Fixed cutter drill bits including cutter elements with high abrasion resistant polycrystalline diamond segments

Abstract

A cutter element for a fixed cutter drill bit configured to drill a borehole in a subterranean formation has a central axis, a leading end defining a cutting face, and a trailing end opposite the leading end. The cutter element includes a chassis having a central axis coaxially aligned with the central axis of the cutter element, a first end at the leading end of the cutter element, a second end at the trailing end of the cutter element, and a radially outer surface extending axially from the first end to the second end. The chassis includes a pocket extending axially from the cutting face at the first end of the chassis, wherein the pocket intersects the radially outer surface of the chassis. The cutter element also includes a pre-manufactured polycrystalline diamond (PCD) segment having a composition consisting essentially of PCD. The PCD segment is disposed in the pocket and fixably secured to the chassis. The PCD segment is disposed at the leading end of the cutter element and is configured to engage the formation during drilling.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. provisional patent application Ser. No. 63 / 762,150 filed Feb. 24, 2025, and entitled “Fixed Cutter Drill Bits Including Cutter Elements with High Abrasion Resistant Polycrystalline Diamond Segments,” which is hereby incorporated herein by reference in its entirety for all purposes.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.FIELD

[0003] The present disclosure relates generally to earth-boring bits used to drill a borehole for the ultimate recovery of oil, gas or minerals. More particularly, the present disclosure relates to cutter elements for fixed cutter drill bits that have improved wear resistance.BACKGROUND

[0004] 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.

[0005] 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.

[0006] 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 carbide.

[0007] 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

[0008] Embodiments of cutter elements for fixed cutter drill bits configured to drill boreholes in subterranean formations are disclosed herein. In one embodiment, a cutter element for a fixed cutter drill bit has a central axis, a leading end defining a cutting face, and a trailing end opposite the leading end. The cutter element comprises a chassis having a central axis coaxially aligned with the central axis of the cutter element, a first end at the leading end of the cutter element, a second end at the trailing end of the cutter element, and a radially outer surface extending axially from the first end to the second end. The chassis includes a pocket extending axially from the cutting face at the first end of the chassis, wherein the pocket intersects the radially outer surface of the chassis. The cutter element also comprises a pre-manufactured polycrystalline diamond (PCD) segment having a composition consisting essentially of PCD. The PCD segment is disposed in the pocket and fixably secured to the chassis. The PCD segment is disposed at the leading end of the cutter element and is configured to engage the formation during drilling.

[0009] In another embodiment, a cutter element for a fixed cutter drill bit has a central axis, a leading end defining a cutting face, and a trailing end opposite the leading end. The cutter element comprises a chassis having a central axis coaxially aligned with the central axis of the cutter element, a first end at the leading end of the cutter element, a second end at the trailing end of the cutter element, and a radially outer cylindrical surface extending axially from the first end to the second end. The cutter element also comprises a pre-manufactured polycrystalline diamond (PCD) segment having a composition consisting essentially of PCD. The PCD segment is fixably secured in a pocket in the cutting face of the cutter element. The first end of the chassis defines a portion of the cutting face of the cutter element and the PCD segment defines a portion of the cutting face at the leading end of the cutter element.

[0010] 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

[0011] For a detailed description of various exemplary embodiments, reference will now be made to the accompanying drawings in which:

[0012] FIG. 1 is a schematic view of a drilling system including an embodiment of a drill bit in accordance with the principles described herein;

[0013] FIG. 2 is a perspective view of the drill bit of FIG. 1;

[0014] FIG. 3 is an end view of the drill bit of FIG. 2;

[0015] 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 elements rotated into a single composite profile;

[0016] FIG. 5 is a perspective view of one of the cutter elements of drill bit of FIG. 2;

[0017] FIG. 6 is a side view of the cutter element of FIG. 5;

[0018] FIG. 7 is a top end view of the cutter element of FIG. 5;

[0019] FIG. 8 is a perspective view of an embodiment of a cutter element in accordance with the principles described herein;

[0020] FIG. 9 is a side view of the cutter element of FIG. 8;

[0021] FIG. 10 is a top end view of the cutter element of FIG. 8;

[0022] FIG. 11 is a perspective view of an embodiment of a cutter element in accordance with the principles described herein;

[0023] FIG. 12 is a side view of the cutter element of FIG. 11;

[0024] FIG. 13 is a top end view of the cutter element of FIG. 11;

[0025] FIG. 14 is a perspective view of an embodiment of a cutter element in accordance with the principles described herein;

[0026] FIG. 15 is a side view of the cutter element of FIG. 14;

[0027] FIG. 16 is a top end view of the cutter element of FIG. 14;

[0028] FIG. 17 is a perspective view of an embodiment of a cutter element in accordance with the principles described herein;

[0029] FIG. 18 is a side view of the cutter element of FIG. 17;

[0030] FIG. 19 is a top end view of the cutter element of FIG. 17;

[0031] FIG. 20 is a perspective view of an embodiment of a cutter element in accordance with the principles described herein;

[0032] FIG. 21 is a side view of the cutter element of FIG. 20;

[0033] FIG. 22 is a top end view of the cutter element of FIG. 20;

[0034] FIG. 23 is a perspective view of an embodiment of a cutter element in accordance with the principles described herein;

[0035] FIG. 24 is a side view of the cutter element of FIG. 23; and

[0036] FIG. 25 is a top end view of the cutter element of FIG. 23.DETAILED DESCRIPTION

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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. . . . ” As used herein, the phrases “consist(s) of” and “consisting of” are used to refer to exclusive components of a composition, meaning only those expressly recited components are included in the composition; whereas the phrases “consist(s) essentially of” and “consisting essentially of” are used to refer to the primary components of a composition, meaning that only small or trace amounts of components other than the expressly recited components (e.g., impurities, byproducts, etc.) may be included in the composition. For example, a composition consisting of X and Y refers to a composition that only includes X and Y, and thus, does not include any other components; and a composition consisting essentially of X and Y refers to a composition that primarily comprises X and Y, but may include small or trace amounts of components other than X and Y. In embodiments described herein, any such small or trace amounts of components other than those expressly recited following the phrase “consist(s) essentially of” or “consisting essentially of” preferably represent less than 3.0 wt % of the composition, more preferably less than or equal to 2.0 wt % of the composition, even more preferably less than or equal to 1.0 wt % of the composition, and still more preferably less than 1.0 wt % of the composition. Use of broader terms such as comprises, includes, having, etc. should be understood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, etc. Use of the term “optionally” with respect to any element of a claim is intended to mean that the subject element is required, or alternatively, is not required. Both alternatives are intended to be within the scope of the claim.

[0041] 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.

[0042] As used herein, the term “pre-manufactured” may be used to refer to a solid, monolithic component that is separately and independently manufactured, and subsequently attached to one or more other components. As used herein, the term “binderless” may be used to refer to a solid, monolithic polycrystalline diamond (PCD) component that consists of PCD (i.e., it only includes PCD and no binder such as a cobalt alloy binder or magnesium carbonate binder); and the term “substantially binderless” may be used to refer to a solid, monolithic polycrystalline diamond (PCD) component that consists essentially of PCD but may include very small or trace amounts of binder (e.g., cobalt alloy binder or magnesium carbonate binder), and more specifically, the composition of the PCD component includes less than or equal to 2.0 wt % binde, and more preferably the PCD component includes less than or equal to 1.0 wt % binder.

[0043] 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.

