PRE-RAKED CUTTER ELEMENTS FOR FIXED CUTTER DRILL BITS AND DRILL BITS INCLUDING SAME

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional patent application Ser. No. 63/721,582 filed Nov. 18, 2024, and entitled “Fixed Cutter Drill Bits Including Cutter Elements with Pre-Raked Cutter Elements,” which is hereby incorporated herein by reference in its entirety for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD

The present disclosure relates generally to earth-boring bits used to drill boreholes for the ultimate recovery of oil, gas, or minerals. More particularly, the present disclosure relates to fixed cutter drill bits with cutter elements having raked cutting faces.

BACKGROUND

An earth-boring drill bit is typically mounted on the lower end of a drill string and is rotated by rotating the drill string at the surface or by actuation of downhole motors or turbines, or by both methods. With weight applied to the drill string, the rotating drill bit engages the earthen formation and proceeds to form a borehole along a predetermined path toward a target zone. The borehole thus created has a diameter generally equal to the diameter or “gage” of the drill bit.

Fixed cutter bits, also known as rotary drag bits, are one type of drill bit commonly used to drill boreholes. Fixed cutter bit designs include a plurality of blades angularly spaced about a bit face. The blades generally project radially outward along the bit face and form flow channels therebetween. Cutter elements are typically grouped and mounted on the blades. The configuration or layout of the cutter elements on the blades may vary widely, depending on a number of factors. One of these factors is the formation itself, as different cutter element layouts engage and cut the various strata with differing results and effectiveness.

The cutter elements disposed on the several blades of a fixed cutter bit are typically formed of extremely hard materials and include a layer of polycrystalline diamond (“PCD”) material. In the typical fixed cutter bit, each cutter element includes an elongate and generally cylindrical support member that is received and secured in a pocket formed in the surface of one of the several blades. In addition, each cutter element typically has a hard-cutting layer of polycrystalline diamond or other superabrasive material such as cubic boron nitride, thermally stable diamond, polycrystalline cubic boron nitride, or ultrahard tungsten carbide (meaning a tungsten carbide material having a wear-resistance that is greater than the wear-resistance of the material forming the substrate), as well as mixtures or combinations of these materials. The cutting layer is mounted to one end of the corresponding support member, which is typically formed of tungsten carbide.

While the bit is rotated, drilling fluid is pumped through the drill string and directed out of the face of the drill bit. The fixed cutter bit typically includes nozzles or fixed ports spaced about the bit face that serve to inject drilling fluid into the passageways between the several blades. The drilling fluid exiting the face of the bit through nozzles or ports performs several functions. In particular, the fluid removes formation cuttings (for example, rock chips) from the cutting structure of the drill bit. Otherwise, accumulation of formation cuttings on the cutting structure may reduce or prevent the penetration of the drill bit into the formation. In addition, the fluid removes formation cuttings from the bottom of the hole. Failure to remove formation materials from the bottom of the hole may result in subsequent passes by cutting structure to essentially re-cut the same materials, thereby reducing the effective cutting rate and potentially increasing wear on the cutting surfaces of the cutter elements. The drilling fluid flushes the cuttings removed from the bit face and from the bottom of the hole radially outward and then up the annulus between the drill string and the borehole sidewall to the surface. Still further, the drilling fluid removes heat, caused by contact with the formation, from the cutter elements to prolong cutter element life.

BRIEF SUMMARY

Embodiments of fixed cutter drill bits for drilling earthen formations are disclosed herein. In one embodiment, a fixed cutter drill bit for drilling an earthen formation comprises a bit body having a central axis and a bit face. The bit body is configured to rotate about the central axis in a cutting direction of rotation. The bit face includes a concave cone region extending radially from the central axis, a convex shoulder region extending radially from the cone region, a nose at the intersection of the cone region and the shoulder region, and a gage region extending radially from the shoulder region to a full gage diameter of the drill bit. The drill bit also comprises a cutting structure disposed on the bit face. The cutting structure includes a blade extending radially along the bit face. The blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, a cutter-supporting surface extending from the leading side to the trailing side. In addition, the drill bit comprises a plurality of cutter element assemblies mounted to the cutter-supporting surface of the blade and arranged in a radially extending row proximal the leading side of the blade. Each cutter element assembly comprises a cutter element carrier and a cutter element fixably attached to the cutter element carrier. The cutter element carrier has a central axis, a leading end relative to the cutting direction of rotation, and a trailing end relative to the cutting direction of rotation. The leading end is defined by a sloped planar surface having a surface vector oriented at an acute angle α relative to the central axis of the cutter element carrier. The cutter element has a central axis, a leading end relative to the cutting direction of rotation, and a trailing end relative to the cutting direction of rotation. The cutter element comprises a substrate extending axially from the trailing end and a cutting layer extending axially from the leading end to the substrate. The cutting layer is fixably attached to the substrate. The substrate comprises a planar surface at the trailing end of the cutter element that is oriented perpendicular to the central axis of the cutter element and the cutting layer comprises a cutting face at the leading end of the cutter element. The planar surface at the trailing end of the cutter element engages and is fixably attached to the sloped planar surface of the cutter element carrier.

