FIXED CUTTER DRILL BITS INCLUDING CUTTER ELEMENTS WITH VARIABLE EXPOSURES

Abstract

A fixed cutter drill bit for drilling an earthen formation includes a bit body having a central axis and a bit face. The bit body is configured to rotate about the central axis in a cutting direction of rotation. The bit face includes a concave cone region extending radially from the central axis, a convex shoulder region extending radially from the cone region, a nose at the intersection of the cone region and the shoulder region, and a gage region extending radially from the shoulder region to a full gage diameter of the drill bit. The drill bit also includes a cutting structure disposed on the bit face. The cutting structure includes a primary blade extending radially from proximal the bit axis through the cone region and the shoulder region to the gage region. The blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side. In addition, the drill bit includes a plurality of high-aspect ratio cutter element assemblies mounted to the cutter-supporting surface of the primary blade in the cone region. The cutter element assemblies are arranged in a radially extending row proximal the leading side of the primary blade, wherein each cutter element assembly includes a cutter element carrier and a first cutter element fixably attached to the cutter element carrier. Still further, the drill bit includes a plurality of low-aspect ratio second cutter elements directly mounted to the cutter-supporting surface of the primary blade in the shoulder region or the gage region. The second cutter elements are arranged in a radially extending row proximal the leading side of the primary blade. Each high-aspect ratio cutter element assembly has an exposure H1 measured perpendicularly from the cutter-supporting surface of the primary blade to a cutting tip of the first cutter element of the cutter element assembly distal the primary blade. Each low-aspect ratio second cutter element has an exposure H2 measured perpendicularly from the cutter-supporting surface of the primary blade to a cutting tip of the second cutter element distal the primary blade. The exposure H1 of one or more high-aspect ratio cutter element assemblies in the cone region is greater than the exposure H2 of one or more low-aspect ratio second cutter elements in the shoulder region or the gage region.

Claims

1. A fixed cutter drill bit for drilling an earthen formation, the drill bit comprising: a bit body having a central axis and a bit face, wherein the bit body is configured to rotate about the central axis in a cutting direction of rotation, wherein the bit face includes a concave cone region extending radially from the central axis, a convex shoulder region extending radially from the cone region, a nose at the intersection of the cone region and the shoulder region, and a gage region extending radially from the shoulder region to a full gage diameter of the drill bit; a cutting structure disposed on the bit face, wherein the cutting structure includes a primary blade extending radially from proximal the bit axis through the cone region and the shoulder region to the gage region, wherein the blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side; and a plurality of high-aspect ratio cutter element assemblies mounted to the cutter-supporting surface of the primary blade in the cone region, wherein the cutter element assemblies are arranged in a radially extending row proximal the leading side of the primary blade, wherein each cutter element assembly includes a cutter element carrier and a first cutter element fixably attached to the cutter element carrier; a plurality of low-aspect ratio second cutter elements directly mounted to the cutter-supporting surface of the primary blade in the shoulder region or the gage region, wherein the second cutter elements are arranged in a radially extending row proximal the leading side of the primary blade; wherein each high-aspect ratio cutter element assembly has an exposure H1 measured perpendicularly from the cutter-supporting surface of the primary blade to a cutting tip of the first cutter element of the cutter element assembly distal the primary blade; wherein each low-aspect ratio second cutter element has an exposure H2 measured perpendicularly from the cutter-supporting surface of the primary blade to a cutting tip of the second cutter element distal the primary blade; wherein the exposure H1 of one or more high-aspect ratio cutter element assemblies in the cone region is greater than the exposure H2 of one or more low-aspect ratio second cutter elements in the shoulder region or the gage region.

2. The fixed cutter drill bit of claim 1, wherein each high-aspect ratio cutter element assembly has a longitudinal axis oriented perpendicular to the central axis, a maximum length measured parallel to the longitudinal axis in front view, and a maximum width measured perpendicular to the longitudinal axis in front view; wherein each high-aspect ratio cutter element assembly has an aspect ratio equal to the ratio of the maximum length of the high-aspect ratio cutter element assembly to the maximum width of the high-aspect ratio cutter element assembly, wherein the aspect ratio of each high-aspect ratio cutter element assembly is greater than 1.0 and less than or equal to 2.0.