[0044] One factor that affects bit durability is the wear resistance of the cutter elements as sufficient wear (e.g., abrasive wear) to one or more cutter elements can detrimentally affect cutting efficiency and ROP of the drill bit. The wear resistance of an individual cutter element is often impacted by the hardness of the portion of the cutting face of the cutter element that engages and shears the formation. Conventional polycrystalline diamond (PCD) material that forms the hard-cutting layer of a cutter element is manufactured by sintering a mixture of diamond powder and a binder (e.g., a cobalt alloy) at a pressure ranging from 5 to 10 GPa. The resulting hard-cutting layer is then leached to remove the binder and increase thermal stability. Although the goal is to remove as much of the binder as reasonably possible, conventional leaching techniques can remove most but not all of the binder. This is partly due to the size limitation / constraints at higher sintering pressures, as well as the difficulties or inability to bond the PCD hard-cutting layer to a cemented tungsten carbide substrate to form the cutter element. Consequently, binderless PCD is generally not commercially available or used to form cutter elements employed in oil and gas drilling applications. However, embodiments described herein are directed to the use and incorporation of pre-manufactured binderless (or substantially binderless) PCD segments into the cutting faces of cutter elements for fixed cutter drill bits. In some embodiments described herein, one or more pre-manufactured binderless (or substantially binderless) PCD segment(s) is integrated into a relatively low cost “chassis” to form a cutter element. More specifically, the pre-manufactured binderless (or substantially binderless) PCD segments can be attached by various means to relatively low-cost carriers or substrates. Examples of pre-manufactured binderless (or substantially binderless) PCD segments than can be used in embodiments of cutter elements described herein are commercially available from Sumitomo Electric Industries, Ltd. of Osaka, Japan. Such pre-manufactured binderless (or substantially binderless) PCD segments can be mounted to a relatively low-cost cutter elements that have been previously manufactured with receiving orifices or pockets sized to receive and mate with one or more of the pre-manufactured binderless (or substantially binderless) PCD segments. The pre-manufactured binderless (or substantially binderless) PCD segment(s) can be captured and fixably secured to the cutter elements using active brazing, interference fit, low pressure HP / HT “fusing,” or other suitable mechanisms and means known in the art. The resulting assembly including the pre-manufactured binderless (or substantially binderless) PCD segment(s) and carrier or chassis can then be attached to a blade of a fixed cutter drill bit by conventional brazing, or alternatively, the carrier can be first attached to the blade of a fixed cutter drill bit by brazing followed by precision mechanical fastening of the pre-manufactured binderless (or substantially binderless) PCD segment(s) to the carrier to minimize and / or avoid any thermal damage to the carrier or mechanical assembly (e.g., softening of bolts and receiving threads etc.).

[0045] 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).

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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 three 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 three secondary blades 142 (a total of six blades 141, 142) are uniformly angularly spaced about 60° 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, and each primary blade 141 is disposed between a pair of circumferentially-adjacent secondary blades 142. Although bit 100 is shown as having three primary blades 141 and three 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 two secondary blades.

[0050] 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.

[0051] 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 elements 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 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 elements 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 elements (for example, cutter elements 200) may be arranged differently.

[0052] As will be described in more detail below, each cutter element 200 has a central axis 205, a first end 200a, and a second end 200b. First end 200a of each cutter element 200 leads the corresponding second end 200b relative to the cutting direction 106 of bit 100, and thus, each first end 200a may also be referred to herein as “leading” end 200a and each second end 200b may also be referred to herein as “trailing” end 200b. As shown in FIG. 3, each leading end 200a is proximal but positioned slightly forward of leading side 141a, 142a of the corresponding blade 141, 142, respectively, relative to cutting direction 106 of bit 100; and each trailing end 200b is distal and positioned rearward of leading side 141a, 142a of the corresponding blade 141, 142, respectively, relative to cutting direction 106 of bit 100.

[0053] Each cutter element 200 includes an elongated base or chassis 210 and a plurality of pre-manufactured polycrystalline diamond (PCD) segments 240 fixably secured to chassis 210. Each pre-manufactured PCD segment 240 is binderless or substantially binderless, and thus, may be described has having a composition consisting essentially of PCD. In this embodiment, the plurality of pre-manufactured PCD segments 240 are arranged in an axial stack.

[0054] Each chassis 210 has a central axis 215, which defines the central axis 205 of the corresponding cutter element 200, and is generally positioned and secured in the corresponding pocket 145 formed in cutter supporting surface 144 of the corresponding blade 141, 142 to which it is fixably mounted. Leading end 200a of each cutter element 200 defines a cutting surface or cutting face 202 of the corresponding cutter element 200. As will be described in more detail below, each cutting face 202 is defined by surfaces of both chassis 210 and one PCD segment 240 disposed at end 200a of cutter element 200. In this embodiment, the surfaces of chassis 210 and PCD segment 240 at end 200a are co-planar, and thus, each cutting face 202 is generally planar. In particular, co-planar surfaces of chassis 210 and PCD segment 240 at end 200a are disposed in a plane oriented perpendicular to axes 205, 215. However, in other embodiments, for any one or more of the cutter elements (e.g., cutter elements 200), the surfaces of the base (e.g., chassis 210) and the PCD segment (e.g., PCD segment 240) at the leading end of the corresponding cutter element (e.g., end 200a) may not be co-planar; the surfaces of the base and the PCD segment at the leading end of the corresponding cutter element may not be disposed in plane(s) oriented perpendicular to the central axis of the corresponding cutter element; one or more of the surfaces of the base and the PCD segment at the leading end of the corresponding cutter element may be non-planar; or combinations thereof. As used herein, the phrase “non-planar” may be used to refer to a surface 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 both. As best shown in FIG. 3, each cutter element 200 is mounted such that the corresponding central axis 205 is substantially parallel to or at an acute angle relative to the cutting direction 106 of bit 100. Such orientation results in the corresponding cutting face 202 being generally forward-facing relative to the cutting direction 106 of bit 100.

[0055] The portion of cutting face 202 of each cutter element 200 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 203 of the corresponding cutting face 202. In general, cutting tip 203, as well as the portions of cutting face 202 immediately circumferentially and radially adjacent cutting tip 203 (relative to central axis 205) of each cutter element 200 define or represent the portion of the corresponding cutting face 202 that engages and shears the formation during drilling operations. In this embodiment, each cutter element 200 is positioned and oriented relative to the corresponding blade 141, 142 such that the corresponding cutting tip 203 is located along the corresponding PCD segment 240 disposed at end 200a and defining a portion of the corresponding cutting face 202. Each cutter element 200 may be described as having an “exposure” or “extension height” measured perpendicularly from cutter-supporting surface 144 of the corresponding blade 141, 142 to the corresponding cutting tip 203.

[0056] Referring still 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 elements 200 wear slightly under gage. Gage pads 147 also help stabilize bit 100 against vibration.

[0057] Referring now to FIG. 4, an exemplary profile of blades 141, 142 (right side of FIG. 4) and an exemplary profile of cutting faces 202 (left side of FIG. 4) are shown as each would appear with blades 141, 142 and the cutting faces 202 of cutter elements 200 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 203 of cutting faces 202 of cutter elements 200 form a combined or composite cutting face profile 148b generally defined by a line passing through cutting tips 203. 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 203 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.

[0058] 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 R100 of drill bit 100. Outer radius R100 extends to and therefore defines the full gage diameter of bit 100.

[0059] 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 R100. Secondary blades 142 extend radially along bit face 111 from cone region 149a proximal nose 149d toward gage region 149c and outer radius R100. Thus, in this embodiment, each primary blade 141 and each secondary blade 142 extends substantially to gage region 149c and outer radius R100. 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.) and cutter elements (for example, cutter elements 200) are possible.

[0060] 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 elements 200 during drilling.

[0061] Referring briefly to FIGS. 2-4, on each blade 141, 142, cutter elements 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 elements 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 elements 200) may be arranged in rows with one or more cutter element having different geometries on the same blade (for example, blade 141, 142).

[0062] Referring now to FIGS. 5-7, one cutter element 200 is shown and will be described it being understood each cutter element 200 of bit 100 is the same. As previously described, cutter element 200 has a central axis 205, a first end 200a defining cutting face 202, and a second end 200b opposite end 200a. In addition, as previously described, cutter element 200 includes elongated support base or chassis 210 and the plurality of pre-manufactured PCD segments 240 fixably secured to chassis 210. Although PCD segments 240 are made of binderless or substantially binderless PCD (i.e., have compositions consisting essentially of PCD), in this embodiment, chassis 210 is entirely made of a carbide material, and in particular, a cemented tungsten carbide with cobalt.

[0063] Central axis 215 of chassis 210 is coincident and coaxially aligned with central axis 205 of cutter element 200. Chassis 210 has a first or leading end 210a at end 200a of cutter element 200, a second or trailing end 210b at end 200b of cutter element 200, and a radially outer surface 211 extending axially from leading ends 200a, 210a to trailing ends 200b, 210b. In this embodiment, leading end 210a of chassis 210 comprises and is defined by a planar surface 212, trailing end 210b of chassis 210 comprises and is defined by a planar surface 213, and outer surface 211 of chassis 210 is a cylindrical surface extending axially from leading end 210a to trailing end 210b of chassis 210. In this embodiment, each planar surface 212, 213 is disposed in a plane oriented perpendicular to central axes 205, 215. An annular chamfer or bevel 214 is provided at the intersection of planar surface 212 of chassis 210 and outer cylindrical surface 211 along cutting face 202.