In another embodiment, a fixed cutter drill bit for drilling an earthen formation comprises a bit body having a central axis and a bit face. The bit body is configured to rotate about the central axis in a cutting direction of rotation. The bit face includes a concave cone region extending radially from the central axis, a convex shoulder region extending radially from the cone region, a nose at the intersection of the cone region and the shoulder region, and a gage region extending radially from the shoulder region to a full gage diameter of the drill bit. The drill bit also comprises a cutting structure disposed on the bit face. The cutting structure includes a blade extending radially along the bit face. The blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, a cutter-supporting surface extending from the leading side to the trailing side. Further, the drill bit comprises a plurality of cutter element assemblies mounted to the cutter-supporting surface of the blade and arranged in a radially extending row proximal the leading side of the blade. Each cutter element assembly comprises a cutter element carrier having a central axis, a leading end relative to the cutting direction of rotation, and a trailing end relative to the cutting direction of rotation. The leading end comprises a planar surface. Each cutter element assembly also comprises a cutter element having a central axis, a leading end relative to the cutting direction of rotation, and a trailing end relative to the cutting direction of rotation. The trailing end of the cutter element is defined by a planar surface oriented perpendicular to the central axis of the cutter element. The cutter element comprises a substrate defining the trailing end of the cutter element and a cutting layer defining a cutting face at the leading end of the cutter element. The cutting layer is fixably coupled to the substrate. The planar surface at the trailing end of the cutter element is positioned flush against and is fixably attached to the planar surface at the leading end of the cutter element carrier. The central axis of the cutter element is oriented at an acute angle β relative to the central axis of the cutter element carrier.

Embodiments described herein comprise a combination of features and characteristics intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical characteristics of the disclosed embodiments in order that the detailed description that follows may be better understood. The various characteristics and features described above, as well as others, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes as the disclosed embodiments. It should also be realized that such equivalent constructions do not depart from the spirit and scope of the principles disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various exemplary embodiments, reference will now be made to the accompanying drawings in which:

FIG. 1 is a schematic view of a drilling system including an embodiment of a drill bit in accordance with the principles described herein;

FIG. 2 is a perspective view of the drill bit of FIG. 1;

FIG. 3 is an end view of the drill bit of FIG. 2;

FIG. 4 is a partial cross-sectional schematic view of the bit shown in FIG. 2 with the blades and the cutting faces of the cutter element assemblies rotated into a single composite profile;

FIG. 5 is a perspective view of one of the cutter element assemblies of the drill bit of FIG. 2;

FIG. 6 is a front side view the cutter element assembly of FIG. 5;

FIG. 7 is a right side view of the cutter element assembly of FIG. 5;

FIG. 8 is a left side view of the cutter element assembly of FIG. 5;

FIG. 9 is a top view of the cutter element assembly of FIG. 5;

FIG. 10 is an end view of an embodiment of a drill bit in accordance with the principles described herein with a plurality of the cutter element assemblies of FIG. 5 mounted to the blades with the cutting faces oriented at forward rake angles.

FIG. 11 is an end view of an embodiment of a drill bit in accordance with the principles described herein with a plurality of the cutter element assemblies of FIG. 5 mounted to the blades with the cutting faces oriented at negative side rake angles;

FIG. 12 is an end view of an embodiment of a drill bit in accordance with the principles described herein with a plurality of the cutter element assemblies of FIG. 5 mounted to the blades with the cutting faces oriented at positive side rake angles;

FIG. 13 is a perspective view an embodiment of a cutter element assembly in accordance with the principles described herein;

FIG. 14 is a top end view of the cutter element assembly of FIG. 13;

FIG. 15 is a front side view the cutter element assembly of FIG. 13;

FIG. 16 is a left side view of the cutter element assembly of FIG. 13;

FIG. 17 is a right side view of the cutter element assembly of FIG. 13; and

FIG. 18 is a rear side of the cutter element assembly of FIG. 13-.

DETAILED DESCRIPTION

The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing FIGS. are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct engagement between the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a particular axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to a particular axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. Any reference to up or down in the description and the claims is made for purposes of clarity, with “up”, “upper”, “upwardly”, “uphole”, or “upstream” meaning toward the surface of the borehole and with “down”, “lower”, “downwardly”, “downhole”, or “downstream” meaning toward the terminal end of the borehole, regardless of the borehole orientation. As used herein, the terms “approximately,” “about,” “substantially,” and the like mean within 10% (i.e., plus or minus 10%) of the recited value. Thus, for example, a recited angle of “about 80 degrees” refers to an angle ranging from 72 degrees to 88 degrees.

Without regard to the type of bit, the cost of drilling a borehole for recovery of hydrocarbons may be very high, and is proportional to the length of time it takes to drill to the desired depth and location. The time required to drill the well, in turn, is greatly affected by the number of times the drill bit must be changed before reaching the targeted formation. This is the case because each time the bit is changed, the entire string of drill pipe, which may be miles long, must be retrieved from the borehole, section by section. Once the drill string has been retrieved and the new bit installed, the bit must be lowered to the bottom of the borehole on the drill string, which again must be constructed section by section. This process, known as a “trip” of the drill string, requires considerable time, effort and expense. Accordingly, it is desirable to employ drill bits which will drill faster and longer. The length of time that a drill bit may be employed before it must be changed depends upon a variety of factors. These factors include the bit's rate of penetration (“ROP”), as well as its durability or ability to maintain a high or acceptable ROP. Other important factors in drilling operations that can have an impact on the length of time to drill to a desired depth and location include the ability of the drill bit to maintain a predetermined or desired drilling trajectory (i.e., bit stability) and the ability to effectively remove formation cuttings away from the drill bit (i.e., bit cleaning) and cool the drill bit during drilling operations (i.e., bit cooling).

