate made from metal carbide or steel covered with metal carbide, the cutting structure made from polycrystalline diamond, (PCD), diamond monolith, cubic boron nitride (CBN), diamond impregnated carbide, or diamond impregnated alloy, the cutting structure defining a monotonically decreasing diameter with respect to an axial distance from an interface between the cutting structure and the substrate, and a shear surface formed in the cutting structure, the shear surface intersecting a surface of the cutting structure between the interface and an apex of the cutting structure, the shear surface defining a smaller angle with respect to a centerline of the at least one cutter than the cutting structure proximate the interface, the shear surface defining a larger angle with respect to the centerline than the cutting structure proximate the apex, wherein the apex is rotationally symmetric about a centerline of the cutting structure in all rotational directions, and wherein a radius of curvature of the apex is at most 75 percent of a diameter of the substrate.
15 . The well construction tool of claim 14 wherein the tool body comprises one of a drill bit body, a reaming tool body and a mill body.
16 . The well construction tool of claim 14 wherein the radius of curvature of the apex is at most 50 percent of a diameter of the substrate.
17 . The well construction tool of claim 14 wherein the radius of curvature is at most 25 percent of a diameter of the substrate.
18 . The well construction tool of claim 14 wherein at least a second one of the plurality of cutters comprises a shear cutter.
19 . The well construction tool of claim 14 wherein the at least one of the plurality of cutters is mounted to a post formed in the tool body.
20 . The well construction tool of claim 14 wherein the at least one of the plurality of cutters is mounted to a blade formed in the tool body.
21 . The well construction tool of claim 14 wherein the shear surface comprises a first planar subsurface intersecting the cutting structure proximate the apex, the first planar subsurface oriented at the larger angle, the shear surface comprising a second planar subsurface intersecting the cutting structure proximate the interface, the second planar subsurface oriented at the smaller angle.
22 . The well construction tool of claim 14 further comprising a chip breaker feature intermediate intersection of the first planar subsurface with the cutting structure and intersection of the second planar subsurface with the cutting structure, the chip breaker feature disposed intermediate lateral intersections of the first planar subsurface with the cutting structure and intermediate lateral intersections of the second planar subsurface with the cutting structure, the chip breaker feature extending outwardly from the first planar subsurface and the second planar subsurface.
23 . The well construction tool of claim 22 wherein an amount of outward extension of the chip breaker feature is related to a distance away from the lateral intersection of the first planar subsurface and the second planar subsurface on one side of a laterally intermediate point on the chip breaker feature and a distance away from the lateral intersection of the first planar subsurface and the second planar subsurface on an opposed side of the laterally intermediate point.
24 . The well construction tool of claim 23 wherein the intermediate point is mid way between opposed lateral intersections of the first planar subsurface and the second planar subsurface.
25 . The well construction tool of claim 14 further comprising at least one flow channel formed in the cutting structure between the apex and the interface on opposed lateral flanks of the cutting structure, the at least one flow channel having a radius of curvature and depth of cut so as to intersect each lateral flank at less than a full diameter of the cutting structure at a respective longitudinal position along a centerline of the cutting structure.
26 . The well construction tool of claim 25 wherein the at least one flow channel on the opposed lateral flanks subtends an oblique angle with respect to the centerline.
27 . The well construction tool of claim 26 wherein the subtended angle corresponds to an angle subtended between the centerline and an axis of rotation of a tool body to which the cutter is attached.
28 . The well construction tool of claim 25 wherein the shear surface comprises a first planar subsurface intersecting the cutting structure proximate the apex, the first planar subsurface oriented at the larger angle, the shear surface comprising a second planar subsurface intersecting the cutting structure proximate the interface, the second planar subsurface oriented at the smaller angle, the cutter further comprising a chip breaker feature intermediate intersection of the first planar subsurface with the cutting structure and intersection of the second planar subsurface with the cutting structure, the chip breaker feature disposed intermediate lateral intersections of the first planar subsurface with the cutting structure and intermediate lateral intersections of the second planar subsurface with the cutting structure, the chip breaker feature extending outwardly from the first planar subsurface and the second planar subsurface.
29 . The well construction tool of claim 28 wherein an amount of outward extension of the chip breaker feature is related to a distance away from the lateral intersection of the first planar subsurface and the second planar subsurface on one side of a laterally intermediate point on the chip breaker feature and a distance away from the lateral intersection of the first planar subsurface and the second planar subsurface on an opposed side of the intermediate point.
30 . The well construction tool of claim 29 wherein the intermediate point is mid way between opposed lateral intersections of the first planar subsurface and the second planar subsurface.