[0064] Referring still to FIGS. 5-7, chassis 210 includes a recess or pocket 220 extending axially from planar surface 212 and leading end 210a. Pocket 220 has a central axis 225, an open end at end 210a of chassis 210, and a closed end axially positioned between ends 210a, 210b of chassis. Thus, pocket 220 does not extend to trailing end 210b. Central axis 225 of pocket 220 is oriented parallel to central axis 215, but radially offset and spaced from central axis 215. Pocket 220 intersects outer surface 211, and thus, pocket 220 may also be generally described as extending radially from outer surface 211.

[0065] In this embodiment, pocket 220 is cylindrical, and in particular, is defined by an inner cylindrical surface 216 of chassis 210 extending axially from planar surface 212 and an inner planar surface 217 of chassis 210 distal planar surface 212. Inner planar surface 217 is oriented perpendicular to central axis 225. As will be described in more detail below, PCD segments 240 are arranged in an axial stack 250 that is seated and secured within pocket 220, and is sized and shaped to mate with pocket 220.

[0066] In this embodiment, chassis 210 is made of two semi-cylindrical halves 218a, 218b that removably secured together via a pair of countersunk bolts 206. More specifically, halves 218a, 218b engage and meet at a plane of intersection 219 that defines the location at which halves 218a, 218b are fixably attached. In this embodiment, plane of intersection 219 is oriented parallel to axes 205, 215, contains axes 205, 215, and radially bisects chassis 210, pocket 220, and stack 250 of PCD segments 240. Bolts 206 are threadably disposed in corresponding mating, internally threaded bores that extend radially from outer surface 211 through half 218a and into half 218b. Such internally threaded bores are axially spaced (relative to axes 205, 215) and oriented perpendicular to plane of intersection 219. Further, such internally threaded bores and corresponding bolts 206 are offset and spaced from pocket 220 such that neither the internally threaded bores nor corresponding bolts 206 intersect pocket 220 or axial stack 250 of PCD segments 240. As previously described, in this embodiment, chassis 210 is entirely made of a carbide material, and in particular, a cemented tungsten carbide with cobalt. Thus, in this embodiment, each half 218a, 218b is a single-piece monolithic body entirely made of a cemented tungsten carbide with cobalt. As will be described in more details below, in other embodiments, the chassis (e.g., chassis 210) or a portion thereof (e.g., each half 218a, 218b) may be made of more than one material.

[0067] Referring still to FIGS. 5-7, as previously described, the plurality of PCD segments 240 are arranged in axial stack 250 that is seated and secured within mating pocket 220. In this embodiment, pocket 220 is cylindrical, and thus, mating stack 250 is generally cylindrical. In particular, stack 250 has a central axis 255 coaxially aligned and coincident with central axis 225 of pocket 220, a first or leading end 250a at ends 200a, 210a, a second or trailing end 250b at inner surface 217, and a radially outer cylindrical surface 251 extending axially relative to central axis 255 from first end 250a to second end 250b. In this embodiment, end 250a, 250b is defined by a planar surface 252, 253, respectively, oriented perpendicular to central axis 255. Planar surface 252 of stack 250 is coplanar with planar surface 212 of chassis 210 at end 200a of cutter element 200, planar surface 253 of stack 250 is seated flush against planar surface 217 of chassis 210, and outer cylindrical surface 251 of stack 250 is radially adjacent and contacts mating cylindrical surface 216 of chassis 210.

[0068] Stack 250 is formed by the plurality of PCD segments240 arranged axially adjacent one another (relative to central axis 255). In this embodiment, each PCD segment 240 is a cylindrical disc having a central axis 245, a first or leading end 240a, a second or trailing end 240b, and a radially outer cylindrical surface 241 extending axially (relative to central axis 245) from first end 240a to second end 240b. Each end 240a, 240b is defined by a planar surface 242, 243, respectively, oriented perpendicular to central axis 245. In this embodiment, an annular bevel or chamfer 244 is provided at the intersection of planar surface 242 at leading end 240a and radially outer cylindrical surface 241.

[0069] PCD segments 240 are stacked one atop and axially adjacent another with central axes 245 coaxially aligned with each other and central axes 255, 225 to form stack 250. Outer cylindrical surfaces 241 of PCD segments 240 define outer cylindrical surface 251 of stack 250, planar surface 242 of PCD segment 240 disposed at leading end 250a defines surface 252 of stack 250, and planar surface 243 of PCD segment 240 disposed at trailing end 250b defines planar surface 253 of stack 250. As best shown in FIGS. 6 and 7, with stack 250 of PCD segments 240 seated in mating pocket 220, stack 250 (and PCD segments 240) extend radially outwardly from pocket 220 and outer cylindrical surface 211 of chassis 210. Cutting tip 203 of cutter element 200 is circumferentially centered along a portion of PCD segment 240 at leading end 250a of stack 250 that extends radially outwardly from pocket 220 and outer cylindrical surface 211 of chassis 210.

[0070] Referring again to FIGS. 5-7, with halves 218a, 218b of chassis 210 decoupled and spaced at least slightly apart, cutter element 200 is formed by placing the axial stack 250 of PCD segments 240 in the halves of pocket 220 formed by halves 218a, 218b, and then pushing halves 218a, 218b together at plane of intersection 219. Next, bolts 206 are threadably advanced into corresponding internally threaded bores to pull and compress halves 218a, 218b together and capture stack 250 of PCD segments 240 within pocket 220 of chassis 210 with surfaces 241, 251 engaging mating cylindrical surface 216 of chassis 210 and planar surface 253 seated flush against planar surface 217 of chassis 210. Stack 250 of PCD segments may be fixably attached to body 210 within pocket 220 via interference fit within pocket 220 or brazing (e.g., active brazing) at opposed surfaces 216, 251 and opposed planar surfaces 217, 253, thereby forming cutter element 200. PCD segments 240 may be fixably attached together (e.g., via brazing opposed surfaces 242, 243 together) before or after capturing stack 250 in pocket 220. Once cutter element 200 is formed, it is seated in a pocket 145 of the corresponding blade 141, 142 and rotational oriented (about central axis 205) to define cutting tip 203 with PCD segment 240 disposed at end 250a of stack 250 as previously described, and then cutter element 200 is fixably secured to the corresponding blade 141, 142 via brazing.

[0071] During drilling operations with drill bit 100, cutting tip 203 disposed along PCD segment 240 at end 250a of stack 250 (and circumferentially and radially adjacent portions of the PCD segment 240) engages and shears the formation. As PCD segments 240 are made of binderless or substantially binderless (i.e., have compositions consisting essentially of PCD), PCD segments 240 offer the potential for enhanced wear resistance and durability during drilling as compared to conventional PCD cutting layers that include a greater wt % of binder. At a sufficient degree of wear, cutter element 200 can be removed from the corresponding blade 141, 142 and disassembled by performing the foregoing assembly steps in reverse, to replace one or more PCD segments 240 of stack 250.

[0072] In the embodiment of cutter element 200 previously described and shown in FIGS. 5-7, chassis 210 and halves 218a, 218b thereof are entirely made of single material (cemented tungsten carbide with cobalt), and further, halves 218a, 218b are fixably secured together to form chassis 210 via bolts 206. However, in other embodiments, the chassis (e.g., chassis 210) may be made of more than one material and / or the components coupled together to form the chassis (e.g., halves 218a, 218b) may be fixably secured together via means other than bolts (e.g., bolts 206).

[0073] Referring now to FIGS. 8-10, an embodiment of a cutter element 300 that can be used in place of any one or more cutter elements 200 of drill bit 100 is shown. Cutter element 300 is substantially the same as cutter element 200 previously described with the exception that the chassis of cutter element 300 is made of multiple materials and the halves of the chassis of cutter element 300 are fixably secured together via means other than bolts. For purposes of clarity and conciseness, the differences between cutter elements 200, 300 will now be described it being understood the other aspects of cutter elements 200, 300 are the same.