One factor that affects bit ROP, durability, bit stability, bit cleaning, and bit cooling is the arrangement and orientation of the cutter elements along the face of the drill bit. For example, the orientation of the cutting face of each cutter element relative to the direction of the cutter element and drill bit, also referred to as the “rake” of the cutting face, can impact performance of the cutter element and associated drill bit. In general, a cutting face can be oriented at a “back rake angle,” “forward rake angle,” “side rake angle” (positive or negative), or combinations thereof. As is known in the art, a cutting face oriented at a “back rake angle” is tilted backward such that the cutting face slopes rearwardly relative to the cutting direction of the cutter element moving radially outward along the cutting face toward the cutting tip distal the cutter-supporting surface of the corresponding blade; a cutting face oriented at a “forward rake angle” is tilted forward such that the cutting face slopes forwardly relative to the cutting direction of the cutter element moving radially outward along cutting face toward the cutting tip distal the cutter-supporting surface of the corresponding blade; a cutting face oriented at a negative “side rake angle” is tilted outwardly and generally away from the bit axis such that a normal vector to the cutting face at the cutting tip distal the cutter-supporting surface of the corresponding blade is angled outwardly away from the central axis of the bit relative to the cutting direction of the cutter element as viewed perpendicular to the cutter-supporting surface of the corresponding blade; and a cutting face oriented at a positive “side rake angle” is tilted inwardly generally toward the central axis of the bit such that a normal vector to the cutting face at the cutting tip distal the cutter-supporting surface of the corresponding blade is angled inwardly toward the central axis of the bit relative to the cutting direction of the cutter element as viewed perpendicular to the cutter-supporting surface of the corresponding blade. Without being limited by this or any particular theory, orienting cutting faces at back rake angles generally reduces the aggressiveness of the cutting faces and associated drill bit (e.g., lower ROP) but enhances the durability of the cutting faces and associated drill bit; orientating cutting faces at forward rake angles generally increases the aggressiveness of the cutting faces and associated drill bit (e.g., higher ROP) but reduces the durability of the cutting faces and associated drill bit; orientating cutting faces at positive side rake angles generally decreases drill bit cleaning and cooling; and orientating cutting faces at negative side rake angles generally increases drill bit cleaning and cooling.

Tailoring and altering the orientation of the cutting faces of conventional cutter elements mounted to a drill bit can be a time consuming and difficult process. This is usually the case as most conventional cutter elements have a cylindrical hard cutting layer defining a cutting face oriented perpendicular to the central axis of the cylindrical substrate to which the hard cutting layers is mounted, and thus, the sockets in the blades of the drill bit that receive the mating substrates must each be formed at the desired rake angle for the corresponding cutting face. Once the bit body is formed, altering the rake angle of any particular cutting face typically requires reforming the corresponding socket in the blade such that it is oriented at the desired rake angle (different than the previous rake angle).

Accordingly, embodiments described herein are directed to cutter element assemblies that can be seated in a given socket of a drill bit in different rotational orientations to alter the rake angle of the corresponding cutting face. Such embodiments enable the rake angles of the cutting faces to be varied as the cutter element assemblies are mounted (or remounted after a period of use) to the blades without the need to alter the orientation of the sockets in which the cutter element assemblies are mounted.

Referring now to FIG. 1, a schematic view of an embodiment of a drilling system 10 in accordance with the principles described herein is shown. Drilling system 10 includes a derrick 11 having a floor 12 supporting a rotary table 14 and a drilling assembly 90 for drilling a borehole 26 from derrick 11. Rotary table 14 is rotated by a prime mover such as an electric motor (not shown) at a desired rotational speed and controlled by a motor controller (not shown). In other embodiments, the rotary table (for example, rotary table 14) may be augmented or replaced by a top drive suspended in the derrick (for example, derrick 11) and connected to the drillstring (for example, drillstring 20).

Drilling assembly 90 includes a drillstring 20 and a drill bit 100 coupled to the lower end of drillstring 20. Drillstring 20 is made of a plurality of pipe joints 22 connected end-to-end, and extends downward from the rotary table 14 through a pressure control device 15, such as a blowout preventer (BOP), into the borehole 26. The pressure control device 15 is commonly hydraulically powered and may contain sensors for detecting certain operating parameters and controlling the actuation of the pressure control device 15. Drill bit 100 is rotated with weight-on-bit (WOB) applied to drill the borehole 26 through the earthen formation. Drillstring 20 is coupled to a drawworks 30 via a kelly joint 21, swivel 28, and line 29 through a pulley. During drilling operations, drawworks 30 is operated to control the WOB, which impacts the rate-of-penetration of drill bit 100 through the formation. In this embodiment, drill bit 100 can be rotated from the surface by drillstring 20 via rotary table 14 or a top drive, rotated by downhole mud motor 55 disposed along drillstring 20 proximal bit 100, or combinations thereof (for example, rotated by both rotary table 14 via drillstring 20 and mud motor 55, rotated by a top drive and the mud motor 55, etc.). For example, rotation via downhole motor 55 may be employed to supplement the rotational power of rotary table 14, if required, or to effect changes in the drilling process. In either case, the rate-of-penetration (ROP) of the drill bit 100 into the borehole 26 for a given formation and a drilling assembly largely depends upon the WOB and the rotational speed of bit 100.

During drilling operations, a suitable drilling fluid 31 is pumped under pressure from a mud tank 32 through the drillstring 20 by a mud pump 34. Drilling fluid 31 passes from the mud pump 34 into the drillstring 20 via a desurger 36, fluid line 38, and the kelly joint 21. The drilling fluid 31 pumped down drillstring 20 flows through mud motor 55 and is discharged at the borehole bottom through nozzles in face of drill bit 100, circulates to the surface through an annular space 27 radially positioned between drillstring 20 and the sidewall of borehole 26, and then returns to mud tank 32 via a solids control system 36 and a return line 35. Solids control system 36 may include any suitable solids control equipment known in the art including, without limitation, shale shakers, centrifuges, and automated chemical additive systems. Control system 36 may include sensors and automated controls for monitoring and controlling, respectively, various operating parameters such as centrifuge rpm. It should be appreciated that much of the surface equipment for handling the drilling fluid is application specific and may vary on a case-by-case basis.