3. The fixed cutter drill bit of claim 1, wherein the exposure H1 of one or more high-aspect ratio cutter element assemblies in the cone region is at least 1.5 times greater than the exposure H2 of each second cutter element in the shoulder region and the gage region.

4. The fixed cutter drill bit of claim 3, wherein the exposure H1 of each high-aspect ratio cutter element assembly in the cone region ranges from 6.0 mm to 15.0 mm and the exposure H2 of each low-aspect ratio second cutter element in the shoulder region and the gage region ranges from 5.0 mm to 20.0 mm

5. The drill bit of claim 1, wherein each pair of radially adjacent high-aspect ratio cutter element assemblies are spaced apart a minimum distance D.sub.1 measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent high-aspect ratio cutter element assemblies; wherein each pair of radially adjacent low-aspect ratio second cutter elements are spaced apart a minimum distance D.sub.2 measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent low-aspect ratio second cutter elements; wherein the spacing D.sub.1 of each pair of radially adjacent high-aspect ratio cutter element assemblies in the cone region is greater than the spacing D.sub.2 of each pair of radially adjacent low-aspect ratio second cutter elements in the shoulder region and the gage region.

6. The fixed cutter drill bit of claim 5, wherein the minimum distance D.sub.1 between each pair of radially adjacent high-aspect ratio cutter element assemblies in the cone region ranges from 4.0 mm to 20.0 mm and the minimum distance D.sub.2 between each pair of radially adjacent low-aspect ratio second cutter elements in the shoulder region and the gage region ranges from 1.0 mm to 3.0 mm.

7. The fixed cutter drill bit of claim 6, wherein the minimum distance D.sub.1 between each pair of radially adjacent high-aspect ratio cutter element assemblies in the cone region ranges from 10.0 mm to 12.0 mm.

8. The fixed cutter drill bit of claim 5, wherein the minimum distance D.sub.1 between each pair of radially adjacent high-aspect ratio cutter element assemblies in the cone region is at least 1.5 times the minimum distance D.sub.2 between each pair of radially adjacent low-aspect second cutter elements in the shoulder region and the gage region.

9. The fixed cutter drill bit of claim 8, wherein the minimum distance D.sub.1 between each pair of radially adjacent high-aspect ratio cutter element assemblies in the cone region is at least 2.0 times the minimum distance D.sub.2 between each pair of radially adjacent low-aspect ratio second cutter elements in the shoulder region and the gage region.

10. The fixed cutter drill bit of claim 1, wherein each low-aspect ratio second cutter element is cylindrical.

11. The fixed cutter drill bit of claim 1, wherein each cutter element carrier has a leading end relative to the cutting direction of rotation and a trailing end relative to the cutting direction of rotation; wherein each cutter element carrier includes a base extending axially from the leading end to the trailing end, wherein the base has an outer surface including a semi-cylindrical cutter element facing surface extending from the leading end, wherein the corresponding first cutter element is seated against the semi-cylindrical cutter element facing surface and fixably attached to the cutter element carrier.

12. The fixed cutter drill bit of claim 11, wherein each cutter element carrier further comprises a support block extending axially relative to the longitudinal axis of the high-aspect ratio cutter element assembly from the base; wherein the semi-cylindrical cutter element facing surface extends from the leading end to the support block; wherein the support block includes a leading face fixably attached to the corresponding first cutter element.

13. The fixed cutter drill bit of claim 1, wherein one or more high-aspect ratio cutter element assemblies is oriented at a non-zero tilt angle measured in a front view of the primary blade from the longitudinal axis of the high-aspect ratio cutter element assembly to a reference axis A passing through a cutting tip of the corresponding first cutter element and oriented perpendicular to a cutting profile of the plurality of high-aspect ratio cutter element assemblies and the plurality of low-aspect ratio second cutter elements mounted to the primary blade.