[0074] Referring still to FIGS. 8-10, cutter element 300 has a central axis 205, a first or leading end 200a defining a cutting face 202, and a second or trailing end 200b, each as previously described. In addition, cutter element 300 includes an elongated base or chassis 310 and a plurality of pre-manufactured PCD segments 240 as previously described arranged in an axial stack 250, which is fixably secured to base 310. Chassis 310 includes a cylindrical substrate 330 and a cylindrical disk or tablet-shaped, hard layer 336 bonded to an end of substrate 330. Substrate 330 is made entirely of a carbide material, and in particular, a cemented tungsten carbide with cobalt; and hard layer 336 has a composition comprising polycrystalline diamond (PCD) and a binder (e.g., cobalt alloy or magnesium carbonate) with the binder content of the composition ranging from 4.0 wt % to 20.0 wt %. Thus, unlike PCD segments 240 of stack 250, hard layer 336 is not made of binderless or substantially binderless PCD (i.e., hard layer 336 does not have a composition consisting essentially of PCD). Hard layer 336 and substrate 330 meet at a reference plane of intersection 335 that defines the location at which substrate 330 and hard layer 336 are fixably attached. In this embodiment, plane of intersection 335 is oriented perpendicular to axes 205, 215, and is axially positioned between leading ends 200a, 210a and trailing ends 200b, 210b. Hard layer 336 is disposed at leading end 200a and defines the portion of cutting face 202 not defined by surfaces 242, 252 at leading end 250a of stack 250 and the corresponding PCD segment 240, respectively. In particular, hard layer 336 extends axially from end 200a and cutting face 202 to plane of intersection 335, and substrate 330 extends axially from cutting layer 336 and plane of intersection 335 to trailing end 200b.

[0075] Similar to cutter element 200 previously described, chassis 310 is made of two semi-cylindrical halves 318a, 318b that engage and meet at a plane of intersection 219 that defines the location at which halves 318a, 318b are fixably attached. In this embodiment, plane of intersection 335 is oriented parallel to axes 205, 215, contains axes 205, 215, and radially bisects chassis 310, pocket 220, and stack 250 of PCD segments 240. However, unlike halves 218a, 218b of chassis 210 previously described, in this embodiment, halves 318a, 318b are fixably secured together at plane of intersection 335 via brazing.

[0076] Halves 318a, 318b of chassis 310 can be formed using high temperature, high pressure (HTHP) sintering techniques known in the art to simultaneously form and bond the corresponding halves of hard layer 336 PCD and binder to the corresponding halves of substrate 330 made of carbide. Once halves 318a, 318b are formed, cutter element 300 can be assembled in the same manner as cutter element 200 previously described with the exception that halves 318a, 318b are secured together via brazing at plane of intersection 219. The halves of pocket 220 can be formed during sintering and before securing halves 318a, 318b together, the halves of pocket 220 can be cut (e.g., with a laser) after sintering and before securing halves 318a, 318b together, or pocket 220 can be cut after sintering and after securing halves 318a, 318b together. Once formed, cutter element 300 is generally positioned and mounted to a corresponding blade of a fixed cutter drill bit (e.g., blade 141, 142 of drill bit 100) in the same manner as cutter element 200.

[0077] Cutter element 300 generally functions in the same manner as cutter element 200 during drilling operations, however, it should be appreciated that the PCD and binder forming hard layer 336 is harder and more abrasion resistant than the carbide forming substrate 330. Thus, chassis 310 of cutter element 300 including hard layer 336 at leading end 200a may enhance the abrasion resistance and durability of cutter element 300 as compared to cutter element 200, which is entirely made of carbide (including at leading end 200a).

[0078] In the embodiments of cutter element 200, 300 previously described and shown in FIGS. 5-10, an axial stack 250 of generally cylindrical, disc shaped PCD segments 240 is fixably secured to a chassis 210, 310, respectively; and chassis 210, 310 is made of halves 218a, 218b and halves 318a, 318b, respectively. However, in other embodiments, a single pre-manufactured binderless or substantially binderless PCD segment is fixably secured in a mating pocket in the chassis, the chassis may not be formed of two halves, the pre-manufactured binderless or substantially binderless PCD segment(s) may have geometries other than cylindrical, or combinations thereof.

[0079] Referring now to FIGS. 11-13, an embodiment of a cutter element 400 that can be used in place of any one or more cutter elements 200 of drill bit 100 previously described is shown. Cutter element 400 has a central axis 405, a first or leading end 400a defining a cutting face 402, and a second or trailing end 400b opposite end 400a. In addition, cutter element 400 includes elongated support base or chassis 410 and a pre-manufactured binderless or substantially binderless PCD segment 440 fixably secured to chassis 410. Thus, PCD segment 440 has a composition consisting essentially of PCD.

[0080] Chassis 410 has a central axis 415 coincident and coaxially aligned with central axis 405, a first or leading end 410a at end 400a of cutter element 400, a second or trailing end 410b at end 400b of cutter element 400, and a radially outer surface 411 extending axially from leading ends 400a, 410a to trailing ends 400b, 410b. In this embodiment, leading end 410a of chassis 410 comprises and is defined by a planar surface 412, trailing end 410b of chassis 410 comprises and is defined by a planar surface 413, and outer surface 411 of chassis 410 is a cylindrical surface extending axially from leading end 410a to trailing end 410b of chassis 410. In this embodiment, each planar surface 412, 413 is disposed in a plane oriented perpendicular to central axes 405, 415. An annular chamfer or bevel 414 is provided at the intersection of planar surface 412 of chassis 410 and outer cylindrical surface 411 along cutting face 402.

[0081] Referring still to FIGS. 11-13, in this embodiment, chassis 410 includes a cylindrical substrate 430 and a cylindrical disk or tablet-shaped, hard layer 436 bonded to an end of substrate 430. Substrate 430 is made entirely of a carbide, and in particular, a cemented tungsten carbide with cobalt; and hard layer 436 has a composition comprising polycrystalline diamond (PCD) and a binder (e.g., cobalt alloy or magnesium carbonate) with the binder content of the composition ranging from 4.0 wt % to 20.0 wt %. Thus, unlike PCD segment 440, hard layer 436 is not made of binderless or substantially binderless PCD (i.e., hard layer 436 does not have a composition consisting essentially of PCD). In this embodiment, hard layer 436 includes an axial stack of two cylindrical discs fixably attached together, each disc having a composition comprising polycrystalline diamond (PCD) and a binder (e.g., cobalt alloy or magnesium carbonate) with the binder content of the composition ranging from 4.0 wt % to 20.0 wt %.

[0082] Hard layer 436 and substrate 430 meet at a reference plane of intersection 435 that defines the location at which substrate 430 and hard layer 436 are fixably attached. In this embodiment, plane of intersection 435 is oriented perpendicular to axes 405, 415, and is axially positioned between leading ends 400a, 410a and trailing ends 400b, 410b. Hard layer 436 is disposed at leading end 400a and defines a portion of cutting face 402. In particular, hard layer 436 extends axially from end 400a and cutting face 402 to plane of intersection 435, and substrate 430 extends axially from hard layer 436 and plane of intersection 435 to trailing end 400b.

[0083] Chassis 410 includes a recess or pocket 420 extending axially from planar surface 412 and leading end 410a of chassis 410 to an inner planar surface 417 coincident with plane of intersection 435. Thus, in this embodiment, pocket 420 extends axially through hard layer 436 to substrate 430, but pocket 420 does not extend into substrate 430. Pocket 420 has a central axis 425, an open end at surface 412, and a closed end at plane of intersection 435 distal surface 412 (i.e., axially between ends 410a, 410b). Thus, pocket 420 does not extend into substrate 430 or to trailing end 410b. Central axis 425 of pocket 420 is oriented parallel to central axis 415, but is radially offset and spaced from central axis 415. Pocket 420 intersects outer surface 411, and thus, pocket 420 may also be generally described as extending radially from outer surface 411.

[0084] In this embodiment, pocket 420 is wedge-shaped. In particular, pocket 420 is defined by a first inner planar surface 416a and a second inner planar surface 416b. Each planar surface 416a, 416b extends radially from outer surface 411 of chassis 410 and extends axially from planar surface 412 at leading end 410a to inner planar surface 417 at plane of intersection 435. As pocket 420 is provided in hard layer 436 in this embodiment, each planar surface 416a, 416b may also be described as extending radially through hard layer 436 from outer surface 411 and extending axially through hard layer 436 to inner planar surface 417 and plane of intersection 435.

[0085] Planar surfaces 416a, 416b are disposed in corresponding planes that are oriented parallel to axes 405, 415, 425 and perpendicular to plane of intersection 435. The radially outer ends of surfaces 416a, 416b intersect outer surface 411 and the radially inner ends of surfaces 416a, 416b intersect radially inward of outer surface 411. In this embodiment, the radially inner ends of surfaces 416a, 416b intersect at central axes 405, 415. As best shown in FIG. 13, planar surfaces 416a, 416b of chassis 410 and hard layer 436 defining pocket 420 are angularly spaced apart about central axes 405, 415 by an angle α. In embodiments described herein, angle α preferably ranges from 30° to 180°, alternatively ranges from 45° to 120°, and alternatively ranges from 60° to 90°. In this embodiment, angle α is 90°. As will be described in more detail below, PCD segment 440 is seated and secured within pocket 420, and is sized and shaped to mate with pocket 420.