Referring now to FIGS. 2 and 3, drill bit 100 is a fixed cutter bit, sometimes referred to as a drag bit, and is designed for drilling through formations of rock to form a borehole. Bit 100 has a central or longitudinal axis 105, a first or uphole end 100a, and a second or downhole end 100b. Bit 100 rotates about axis 105 in the cutting direction represented by arrow 106. In addition, bit 100 includes a bit body 110 extending axially from downhole end 100b, a threaded connection or pin 120 extending axially from uphole end 100a, and a shank 130 extending axially between pin 120 and body 110. Pin 120 couples bit 100 to a drill string (not shown), which is employed to rotate the bit 100 in order to drill the borehole. Bit body 110, shank 130, and pin 120 are coaxially aligned with axis 105, and thus, each has a central axis coincident with axis 105.

The portion of bit body 110 that faces the formation at downhole end 100b includes a bit face 111 provided with a cutting structure 140. Cutting structure 140 includes a plurality of blades that extend from bit face 111. As best shown in FIG. 3, in this embodiment, cutting structure 140 includes three angularly spaced-apart primary blades 141 and two angularly spaced apart secondary blades 142. Further, in this embodiment, the plurality of blades (for example, primary blades 141, and secondary blades 142) are uniformly angularly spaced on bit face 111 about bit axis 105. In particular, the three primary blades 141 and the two secondary blades 142 (a total of five blades 141, 142) are uniformly angularly spaced about 72° apart. In other embodiments, one or more of the blades may be spaced non-uniformly about bit face 111. Still further, in this embodiment, each secondary blade 142 is disposed between a pair of circumferentially-adjacent primary blades 141. Although bit 100 is shown as having three primary blades 141 and two secondary blades 142, in general, bit 100 may comprise any suitable number of primary and secondary blades. As one example only, bit 100 may comprise two primary blades and four secondary blades, or three primary blades and three secondary blades.

Referring again to FIGS. 2 and 3, in this embodiment, primary blades 141 and secondary blades 142 are integrally formed as part of, and extend from, bit body 110 and bit face 111. Primary blades 141 and secondary blades 142 extend generally radially along bit face 111 and then axially along a portion of the periphery of bit 100. In particular, primary blades 141 extend radially from proximal central axis 105 toward the periphery of bit body 110. Primary blades 141 and secondary blades 142 are separated by drilling fluid flow courses 143. Each blade 141, 142 has a leading edge or side 141a, 142a, respectively, and a trailing edge or side 141b, 142b, respectively, relative to the cutting direction of rotation 106 of bit 100.

Each blade 141, 142 includes a cutter-supporting surface 144 that generally faces the formation during drilling and extends circumferentially from the leading side 141a to the trailing side 142 of the corresponding blade 141, 142. In this embodiment, a plurality of cutter element assemblies 200 are fixably attached to each blade 141, 142 and extend from cutter-supporting surface 144 of each blade 141, 142. In particular, each cutter element assembly 200 is received and seated in a mating recess or socket 145 extending circumferentially from the leading side 141a, 142b and cutter supporting surface 144 into the corresponding blade 141, 142. Cutter element assemblies 200 are generally arranged adjacent one another in a radially extending row proximal the leading side 141a, 142a of each blade 141, 142, respectively. However, in other embodiments, the cutter element assemblies (for example, cutter element assemblies 200) may be arranged differently.

As will be described in more detail below, each cutter element assembly 200 includes a carrier 210 fixably mounted to the corresponding blade 141, 142 (e.g., via brazing) in mating socket 145 and a cutter element 230 fixably secured to carrier 210 (e.g., via brazing). Each cutter element 230 includes a support base or substrate 231 and a disk or tablet-shaped, hard cutting layer 232 fixably secured or bonded to the exposed end of substrate 231. Each cutter element 230 is mounted flush to one end of the corresponding carrier 210, which in turn is fixably received by and secured in the corresponding socket 145 of the corresponding blade 141, 142 to which cutter element assembly 200 is mounted. Each carrier 210 is made of a carbide material such as tungsten carbide. In addition, substrate 231 is made of a carbide material such as tungsten carbide, whereas cutting layer 232 is made of polycrystalline diamond or other superabrasive material.

In this embodiment, carrier 210 is cylindrical and cutter element 230 is cylindrical (i.e., substrate 231 and cutting layer 232 are cylindrical). Consequently, each socket 145 is cylindrical to receive the mating cutter element assembly 200, and in particular to receive the mating carrier 210. However, in other embodiments, the carrier (e.g., carrier 210) and/or the cutter element mounted thereto (e.g., cutter element 230) may have other geometries (e.g., rectangular prismatic, octagonal prismatic, oval prismatic, etc.). In general, the socket (e.g., socket 145) that receives the cutter element assembly (e.g., cutter element assembly 200) has a geometry that mates with the cutter element assembly, and in particular, the cutter element carrier.

The cylindrical disc, hard cutting layer 232 defines a cutting face 233 of the corresponding cutter element 230. In this embodiment, each cutting face 233 is the same and is planar. However, in other embodiments, one or more cutting faces (e.g., cutting faces 233) may not be completely planar, but rather, be non-planar. As used herein, the phrase “non-planar” may be used to refer to a cutting face that includes one or more curved surfaces (for example, concave surface(s), convex surface(s), or combinations thereof), a plurality of distinct planar surfaces that intersect at distinct edges along the cutting face, or combinations thereof. The portion of cutting face 233 of each cutter element 230 positioned furthest from the cutter-supporting surface 144 of the corresponding blade 141, 142 as measured perpendicular to the corresponding cutter-supporting surface 144 defines a cutting tip 234 of cutting face 233. Each cutter element assembly 200 and each cutter element 230 has an exposure or extension height measured perpendicularly from cutter-supporting surface 144 of the corresponding blade 141, 142 to the corresponding cutting tip 234.