14. A fixed cutter drill bit for drilling an earthen formation, the drill bit comprising: a bit body having a central axis and a bit face, wherein the bit body is configured to rotate about the central axis in a cutting direction of rotation, wherein the bit face includes a concave cone region extending radially from the central axis, a convex shoulder region extending radially from the cone region, a nose at the intersection of the cone region and the shoulder region, and a gage region extending radially from the shoulder region to a full gage diameter of the drill bit; a cutting structure disposed on the bit face, wherein the cutting structure includes a plurality of circumferentially-spaced primary blades, wherein each primary blade extends radially from proximal the bit axis through the cone region and the shoulder region to the gage region, wherein each primary blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side; a plurality of gage pads, wherein each gage pad extends from an end of each primary blade distal the bit axis in the gage region; a plurality of high-aspect ratio cutter element assemblies mounted to the cutter-supporting surface of each primary blade and arranged in a row proximal the leading side of the primary blade that extends radially from proximal the bit axis through the cone region to the shoulder region, wherein each high-aspect ratio cutter element assembly includes a cutter element carrier and a first cutter element mounted to the cutter element carrier; and a plurality of low-aspect ratio second cutter elements directly mounted to the cutter-supporting surface of each primary blade and arranged in a row proximal the leading side of the primary blade that extends from the row of high-aspect ratio cutter element assemblies through the shoulder region or the gage region to the gage pad.

15. The fixed cutter drill bit of claim 14, wherein each first cutter element has a central axis, a leading end relative to the cutting direction of rotation, a trailing end relative to the cutting direction of rotation and opposite the leading end, and a cutting face at the leading end; wherein each high-aspect ratio cutter element assembly has a longitudinal axis oriented perpendicular to the central axis of the corresponding first cutter element, a maximum length measured parallel to the longitudinal axis and a maximum width measured perpendicular to the longitudinal axis; wherein each high-aspect ratio cutter element assembly has an aspect ratio equal to the ratio of the maximum length of the high-aspect ratio cutter element assembly to the maximum width of the high-aspect ratio cutter element assembly, wherein the aspect ratio of each high-aspect ratio cutter element assembly is greater than 1.0 and less than or equal to 2.0.

16. The fixed cutter drill bit of claim 14, wherein each pair of radially adjacent high-aspect cutter element assemblies on each primary blade are spaced apart a minimum distance D.sub.1 measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent high-aspect ratio cutter element assemblies; wherein each pair of radially adjacent low-aspect second cutter elements on each primary blade are spaced apart a minimum distance D.sub.2 measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent low-aspect ratio second cutter elements; wherein the minimum distance D.sub.1 between each pair of radially adjacent high-aspect ratio cutter element assemblies is greater than the minimum distance D.sub.2 between each pair of radially adjacent low-aspect ratio second cutter elements.

17. The fixed cutter drill bit of claim 16, wherein the minimum distance D.sub.1 between each pair of radially adjacent high-aspect ratio cutter element assemblies ranges from 4 mm to 20 mm and the minimum distance D.sub.2 between each pair of radially adjacent low-aspect ratio second cutter elements ranges from 1.0 mm to 3.0 mm.

18. The fixed cutter drill bit of claim 16, wherein the minimum distance D.sub.1 between each pair of radially adjacent high-aspect ratio cutter element assemblies is at least 1.5 times the minimum distance D.sub.2 between each pair of radially adjacent low-aspect ratio second cutter elements.

19. The fixed cutter drill bit of claim 14, wherein each high-aspect ratio cutter element assembly has an exposure H1 measured perpendicularly from the cutter-supporting surface of the corresponding primary blade to a cutting tip of the first cutter element of the high-aspect ratio cutter element assembly distal the corresponding primary blade; wherein each low-aspect ratio second cutter element has an exposure H2 measured perpendicularly from the cutter-supporting surface of the corresponding primary blade to a cutting tip of the low-aspect ratio second cutter element distal the corresponding primary blade; wherein the exposure H1 of one or more high-aspect ratio cutter element assemblies is greater than the exposure H2 of each low-aspect ratio second cutter element.