[0086] Referring still to FIGS. 11-13, as previously described, PCD segment 440 is seated and secured within mating pocket 420. In this embodiment, pocket 420 is wedge-shaped, and thus, mating PCD segment 440 is also generally wedge-shaped. In particular, PCD segment 440 has a central axis 445 coaxially aligned and coincident with central axis 425 of pocket 420, a first or leading end 440a at end 400a, a second or trailing end 440b at inner surface 417, and a radially outer surface 441 extending axially relative to central axis 445 from first end 440a to second end 440b. In this embodiment, end 440a, 440b is defined by a planar surface 442, 443, respectively, oriented perpendicular to central axis 445. Planar surface 442 of PCD segment 440 is coplanar with planar surface 412 of chassis 410 at end 400a of cutter element 400, planar surface 443 of PCD segment 440 is seated flush against planar surface 417 of chassis 410, and outer surface 441 is circumferentially adjacent and engages mating surfaces 416a, 416b of chassis 410. More specifically, outer surface 441 of PCD segment 440 includes a first planar surface 441a, a second planar surface 441b, and a cylindrical surface 441c. Each surface 441a, 44ab, 441c is oriented parallel to central axis 445, and extends axially from end 440a and associated planar surface 442 to end 440b and associated planar surface 443. Planar surface 441a extends from one end of planar surface 441b to cylindrical surface 441c, planar surface 441a extends from one end of planar surface 441b to cylindrical surface 441c, and cylindrical surface 441c extends between ends of planar surfaces 441a, 441b. As best shown in FIG. 13, with PCD segment 440 seated in mating pocket 420, planar surface 441a, 441b is circumferentially adjacent and engages mating planar surface 416a, 416b, respectively, with ends of planar surfaces 441a, 441b intersecting at central axes 405, 415 and planar surfaces 441a, 441b extending radially outward from central axes 405, 415 to cylindrical surface 441c. Thus, planar surfaces 441a, 441b are angularly spaced apart by the same angle α as planar surfaces 416a, 416b. In this embodiment. cylindrical surface 441c is disposed at the same radius as cylindrical outer surface 411 and is generally continuous and contiguous with cylindrical outer surface 411 along circumferentially adjacent hard layer 436 and axially adjacent substrate 430. Thus, in this embodiment, the transition between cylindrical outer surface 441c of PCD segment 440 and chassis 410 is smooth and continuous. In this embodiment, PCD segment 440 includes a bevel or chamfer 444 at the intersection of cylindrical outer surface 441c and planar surface 442 of PCD segment. Chamfer 444 is generally continuous and contiguous with chamfer 414 such that the transition between chamfers 414, 444 is smooth and continuous.

[0087] In one embodiment, chassis 410 is formed using high temperature, high pressure (HTHP) sintering techniques known in the art to simultaneously form hard layer 436 from powdered PCD and binder and bond the hard layer 436 (and axially stacked discs thereof) to a pre-manufactured substrate 430 made of carbide. Pocket 420 can be formed during sintering or cut (e.g., with a laser) from hard layer 436 after sintering. Once chassis 410 and pocket 420 are formed, PCD segment 440 is positioned in mating pocket 420, and fixably secured to chassis 410 via brazing between opposed planar surfaces 416a, 441a, opposed surfaces 416b, 441b, and opposed surfaces 417, 443. In another embodiment, PCD segment 440 is positioned and oriented against a pre-manufactured substrate 430 as shown in FIG. 11, and then HTHP sintering techniques known in the art can be used to form hard layer 436 from powdered PCD and binder, bond the hard layer 436 to the pre-manufactured substrate 430 made of carbide, and bond the hard layer 436 to the PCD segment 440.

[0088] Once formed, cutter element 400 is generally positioned, oriented, and mounted to a corresponding blade of a fixed cutter drill bit (e.g., blade 141, 142 of drill bit 100) such that a cutting tip 402 of cutter element 400 is located along PCD segment 440, and in particular, cutting tip 403 is circumferentially centered (relative to central axes 405, 415) along the radially outer portion of cutting face 402.

[0089] During drilling operations, cutting tip 403 disposed along PCD segment 440 engages and shears the formation. As PCD segment 440 is made of binderless or substantially binderless PCD material (i.e., PCD segment 440 has a composition consisting essentially of PCD), PCD segment 440 offer the potential for enhanced wear resistance and durability during drilling as compared to conventional PCD cutting layers that include a greater wt % of binder. Thus, cutter element 400 generally functions in the same manner as cutter element 200, however, it should be appreciated that the PCD and binder forming hard layer 436 is harder and more abrasion resistant than the carbide forming substrate 430. Thus, chassis 410 of cutter element 400 including hard layer 436 at leading end 400a may enhance the abrasion resistance and durability of cutter element 400 as compared to cutter element 200, which is entirely made of carbide (including at leading end 200a). At a sufficient degree of wear, cutter element 400 can be removed from the corresponding blade and the worn PCD segment 440 can removed by performing the foregoing assembly steps in reverse, and then replaced with a new PCD segment 440 in the same manner as previously described.

[0090] In the embodiment of cutter element 400 previously described and shown in FIGS. 11-13, pocket 420 extends axially through hard layer 436 to substrate 430 and plane of intersection 435, but does not extend axially into substrate 430. Consequently, pre-manufactured binderless or substantially binderless PCD segment 440 is seated against surface 417 of chassis 410, which is coplanar with plane of intersection 435. However, in other embodiments, the pocket (e.g., pocket 420) may extend axially through the hard layer (e.g., hard layer 436) and into the underlying substrate (e.g., substrate 430) such that the pre-manufactured binderless or substantially binderless PCD segment (e.g., PCD segment 440) seated in the pocket extends through the hard layer into the underlying substrate.

[0091] Referring now to FIGS. 14-16, an embodiment of a cutter element 500 that can be used in place of any one or more cutter elements 200 of drill bit 100 previously described is shown. Cutter element 500 is substantially the same as cutter element 400 previously described. For purposes of clarity and conciseness, the differences between cutter elements 400, 500 will now be described it being understood the other aspects of cutter elements 400, 500 are the same. Similar to cutter element 400, cutter element 500 has a central axis 405, a first or leading end 400a defining a cutting face 402, and a second or trailing end 400b opposite end 400a. In addition, cutter element 500 includes elongated support base or chassis 410 and a pre-manufactured binderless or substantially binderless PCD segment 440 fixably secured to chassis 410. PCD segment 440 is as previously described, and thus, has a composition consisting essentially of PCD. Chassis 410 is as previously described with the exception that (i) pocket 420 extends axially from leading ends 400a, 410a and cutting face 402 through hard layer 436 and across plane of intersection 435 into substrate 430, and (ii) hard layer 436 includes a single disc fixably attached to substrate 430 at plane of intersection 435. Consequently, in this embodiment, each planar surface 416a, 416b extends axially from planar surface 412 at leading ends 400a, 410a across plane of intersection 435 into substrate 430 to inner planar surface 417, and inner planar surface 417 is axially positioned between plane of intersection 435 and trailing ends 400b, 410b. Thus, each planar surface 416a, 416b is defined by surfaces extending along both hard layer 436 and substrate 430. Cutter element 500 can be assembled and functions in the same manner as cutter element 400 previously described.

[0092] In the embodiment of cutter element 300 previously described and shown in FIGS. 8-10, chassis 210 is formed of halves 218a, 218b, a plurality of PCD segments 240 are arranged in axial stack 250, PCD segments 240 are fixably attached to chassis 210 via brazing, and pocket 220 extends axially from planar surface 212 and leading end 200a, 210a through hard layer 336 and into substrate 330. As previously described, in other embodiments, the chassis may be a single-piece, monolithic body (not halves), a single PCD segment may be used (instead of an axial stack), the PCD segment(s) may be fixably attached to the chassis via means other than brazing, the pocket may not extend through the hard layer to the substrate, or combinations thereof.

[0093] Referring now to FIGS. 17-19, an embodiment of a cutter element 600 that can be used in place of any one or more cutter elements 200 of drill bit 100 previously described is shown. Cutter element 600 is similar to cutter element 300 previously described. In particular, cutter element 600 has a central axis 605, a first end 600a defining cutting face 602, and a second end 600b opposite end 600a. In addition, cutter element 600 includes elongated support base or chassis 610 and a pre-manufactured binderless or substantially binderless PCD segment 640 fixably secured to chassis 610. Thus, PCD segment 640 has a composition consisting essentially of PCD.