As will be described in more detail below, each carrier 210 has a central axis 215 and each substrate 231 has a central axis 235 that defines the central axis of the corresponding cutter element 230. In the embodiments described herein, each cutter element assembly 200 is mounted to a corresponding blade 141, 142 such that the central axis 235 of the corresponding cutter element 230 is oriented substantially parallel to or at an acute angle relative to the cutting direction of the bit (for example, cutting direction 106 of bit 100). Such orientation results in the corresponding cutting face 233 being generally forward-facing relative to the cutting direction of the bit (for example, cutting direction 106 of bit 100). With cutting faces 233 oriented in such forward-facing manner, cuttings tip 234 and portions of cutting faces 233 circumferentially and radially adjacent to the corresponding cutting tips 234 (relative to central axes 235) are designed and configured to engage and shear the subterranean formation during drilling operations.

Referring again to FIGS. 2 and 3, bit body 110 further includes gage pads 147 of substantially equal axial length measured generally parallel to bit axis 105. Gage pads 147 are circumferentially-spaced about the radially outer surface of bit body 110. Specifically, one gage pad 147 intersects and extends from each blade 141, 142. In this embodiment, gage pads 147 are integrally formed as part of the bit body 110. In general, gage pads 147 can help maintain the size of the borehole by a rubbing action when cutter element assemblies 200 wear slightly under gage. Gage pads 147 also help stabilize bit 100 against vibration.

Referring now to FIG. 4, an exemplary profile of blades 141, 142 (right side of FIG. 4) and an exemplary profile of cutting faces 233 (left side of FIG. 4) are shown as each would appear with blades 141, 142 and cutting faces 233 rotated into a single rotated profile. In rotated profile view, blades 141, 142 form a combined or composite blade profile 148a generally defined by cutter-supporting surfaces 144 of blades 141, 142, and cutting tips 234 of cutting faces 233 form a combined or composite cutting face profile 148b generally defined by a line passing through cutting tips 234 of cutting faces 233 mounted to blades 141, 142. In this embodiment, the profiles of surfaces 144 of blades 141, 142 are generally coincident with each other, thereby forming a single composite blade profile 148a; and cutting tips 234 on different blades 141, 142 are generally disposed along the generally smooth and continuous cutting profile 148b. As shown in FIG. 4, profiles 148a, 148b have a similar shape and are generally parallel to each other when rotated into a single profile.

Composite blade profile 148a and bit face 111 may generally be divided into three regions conventionally labeled cone region 149a, shoulder region 149b, and gage region 149c. Cone region 149a is the radially innermost region of bit body 110 and composite blade profile 148a that extends from bit axis 105 to shoulder region 149b. In this embodiment, cone region 149a is generally concave. Adjacent cone region 149a is generally convex shoulder region 149b. The transition between cone region 149a and shoulder region 149b, referred herein to as the nose 149d, occurs at the axially outermost portion of composite blade profile 148a (relative to bit axis 105) where a tangent line to the blade profile 148a has a slope of zero. Moving radially outward, adjacent shoulder region 149b is the gage region 149c, which extends substantially parallel to bit axis 105 at the outer radial periphery of composite blade profile 148a. As shown in composite blade profile 148a, gage pads 147 generally define the gage region 149c and the outer radius R₁₁₀ of bit body 110. Outer radius R₁₁₀ extends to and therefore defines the full gage diameter of bit 100.

Referring briefly to FIGS. 3 and 4, moving radially outward from bit axis 105, bit 100 and bit face 111 include cone region 149a, shoulder region 149b, and gage region 149c as previously described. Primary blades 141 extend radially along bit face 111 from within cone region 149a proximal bit axis 105 toward gage region 149c and outer radius R₁₁₀. Secondary blades 142 extend radially along bit face 111 from cone region 149a proximal nose 149d toward gage region 149c and outer radius R₁₁₀. Thus, in this embodiment, each primary blade 141 and each secondary blade 142 extends substantially to gage region 149c and outer radius R₁₁₀. In this embodiment, secondary blades 142 extend radially inward just inside cone region 149a proximal nose 149d, and thus, secondary blades 142 occupy very little space on bit face 111 within cone region 149a. Although a specific embodiment of bit body 110 has been shown in described, one skilled in the art will appreciate that numerous variations in the size, orientation, and locations of the blades (for example, primary blades 141, secondary blades 142, etc.), cutter element assemblies (for example, cutter element assemblies 200), and cutter elements (e.g., cutter elements 230′) are possible.

Bit 100 includes an internal plenum extending axially from uphole end 100a through pin 120 and shank 130 into bit body 110. The plenum allows drilling fluid to flow from the drill string into bit 100. Body 110 is also provided with a plurality of flow passages extending from the plenum to downhole end 100b. As best shown in FIGS. 2 and 3, a nozzle 108 is seated in the lower end of each flow passage. Together, the plenum, passages, and nozzles 108 serve to distribute drilling fluid around cutting structure 140 to flush away formation cuttings and to remove heat from cutting structure 140, and more particularly cutter element assemblies 200 during drilling.

Referring briefly to FIGS. 2-4, on each blade 141, 142, cutter element assemblies 200 are arranged side-by-side in a row along the corresponding cutter-supporting surface 144 proximal leading side 141a, 142a. Thus, in this embodiment, cutter element assemblies 200 are positioned radially adjacent one another (relative to bit axis 105) on a given blade 141, 142. However, in other embodiments, the cutter elements (for example, cutter element assemblies 200) may be arranged in rows with one or more cutter element having different geometries on the same blade (for example, blade 141, 142).

Referring now to FIGS. 5-9, one cutter element assembly 200 will be described, it being understood the other cutter element assemblies 200 are the same. As previously described, cutter element assembly 200 includes cutter element carrier 210 and cutter element 230 fixably mounted to carrier 210. In particular, carrier 210 has central axis 215, a first end 210a, a second end 210b opposite end 210a, and a radially outer surface 211 extending axially from first end 210a to second end 210b. When cutter element assembly 200 is mounted to a corresponding blade 141, 142 of bit 100, second end 210b generally leads first end 210a relative to cutting direction 106 of bit 100, and thus, second end 210b may also be referred to as “leading” end 210b and first end 210a may also be referred to as “trailing” end 210a. In this embodiment, first end 210a is defined by a planar surface 212 oriented perpendicular to central axis 215 and second end 210b is defined by a planar surface 213 oriented at an acute angle relative to central axis 215. Thus, planar surfaces 212, 213 are not oriented parallel to each other. More specifically, as best shown in right and left side views of FIGS. 7 and 8, planar surface 213 has a surface or normal vector V₂₁₃ (oriented perpendicular to surface 213) that is oriented at an acute angle α relative to central axis 215. In embodiments described herein, the angle α ranges from 2° to 40°, alternatively ranges from 4° to 30°, and alternatively ranges from 5° to 20°.

Due to the slope of planar surface 213, carrier 210 may be described as having a peak 216 along sloped planar surface 212 adjacent outer surface 211 and a bottom 217 along sloped planar surface 212 adjacent outer surface 211. Peak 216 is radially opposed bottom 217. In other words, peak 216 and bottom 217 are angularly spaced 180° apart about axis 215. As best shown in FIG. 7, carrier 210 has a height or length L₂₁₀ measured axially from planar surface 212 at trailing end 210a to planar surface 213 at leading end 210b. The length L₂₁₀ of carrier 210 is a maximum at peak 216 and a minimum at bottom 217.

In this embodiment, outer surface 211 is a cylindrical surface extending between ends 210a, 210b. In addition, in this embodiment, an annular bevel or chamfer 214 is positioned at the intersection of outer surface 211 and planar surface 212. As best shown in FIGS. 6 and 8, carrier 210 has a diameter D₂₁₀ measured perpendicular to central axis 215.

As best shown in the front, right side, and left side views of FIGS. 6-8, in this embodiment, outer surface 211 is marked or stamped with four uniformly circumferentially-spaced identifiers “B” (in the front view of FIG. 6), “+ S +” (in the right side view of FIG. 7), “− S −” (in the left side view of FIG. 8), and “F” (in the rear view, which is not visible but is radially opposite identifier “B”). Thus, the identifiers are angularly spaced 90° apart about outer surface 211. As will be described in more detail below, the identifiers can be used during assembly of bit 100 to orient any given cutter element assembly 200 at a pre-determined back rake (identifier “B”), forward rake (identifier “F”), positive side rake (identifier “+ S +”), or negative side rake (identifier “− S −”).

As previously described, cutter element 230 includes cylindrical substrate 231 and cylindrical hard cutting layer 232 fixably bonded to substrate 231. More specifically, cutter element 230 has a first end 230a, a second end 230b opposite end 230a, and a radially outer surface 236 extending axially from first end 230a to second end 230b. When cutter element assembly 200 is mounted to a corresponding blade 141, 142 of bit 100, second end 230b generally leads first end 230a relative to cutting direction 106 of bit 100, and thus, second end 230b may also be referred to as leading end 230b and first end 230a may also be referred to as trailing end 230a.

Substrate 231 has central axis 235, which defines the central axis of cutter element 230, and extends axially (relative to axis 235) from first end 230a to cutting layer 232. Cutting layer 232 extends axially (relative to axis 235) from second end 230b to substrate 231. First end 230a is defined by a planar surface 237 and second end 232b is defined by cutting face 233. Planar surface 237 is oriented perpendicular to axis 235. In this embodiment, cutting face 233 is defined by a planar surface oriented perpendicular to axis 235. Thus, in this embodiment, cutting face 233 and planar surface 237 are oriented parallel to each other. In other embodiments, the cutting face (e.g., cutting face 233) may be non-planar as previously described and/or the cutting face may not be oriented parallel to planar surface 237.

In this embodiment, outer surface 236 is a cylindrical surface oriented parallel to axis 235 and extending axially (relative to axis 235) between ends 230a, 230b. Thus, substrate 231 and cutting layer 232 have contiguous radially outer cylindrical surfaces. In addition, in this embodiment, an annular bevel or chamfer 238 is provided at the intersection of planar surface 237 and outer surface 236, and an annular bevel or chamfer 239 is provided at the intersection of cutting face 233 and outer surface 236. As best shown in FIGS. 6 and 8, cutter element 230 has an outer diameter D₂₃₀ measured perpendicular to axis 235. In this embodiment, the outer diameter D₂₃₀ of cutter element 230 is the same as the outer diameter D₂₁₀ of carrier 210. However, in other embodiments, the outer diameter of the cutter element (e.g., outer diameter D₂₃₀ of cutter element 230) may be different than the outer diameter of the carrier (e.g., the outer diameter D₂₁₀ of carrier 210).

Referring again to FIGS. 5-9, cutter element 230 is fixably secured to carrier 210. In particular, planar surface 237 at end 230a of cutter element 230 is positioned flush against planar surface 212 at end 210b of carrier 210 and attached thereto. In this embodiment, cutter element 230 is attached to carrier 210 with a braze alloy (e.g., a high temperature braze). In other embodiments, different types of brazing or other attachment techniques may be used to secure the cutter element (e.g., cutter element 230) to the carrier (e.g., carrier 210).

As best shown in FIGS. 7 and 8, in this embodiment, the diameter D₂₃₀ of cutter element 230 is the same as the diameter D₂₁₀ of carrier 210, however, due to planar surface 213 being sloped, cutter element 230 does not extend completely across planar surface 213. In this embodiment, cutter element 230 engages and extends across planar surface 213 from peak 216 toward but not completely to bottom 217. Thus, radially outer surface 236 of cutter element 230 is radially and axially adjacent (relative to axes 215, 235) radially outer surface 211 of carrier 210 at peak 216 but is radially spaced (relative to axes 215, 235) from radially outer surface 211 of carrier 210 at bottom 217. Radially outer surface 236 of cutter element 230 is oriented parallel to axis 235 and perpendicular to surface 237, and thus, radially outer surface 236 generally slopes toward axis 215 of carrier 210 moving axially (relative to axis 235) from surface 213 at peak 216 and generally slopes away from axis 215 of carrier moving axially (relative to axis 2235) from surface 213 proximal bottom 217.