[0094] Chassis 610 has a central axis 615 coincident and coaxially aligned with central axis 605, a first or leading end 610a at end 600a of cutter element 600, a second or trailing end 610b at end 600b of cutter element 600, and a radially outer surface 611 extending axially from leading ends 600a, 610a to trailing ends 600b, 610b. In this embodiment, leading end 610a of chassis 610 comprises and is defined by a planar surface 612, trailing end 610b of chassis 610 comprises and is defined by a planar surface 613, and outer surface 611 of chassis 610 is a cylindrical surface extending axially from leading end 610a to trailing end 610b of chassis 610. In this embodiment, each planar surface 612, 613 is disposed in a plane oriented perpendicular to central axes 605, 615. Planar surface 612 defines a portion of cutting face 602. An annular chamfer or bevel 614 is provided at the intersection of planar surface 612 of chassis 610 and outer cylindrical surface 611.

[0095] Referring still to FIGS. 17-19, in this embodiment, chassis 610 includes a cylindrical substrate 630 and a cylindrical disk or tablet-shaped, hard layer 636 bonded to an end of substrate 630. Substrate 630 is made entirely of a carbide, and in particular, a cemented tungsten carbide with cobalt; and hard layer 636 has a composition comprising polycrystalline diamond (PCD) and a binder (e.g., cobalt alloy or magnesium carbonate) with the binder content of the composition ranging from 4.0 wt % to 20.0 wt %. Thus, unlike PCD segment 640, hard layer 636 is not made of binderless or substantially binderless PCD (i.e., hard layer 636 does not have a composition consisting essentially of PCD).

[0096] Hard layer 636 and substrate 630 meet at a reference plane of intersection 635 that defines the location at which substrate 630 and hard layer 636 are fixably attached. In this embodiment, plane of intersection 635 is oriented perpendicular to axes 605, 615, and is axially positioned between leading ends 600a, 610a and trailing ends 600b, 610b. Hard layer 636 is disposed at leading end 600a and defines a portion of cutting face 602. In particular, hard layer 636 extends axially from end 600a and cutting face 602 to plane of intersection 635, and substrate 630 extends axially from hard layer 636 and plane of intersection 635 to trailing end 600b.

[0097] Chassis 610 includes a recess or pocket 620 extending axially from planar surface 612 and leading end 610a of chassis 610 to an inner planar surface 617 axially positioned between surface 612 at leading end 610a and plane of intersection 635. Thus, in this embodiment, pocket 620 extends axially into hard layer 636. Pocket 620 has a central axis 625, an open end at surface 612, and a closed end at inner surface 617 axially positioned between surface 612 at leading end 610a and plane of intersection 635. Thus, pocket 620 does not extend to plane of intersection 635 or into substrate 630. Central axis 625 of pocket 620 is oriented parallel to central axis 615, but radially offset and spaced from central axis 615. Pocket 620 intersects outer surface 611, and thus, pocket 620 may also be generally described as extending radially from outer surface 611. In this embodiment, pocket 620 is cylindrical, and in particular, is defined by an inner cylindrical surface 616 of chassis 610 extending axially from planar surface 612 at end 610a to inner planar surface 617. Inner planar surface 617 is oriented perpendicular to central axis 625. As previously described, pocket 620 extends into hard layer 636 but not to substrate 630. Thus, surfaces 616, 617 are defined by hard layer 636.

[0098] PCD segment 640 is seated and secured within pocket 620, and is sized and shaped to mate with pocket 620. In this embodiment, pocket 620 is cylindrical, and thus, mating PCD segment 640 is generally cylindrical disc having a central axis 645, a first or leading end 640a, a second or trailing end 640b, and a radially outer cylindrical surface 641 extending axially (relative to central axis 645) from first end 640a to second end 640b. Each end 640a, 640b is defined by a planar surface 642, 643, respectively, oriented perpendicular to central axis 645. In this embodiment, an annular bevel or chamfer 644 is provided at the intersection of planar surface 642 at leading end 640a and radially outer cylindrical surface 641.

[0099] Referring still to FIGS. 17-19, PCD segment 640 is seated in mating pocket 620 with outer cylindrical surface 641 engaging mating cylindrical surface 616, planar surface 642 of PCD segment 640 disposed at leading ends 600a, 610a and defining a portion of cutting face 602, and planar surface 643 of PCD segment 640 seated against inner surface 617 of substrate 610. In this embodiment, planar surface 642 of PCD segment 640 is coplanar with planar surface 612 of chassis 610. Together, surfaces 612, 642 define cutting face 602 of cutter element 600. As pocket 620 extends radially through outer surface 611, mating PCD segment 640 extends radially outwardly from pocket 620 and outer cylindrical surface 611 of chassis 610. As will be described in more detail below, a cutting tip 603 of cutter element 600 is disposed along a portion of PCD segment 640 that extends radially outwardly from pocket 620 and outer cylindrical surface 611 of chassis 610.

[0100] In this embodiment, PCD segment 640 is fixably secured to chassis 610 within mating pocket 620 via a countersunk bolt 606. Bolt 606 extends through a central throughbore extending axially through PCD segment 640 and is threadably disposed in a mating, internally threaded bore that extends axially (relative to central axes 625, 645) through the remainer of hard layer 636 into substrate 630. The head of bolt 606 is seated in against an annular shoulder defined by a counterbore extending axially from surface 642 of PCD segment 640 to the throughbore.

[0101] Chassis 610 can be formed using high temperature, high pressure (HTHP) sintering techniques known in the art to simultaneously form hard layer 636 from powdered PCD and binder and bond the hard layer 636 to a pre-manufactured substrate 630 made of carbide. Pocket 620 can be formed during sintering or cut (e.g., with a laser) from hard layer 636 after sintering. Next, PCD segment 640 is seated in mating pocket 620, and bolt 606 is threadably advanced into corresponding internally threaded bore to secure PCD segment 640 to chassis 610 within pocket 620. In some embodiments, PCD segment 640 may be brazed to chassis 630 in addition to or as an alternative to bolt 606. In other embodiments, bolt 606 is not provided, and rather, PCD segment 640 is positioned and oriented against a pre-manufactured substrate 630 as shown in FIG. 17, and then HTHP sintering techniques known in the art can be used to form hard layer 636 from powdered PCD and binder, bond the hard layer 636 to the pre-manufactured substrate 630 made of carbide, and bond the hard layer 636 to the PCD segment 640.

[0102] Once formed, cutter element 600 is generally positioned, oriented, and mounted to a corresponding blade of a fixed cutter drill bit (e.g., blade 141, 142 of drill bit 100) such that a cutting tip 602 of cutter element 600 is located along PCD segment 640, and in particular, cutting tip 603 is circumferentially centered (relative to central axes 605, 615) along the radially outer portion of surface 642 of PCD segment 640 that extends radially outwardly from pocket 620.

[0103] During drilling operations, cutting tip 603 disposed along PCD segment 640 engages and shears the formation. As PCD segment 640 is made of binderless or substantially binderless PCD material, PCD segment 640 offers the potential for enhanced wear resistance and durability during drilling as compared to conventional PCD cutting layers that include a greater wt % of binder. Thus, cutter element 600 generally functions in the same manner as cutter element 200, however, it should be appreciated that the PCD and binder forming hard layer 636 is harder and more abrasion resistant than the carbide forming substrate 630. Thus, chassis 610 of cutter element 600 including hard layer 636 at leading end 600a may enhance the abrasion resistance and durability of cutter element 600 as compared to cutter element 200, which is entirely made of tungsten carbide (including at leading end 200a). At a sufficient degree of wear, cutter element 600 can be removed from the corresponding blade and the worn PCD segment 640 can removed by performing the foregoing assembly steps in reverse, and then replaced with a new PCD segment 640 in the same manner as previously described.

[0104] In the embodiment of cutter element 600 previously described and shown in FIGS. 17-19, chassis 610 includes one cylindrical pocket 620 and one mating cylindrical PCD segment 640 is provided. However, in other embodiments, the mating pocket and PCD segment may have other geometries (e.g., rectangular, triangular, oval, etc.) and / or more than one mating pocket and PCD segment may be provided.