As best shown in the right and left side views of FIGS. 7 and 8, due to cylindrical cutter element 230 being secured to sloped planar surface 213 at leading end 210b of carrier 210, axes 215, 235 are oriented at an acute angle β relative to each other. As surfaces 233, 237 at ends 230b, 230a, respectively, of cutter element 230 are oriented parallel to each other in this embodiment, angle β is the same as angle α. For a given position and orientation of a socket 145, angles α, β and the rotational orientation of cutter element assembly 200 generally define the rake angle of cutter element assembly 200 when it is secured to a corresponding blade 141, 142 in the mating socket 145. Angles α, β are fixed and defined during manufacture of cutter element assembly 200 (i.e., angles α, β are generally pre-determined before cutter element assembly 200 is secured to the corresponding blade 141, 142). Thus, by adjusting the rotational orientation of a cutter element assembly 200 (about axis 215 and the coaxially aligned central axis of mating socket 145) upon securing such cutter element assembly 200 to a corresponding blade 141, 142 in a mating socket 145, the rake angle of the cutting face 233 of the cutter element assembly 200 can be varied. For example, referring again to FIG. 3, cutter element assemblies 200 are mounted to bit and rotationally oriented within corresponding sockets 145 such that each cutting face 233 is oriented at a back rake angle (i.e., each cutting face 233 is tilted backward such that the cutting face 233 slopes rearwardly relative to the cutting direction 106 moving radially relative to axis 235 along the cutting face 233 toward the corresponding cutting tip 234).

To aid in orienting cutter element assemblies 200 during assembly of bit 100 such that each cutting face 233 is oriented at a back rake angle, identifier “B” is circumferentially positioned on outer surface 211 of carrier 210 such that it faces away from cutter-supporting surface 144 of the corresponding blade 141, 142 when the corresponding cutting face 233 is disposed at the back rake angle. Thus, prior to brazing any given cutter element assembly 200 to a blade 141, 142 within the corresponding socket 145, the technician building bit 100 can rotate the cutter element assembly 200 such that identifier “B” faces away from the corresponding cutter-supporting surface 144 to ensure the corresponding cutting face 233 is oriented at the back rake angle.

As previously described, in the embodiment of drill bit 100 shown in FIGS. 2 and 3, each cutter element assembly 200 is rotationally oriented such that each cutting face 233 is disposed at a back rake angle. However, in other embodiments, any one or more cutter element assemblies 200 can be rotationally oriented such that any one or more cutting faces 233 is/are disposed at a back rake angle, a positive side rake angle, a negative side rake angle, or a forward rake angle. For example, referring now to FIG. 10, an embodiment of a drill bit 300 in accordance with principles described herein is shown. Drill bit 300 is the same as drill bit 100 previously described with the sole exception that each cutter element assembly 200 is rotationally oriented such that that each cutting face 233 is disposed at a forward rake angle (i.e., each cutting face 233 is tilted forward such that the cutting face 233 slopes forwardly relative to the cutting direction 106 of the corresponding cutter element assembly 200 moving radially outward along the cutting face 233 toward the cutting tip 234 distal cutter-supporting surface 144 of the corresponding blade 141, 142). To aid in orienting cutter element assemblies 200 during assembly of bit 300 such that each cutting face 233 is oriented at a forward rake angle, identifier “F” is circumferentially positioned on outer surface 211 of carrier 210 such that it faces away from cutter-supporting surface 144 of the corresponding blade 141, 142 when the corresponding cutting face 233 is disposed at the forward rake angle. Thus, prior to brazing any given cutter element assembly 200 to a blade 141, 142 within the corresponding socket 145, the technician building bit 300 can rotate the cutter element assembly 200 such that identifier “F” faces away from the corresponding cutter-supporting surface 144 to ensure the corresponding cutting face 233 is oriented at the forward rake angle.

As another example, referring now to FIG. 11, an embodiment of a drill bit 400 in accordance with principles described herein is shown. Drill bit 400 is the same as drill bit 100 previously described with the sole exception that each cutter element assembly 200 is rotationally oriented such that that each cutting face 233 is disposed at a negative side rake angle (i.e., each cutting face 233 is tilted outwardly and generally away from bit axis 105 such that a normal vector to the cutting face 233 at cutting tip 234 is angled outwardly away from central axis 105 relative to the cutting direction 106 of the cutter element assembly 200 as viewed perpendicular to the cutter-supporting surface 144 of the corresponding blade 141, 142). To aid in orienting cutter element assemblies 200 during assembly of bit 400 such that each cutting face 233 is oriented at a negative side rake angle, identifier “− S −” is circumferentially positioned on outer surface 211 of carrier 210 such that it faces away from cutter-supporting surface 144 of the corresponding blade 141, 142 when the corresponding cutting face 233 is disposed at the negative side rake angle. Thus, prior to brazing any given cutter element assembly 200 to a blade 141, 142 within the corresponding socket 145, the technician building bit 400 can rotate the cutter element assembly 200 such that identifier “− S −” faces away from the corresponding cutter-supporting surface 144 to ensure the corresponding cutting face 233 is oriented at the negative side rake angle.