[0105] Referring now to FIGS. 20-22, an embodiment of a cutter element 700 that can be used in place of any one or more cutter elements 200 of drill bit 100 previously described is shown. Cutter element 700 is similar to cutter element 600 previously described. In particular, cutter element 700 has a central axis 705, a first end 700a defining cutting face 702, and a second end 700b opposite end 700a. In addition, cutter element 700 includes elongated support base or chassis 710 and a plurality of pre-manufactured binderless or substantially binderless PCD segment 740 fixably secured to chassis 710. Thus, each PCD segment has a composition consisting essentially of PCD. In this embodiment, a pair of uniformly circumferentially-spaced PCD segments 740 are provided. Specifically, the pair of PCD segments 740 are angularly spaced 180° apart about central axis 705.

[0106] Chassis 710 has a central axis 715 coincident and coaxially aligned with central axis 705, a first or leading end 710a at end 700a of cutter element 700, a second or trailing end 710b at end 700b of cutter element 700, and a radially outer surface 711 extending axially from leading ends 700a, 710a to trailing ends 700b, 710b. In this embodiment, leading end 710a of chassis 710 comprises and is defined by a planar surface 712, trailing end 710b of chassis 710 comprises and is defined by a planar surface 713, and outer surface 711 of chassis 710 is a cylindrical surface extending axially from leading end 710a to trailing end 710b of chassis 710. In this embodiment, each planar surface 712, 713 is disposed in a plane oriented perpendicular to central axes 705, 715. Planar surface 712 defines a portion of cutting face 702. An annular chamfer or bevel 714 is provided at the intersection of planar surface 712 of chassis 710 and outer cylindrical surface 711.

[0107] Referring still to FIGS. 20-22, in this embodiment, chassis 710 includes a cylindrical substrate 630 as previously described and a cylindrical disk or tablet-shaped, hard layer 736 bonded to an end of substrate 630. As previously described, substrate 630 is made entirely of carbide, and in particular, cemented tungsten carbide and cobalt. Hard layer 736 is made entirely of PCD and a binder. Thus, unlike PCD segment 740, hard layer 736 is not made of binderless or substantially binderless PCD (i.e., hard layer 736 does not have a composition consisting essentially of PCD).

[0108] Hard layer 736 and substrate 630 meet at a reference plane of intersection 735 that defines the location at which substrate 630 and hard layer 736 are fixably attached. In this embodiment, plane of intersection 735 is oriented perpendicular to axes 705, 715, and is axially positioned between leading ends 700a, 710a and trailing ends 700b, 710b. Hard layer 736 is disposed at leading end 700a and defines a portion of cutting face 702. In particular, hard layer 736 extends axially from end 700a and cutting face 702 to plane of intersection 735, and substrate 630 extends axially from hard layer 736 and plane of intersection 735 to trailing end 700b.

[0109] Chassis 710 includes a pair of recesses or pockets 720 extending axially from planar surface 712 and leading end 710a of chassis 710. One PCD segment 740 is seated and secured within each pocket 720, and is sized and shaped to mate with the corresponding pocket 720. In this embodiment, pockets 720 are uniformly circumferentially-spaced about central axes 705, 715, and in particular, the pair of pockets 720 are angularly spaced 180° apart about central axes 705, 715; and thus, the corresponding pair of PCD segments 740 are also uniformly circumferentially spaced part, and in particular, the pair of PCD segments 740 are angularly spaced 180° apart about central axes 705, 715. In this embodiment, each pocket 720 is the same and each PCD segment 740 is the same, and thus, one pocket 720 and corresponding PCD segment 740 will be described it being understood each pocket 720 and corresponding PCD segment 740 is the same.

[0110] Pocket 720 extends axially from planar surface 712 at leading end 710a to a inner planar surface 717 axially positioned between surface 712 at leading end 710a and plane of intersection 735. Thus, in this embodiment, pocket 720 extends axially into hard layer 736. Pocket 720 has a central axis 725, an open end at surface 712, and a closed end at inner planar surface 717 axially positioned between surface 712 at leading end 710a and plane of intersection 735. Thus, pocket 720 does not extend to plane of intersection 735 or into substrate 630. Central axis 725 of pocket 720 is oriented parallel to central axis 715 but is radially offset and spaced from central axis 715. Pocket 720 intersects outer surface 711, and thus, pocket 720 may also be generally described as extending radially from outer surface 711. Unlike pocket 620 previously described, in this embodiment, pocket 720 is rectangular, and in particular, is defined by an inner prismatic rectangular surface 716 of chassis 710 extending axially from planar surface 712 at end 710a to inner planar surface 717. Prismatic rectangular surface 716 is oriented parallel to central axes 705, 715, 725, whereas inner planar surface 717 is oriented perpendicular to central axis 725. Prismatic rectangular surface 716 includes four discrete planar surfaces positioned circumferentially adjacent each other (relative to central axis 725) with each pair of circumferentially adjacent planar surfaces intersecting at an angle of 90°. As previously described, pocket 720 extends into hard layer 736 but not to substrate 730. Thus, prismatic rectangular surface 716 is defined by hard layer 736.

[0111] PCD segment 740 is seated and secured within pocket 720, and is sized and shaped to mate with pocket 720. In this embodiment, pocket 720 has a rectangular prismatic geometry, and thus, mating PCD segment 740 has a rectangular prismatic geometry with a central axis 745, a first or leading end 740a, a second or trailing end 740b, and a radially outer rectangular prismatic surface 741 extending axially (relative to central axis 745) from first end 740a to second end 740b. Each end 740a, 740b is defined by a planar surface 742, 743, respectively, oriented perpendicular to central axis 745. In this embodiment, an annular bevel or chamfer 744 is provided at the intersection of planar surface 742 at leading end 740a and radially outer rectangular prismatic surface 741.

[0112] PCD segment 740 is seated in mating pocket 720 with outer rectangular prismatic surface 741 engaging mating rectangular prismatic surface 716, planar surface 742 of PCD segment 740 disposed at leading ends 700a, 710a and defining a portion of cutting face 702, and planar surface 743 of PCD segment 740 seated against inner surface 717 of substrate 710. In this embodiment, planar surface 742 of PCD segment 740 is coplanar with planar surface 712 of chassis 710. Together, surfaces 712, 742 define cutting face 702 of cutter element 700. As pocket 720 extends radially through outer surface 711, mating PCD segment 740 extends radially outwardly from pocket 720 and outer cylindrical surface 711 of chassis 710. In this embodiment, pocket 720 and mating PCD segment 740 are rotationally oriented about central axes 725, 745 such that a corner of prismatic rectangular surface 741 is the portion of prismatic rectangular surface 741 most radial distal outer surface 711 (relative to central axes 705, 715). As will be described in more detail below, a cutting tip 703 of cutter element 700 is disposed along a portion of PCD segment 740 that extends radially outwardly from pocket 720 and outer cylindrical surface 711 of chassis 710.

[0113] In this embodiment, PCD segment 740 is fixably secured to chassis 710 within mating pocket 720 via a countersunk bolt 606. Bolt 606 extends through a central throughbore extending axially through PCD segment 740 and is threadably disposed in a mating, internally threaded bore that extends axially (relative to central axes 725, 745) through the remainer of hard layer 736 into substrate 630. The head of bolt 606 is seated in against an annular shoulder defined by a counterbore extending axially from surface 742 of PCD segment 740 to the throughbore.

[0114] Chassis 710 can be formed using high temperature, high pressure (HTHP) sintering techniques known in the art to simultaneously form hard layer 736 from powdered PCD and binder and bond hard layer 736 to a pre-manufactured substrate 630 made of carbide. Pockets 720 can be formed during sintering or cut (e.g., with a laser) from hard layer 736 after sintering. Next, PCD segments 740 are seated in mating pockets 720, and bolts 606 are threadably advanced into corresponding internally threaded bores to secure PCD segments 740 to chassis 710 within pocket 720. In some embodiments, PCD segments 740 may be brazed to chassis 730 in addition to or as an alternative to bolts 706. In other embodiments, bolts 606 are not provided, and rather, each PCD segment 740 is positioned and oriented against a pre-manufactured substrate 730 as shown in FIG. 20, and then HTHP sintering techniques known in the art can be used to form hard layer 736 from powdered PCD and binder, bond the hard layer 736 to the pre-manufactured substrate 730 made of carbide, and bond the hard layer 736 to the PCD segments 740.

[0115] Once formed, cutter element 700 is generally positioned, oriented, and mounted to a corresponding blade of a fixed cutter drill bit (e.g., blade 141, 142 of drill bit 100) such that a cutting tip 702 of cutter element 700 is located along one PCD segment 740, and in particular, cutting tip 703 is circumferentially centered (relative to central axes 705, 715) along the radially outer portion of surface 742 of such PCD segment 740 that extends radially outwardly from pocket 720.