As yet another example, referring now to FIG. 12, an embodiment of a drill bit 500 in accordance with principles described herein is shown. Drill bit 500 is the same as drill bit 100 previously described with the sole exception that each cutter element assembly 200 is rotationally oriented such that that each cutting face 233 is disposed at a positive side rake angle (i.e., each cutting face 233 is tilted inwardly and generally toward from bit axis 105 such that a normal vector to the cutting face 233 at cutting tip 234 is angled inwardly toward central axis 105 relative to the cutting direction 106 of the cutter element assembly 200 as viewed perpendicular to the cutter-supporting surface 144 of the corresponding blade 141, 142). To aid in orienting cutter element assemblies 200 during assembly of bit 500 such that each cutting face 233 is oriented at a positive side rake angle, identifier “+ S +” is circumferentially positioned on outer surface 211 of carrier 210 such that it faces away from cutter-supporting surface 144 of the corresponding blade 141, 142 when the corresponding cutting face 233 is disposed at the positive side rake angle. Thus, prior to brazing any given cutter element assembly 200 to a blade 141, 142 within the corresponding socket 145, the technician building bit 500 can rotate the cutter element assembly 200 such that identifier “+ S +” faces away from the corresponding cutter-supporting surface 144 to ensure the corresponding cutting face 233 is oriented at the positive side rake angle.

As previously described, in the embodiment of drill bit 100 shown in FIGS. 2 and 3, each cutter element assembly 200 is rotationally oriented such that each cutting face 233 is disposed at a back rake angle; in the embodiment of a drill bit 300 shown in FIG. 10, each cutter element assembly 200 is rotationally oriented such that each cutting face 233 is disposed at a forward rake angle; in the embodiment of a drill bit 400 shown in FIG. 11, each cutter element assembly 200 is rotationally oriented such that each cutting face 233 is disposed at a negative side rake angle; and in the embodiment of a drill bit 500 shown in FIG. 12, each cutter element assembly 200 is rotationally oriented such that each cutting face 233 is disposed at a positive side rake angle. However, in other embodiments, each cutter element assembly 200 does not need to be rotationally oriented such that each cutting face 233 is disposed at the same rake angle (e.g., back rack angle, forward rake angle, positive side rake angle, or negative side rake angle). For example, in other embodiments, a single fixed cutter drill bit may include one or more cutter element assemblies 200 rotationally oriented such that the corresponding cutting face(s) 233 is/are oriented at a back rake angle, a forward rake angle, a negative side rake angle, a positive side rake angle, or combinations thereof. Moreover, any one or more such cutter element assemblies 200 can be positioned along the cone region (e.g., cone region 149a), the shoulder region (e.g., shoulder region 149b), the gage region (e.g., gage region 149c), or combinations thereof.

In the embodiment of cutter element assembly 200 previously described, cutting face 233 is completely planar. However, in other embodiments, one or more cutting faces (e.g., cutting faces 233) may not be completely planar, but rather, be non-planar. For example, referring now to FIGS. 13-18, an embodiment of a cutter element assembly 600 that can be used in place of one or more cutter element assemblies 200 in bit 100 previously described is shown. Cutter element assembly 600 is substantially the same as cutter element assembly 200 with the exception that cutter element assembly 600 includes a non-planar cutting face 633. Thus, in this embodiment, cutter element assembly 600 includes a carrier 210 fixably configured to be mounted to a corresponding blade 141, 142 (e.g., via brazing) in a mating socket 145 and a cutter element 630 fixably secured to carrier 210 (e.g., via brazing). Carrier 210 is as previously described. Cutter element 630 is substantially the same as cutting element 230 previously described. More specifically, cutter element 630 includes a cylindrical substrate 231 as previously described and a cylindrical hard cutting layer 632 fixably bonded to substrate 231. Carrier 210 and substrate 231 are made of carbide materials such as tungsten carbide, whereas cutting layer 632 is made of polycrystalline diamond or other superabrasive material.

Cutter element 630 has a first or trailing end 630a, a second or leading end 630b opposite end 630a, and a radially outer surface 636 extending axially from first end 630a to second end 630b. Cutting layer 632 extends axially from second end 630b to substrate 231. Trailing end 630a is defined by a planar surface 637 and second end 632b is defined by a cutting face 633. Planar surface 637 is oriented perpendicular to axis 235. In this embodiment, cutting face 633 is defined by a non-planar surface. Thus, in this embodiment, cutting face 633 and planar surface 637 are not oriented parallel to each other.

In this embodiment, outer surface 636 is a cylindrical surface oriented parallel to axis 235 and extending axially between ends 630a, 630b. Thus, substrate 231 and cutting layer 632 have contiguous radially outer cylindrical surfaces. In addition, in this embodiment, an annular bevel or chamfer 638 is provided at the intersection of planar surface 637 and outer surface 636, and an annular bevel or chamfer 639 is provided at the intersection of cutting face 633 and outer surface 636. Cutter element 630 has an outer diameter D₆₃₀ measured perpendicular to axis 235. In this embodiment, the outer diameter D₆₃₀ of cutter element 630 is the same as the outer diameter D₂₁₀ of carrier 210. However, in other embodiments, the outer diameter of the cutter element (e.g., outer diameter D₆₃₀ of cutter element 630) may be different than the outer diameter of the carrier (e.g., the outer diameter D₂₁₀ of carrier 210). In general, cutter element assembly 600 is mounted to a blade 141, 142 in the same manner as cutter element assembly 200 previously described, and cutter element assembly 600 can be rotated to achieve different rake angles (e.g., a back rake angle, a forward rake angle, a positive side rake angle, or a negative side rake angle).

In the manner described, a single cutter element assembly (e.g., cutter element assembly 200) can be seated in a mating socket (e.g., socket 145) in a blade of a drill bit (e.g., blade 141, 142) at different rotational positions to orient the cutting face of the cutter element assembly (e.g., cutting face 233) at a back rake angle, a forward rake angle, a negative side rake angle, or a positive side rake angle. The rake angle of each cutter element assembly can be adjusted as desired during assembly of the drill bit or during maintenance of the drill bit such as for example when the cutter element assemblies are refurbished or replaced during drilling operations.

While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.