[0116] During drilling operations, cutting tip 703 disposed along the one PCD segment 740 engages and shears the formation. As PCD segments 740 are made of binderless or substantially binderless PCD material, the PCD segment 640 defining cutting tip 703 offers the potential for enhanced wear resistance and durability during drilling as compared to conventional PCD cutting layers that include a greater wt % of binder. Thus, cutter element 700 generally functions in the same manner as cutter element 200, however, it should be appreciated that the PCD and binder forming hard layer 736 is harder and more abrasion resistant than the tungsten carbide forming substrate 630. Thus, chassis 710 of cutter element 700 including hard layer 736 at leading end 700a may enhance the abrasion resistance and durability of cutter element 700 as compared to cutter element 200, which is entirely made of tungsten carbide (including at leading end 200a). At a sufficient degree of wear, cutter element 700 can be removed from the corresponding blade and (i) the worn PCD segment 740 can removed by performing the foregoing assembly steps in reverse, and then replaced with a new PCD segment 740 in the same manner as previously described, or (ii) cutter element 700 can be rotated 180° and reattached to the corresponding blade to position that other unworn PCD segment 740 in position to perform cutting duties (i.e., to define the cutting tip 703 along the unworn PCD segment 740).

[0117] In the embodiment of cutter element 700 previously described and shown in FIGS. 20-22, chassis 710 includes two rectangular pockets 720 and two mating rectangular PCD segments 740, with one PCD segment 740 seated in one corresponding pocket 720. However, in other embodiments, an axial stack of rectangular PCD segments may be seated and fixably secured in each rectangular pocket.

[0118] Referring now to FIGS. 23-25, an embodiment of a cutter element 800 that can be used in place of any one or more cutter elements 200 of drill bit 100 previously described is shown. Cutter element 700 is substantially the same as cutter element 700 previously described with the exception that each pocket 720 extends axially to plane of intersection 735 and substrate 630, and an axial stack 750 including a plurality of axial adjacent PCD segments 740 is seated and fixably secured in each pocket 720. Cutter element 800 is formed in the same way as cutter element 700, and functions in the same manner as cutter element 700.

[0119] 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.

Claims

1. A cutter element for a fixed cutter drill bit configured to drill a borehole in a subterranean formation, the cutter element having a central axis, a leading end defining a cutting face, and a trailing end opposite the leading end, the cutter element comprising:a chassis having a central axis coaxially aligned with the central axis of the cutter element, a first end at the leading end of the cutter element, a second end at the trailing end of the cutter element, and a radially outer surface extending axially from the first end to the second end, wherein the chassis includes a pocket extending axially from the cutting face at the first end of the chassis, wherein the pocket intersects the radially outer surface of the chassis; anda pre-manufactured polycrystalline diamond (PCD) segment having a composition consisting essentially of PCD, wherein the PCD segment is disposed in the pocket and fixably secured to the chassis, wherein the PCD segment is disposed at the leading end of the cutter element and is configured to engage the formation during drilling.

2. The cutter element of claim 1, wherein the first end of the chassis comprises a planar surface oriented perpendicular to the central axis of the chassis and wherein the PCD segment comprises a planar surface at the leading end of the cutter element, wherein the planar surface of the PCD segment is coplanar with the planar surface of the chassis.

3. The cutter element of claim 1, wherein the first end of the chassis is made of tungsten carbide.

4. The cutter element of claim 3, wherein the entire chassis is made of tungsten carbide.

5. The cutter element of claim 1, wherein the chassis comprises:a cylindrical substrate having a central axis coaxially aligned with the central axis of the chassis, a first end axially proximal the leading end of the cutter element, and a second end at the trailing end of the cutter element, wherein the substrate is made of tungsten carbide; anda hard layer mounted to the first end of the substrate, wherein the hard layer extends axially from the leading end of the cutter element to the substrate, and wherein the hard layer has a composition comprising polycrystalline diamond (PCD) and a binder and defines a portion of the cutting face of the cutter element.

6. The cutter element of claim 5, wherein the pocket extends axially from the cutting face into the hard layer.

7. The cutter element of claim 5, wherein the pocket extends axially from the cutting face through the hard layer to the substrate.

8. The cutter element of claim 1, wherein the chassis comprises a pair of semi-cylindrical halves that are fixably secured together, wherein the semi-cylindrical halves engage at a plane of intersection that bisects the chassis, contains the central axis of the chassis, and bisects the pocket.

9. The cutter element of claim 1, wherein the pocket has a central axis oriented parallel to the central axis of the cutter element and radially offset from the central axis of the cutter element.

10. The cutter element of claim 9, further comprising a plurality of pre-manufactured polycrystalline diamond (PCD) segments arranged in an axial stack that is seated in the pocket and fixably secured to the chassis, wherein each PCD segment has a composition consisting essentially of PCD, and wherein the plurality of PCD segments include the PCD segment disposed at the leading end of the cutter element.

11. The cutter element of claim 1, wherein the pocket is cylindrical and the PCD segment is a cylindrical disc.

12. The cutter element of claim 1, wherein the PCD segment has a central axis oriented parallel to the central axis of the cutter element, a first end at the leading end of the cutter element, a second end distal the leading end of the cutter element;wherein the PCD segment is wedge-shaped and includes a first planar surface, a second planar surface, and a cylindrical surface, each extending axially from the first end of the pre-manufactured substantially binderless PCD segment to the second end of the pre-manufactured substantially binderless PCD segmentwherein the cylindrical surface is contiguous with a radially outer cylindrical surface of the chassis, the first planar surface extends radially from the cylindrical surface of the PCD segment to the second planar surface, and the second planar surface extends radially from the cylindrical surface of the PCD segment to the first planar surface;wherein the first planar surface and the second planar surface are angularly spaced apart by an angle α that ranges from 30° to 180°.

13. The cutter element of claim 1, wherein the PCD segment is bolted or brazed to the chassis.

14. A cutter element for a fixed cutter drill bit configured to drill a borehole in a subterranean formation, the cutter element having a central axis, a leading end defining a cutting face, and a trailing end opposite the leading end, the cutter element comprising:a chassis having a central axis coaxially aligned with the central axis of the cutter element, a first end at the leading end of the cutter element, a second end at the trailing end of the cutter element, and a radially outer cylindrical surface extending axially from the first end to the second end;a pre-manufactured polycrystalline diamond (PCD) segment having a composition consisting essentially of PCD, wherein the PCD segment is fixably secured in a pocket in the cutting face of the cutter element, and wherein the first end of the chassis defines a portion of the cutting face of the cutter element and the PCD segment defines a portion of the cutting face at the leading end of the cutter element.

15. The cutter element of claim 14, wherein the first end of the chassis comprises a planar surface oriented perpendicular to the central axis of the chassis and wherein the PCD segment comprises a planar surface at the leading end of the cutter element, wherein the planar surface of the PCD segment is coplanar with the planar surface of the chassis.

16. The cutter element of claim 14, wherein the first end of the chassis is made of tungsten carbide.

17. The cutter element of claim 14, wherein the chassis comprises:a cylindrical substrate having a central axis coaxially aligned with the central axis of the chassis, a first end axially proximal the leading end of the cutter element, and a second end at the trailing end of the cutter element, wherein the substrate is made of tungsten carbide; anda hard layer mounted to the first end of the substrate, wherein the hard layer extends axially from the leading end of the cutter element to the substrate, and wherein the hard layer has a composition comprising polycrystalline diamond (PCD) and a binder, wherein the hard layer defines a portion of the cutting face of the cutter element.

18. The cutter element of claim 17, wherein the pocket extends axially from the cutting face into the hard layer.

19. The cutter element of claim 17, wherein the pocket extends axially from the cutting face through the hard layer to the substrate.

20. The cutter element of claim 14, wherein the chassis comprises a pair of semi-cylindrical halves that are fixably secured together, wherein the semi-cylindrical halves engage at a plane of intersection that bisects the chassis, contains the central axis of the chassis, and bisects the pocket.

21. The cutter element of claim 14, wherein the pocket has a central axis oriented parallel to the central axis of the cutter element and radially offset from the central axis of the cutter element.

22. The cutter element of claim 14, further comprising a plurality of pre-manufactured polycrystalline diamond (PCD) segments arranged in an axial stack that is fixably secured in the pocket, wherein each PCD segment has a composition consisting essentially of PCD, and wherein the plurality of PCD segments include the PCD segment disposed at the leading end of the cutter element.

Images