20. The fixed cutter drill bit of claim 19, wherein the exposure H2 of each of the low aspect-ratio second cutter element is the same; wherein the exposure H1 of the radially outermost high-aspect cutter element assembly positioned radially adjacent the row of the low-aspect ratio second cutter elements is the same as the exposure H2 of each of the low aspect-ratio second cutter elements; wherein the exposure H1 of each high-aspect ratio cutter element assembly radially positioned between the central axis of the drill bit and the radially outermost high-aspect ratio cutter element assembly is greater than the exposure H2 of each low-aspect ratio second cutter element.

21. The fixed cutter drill bit of claim 20, wherein the exposure H1 of each high-aspect ratio cutter element assembly is at least 1.25 times greater than the exposure H2 of each low-aspect ratio second cutter element.

22. The fixed cutter drill bit of claim 15, wherein one or more high-aspect ratio cutter element assembly is oriented at a non-zero tilt angle measured in a front view of the corresponding primary blade from the longitudinal axis of the high-aspect cutter element assembly to a reference axis A passing through a cutting tip of the high-aspect ratio cutter element assembly and oriented perpendicular to a cutting profile of the plurality of high-aspect ratio cutter element assemblies and the low aspect-ratio second cutter elements mounted to the primary blade.

Description

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 an enlarged, partial front view of one of the blades of the drill bit of FIG. 2;

[0017] FIG. 6 is a perspective view of one of the cutter element assemblies of the drill bit of FIG. 2;

[0018] FIG. 7 is a front view of the cutter element assembly of FIG. 6;

[0019] FIG. 8 is a side view of the cutter element assembly of FIG. 6;

[0020] FIG. 9 is a top view of the cutter element assembly of FIG. 6;

[0021] FIG. 10 is a cross-sectional side view of the cutter element assembly of FIG. 6 taken in section 10-10 of FIG. 9;

[0022] FIG. 11 is a perspective view of the cutter element carrier of FIG. 6;

[0023] FIG. 12 is an enlarged view of one primary blade and associated cutter element assemblies and cutter elements of the drill bit of FIG. 2;

[0024] FIG. 13 is a perspective view of an embodiment of a cutter element assembly in accordance with the principles described herein;

[0025] FIG. 14 is a front view of the cutter element assembly of FIG. 13;

[0026] FIG. 15 is a side view of the cutter element assembly of FIG. 13;

[0027] FIG. 16 is a top view of the cutter element assembly of FIG. 13;

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

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

[0030] FIG. 19 is a side view of the cutter element assembly of FIG. 17;

[0031] FIG. 20 is a top view of the cutter element assembly of FIG. 17;

[0032] FIG. 21 is a perspective view of an embodiment of a cutter element assembly in accordance with the principles described herein;

[0033] FIG. 22 is a front view of the cutter element assembly of FIG. 21;

[0034] FIG. 23 is a side view of the cutter element assembly of FIG. 21;

[0035] FIG. 24 is a cross-sectional side view of the cutter element assembly of FIG. 21;

[0036] FIG. 25 is a perspective view of the cutter element carrier of FIG. 21;

[0037] FIG. 26 is a perspective view of an embodiment of a cutter element assembly in accordance with principles described herein;

[0038] FIG. 27 is a front view of the cutter element assembly of FIG. 26;

[0039] FIG. 28 is a front view of the cutter element assembly of FIG. 26 with the cutter element rotated as compared to the cutter element shown in FIG. 27;

[0040] FIG. 29 is a perspective view of an embodiment of a cutter element assembly in accordance with principles described herein;

[0041] FIG. 30 is a front view of the cutter element assembly of FIG. 29; and

[0042] FIG. 31 is a perspective view of an embodiment of a cutter element assembly in accordance with principles described herein.

DETAILED DESCRIPTION

[0043] 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.

[0044] 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.

[0045] 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.

[0046] In the following discussion and in the claims, the terms including and comprising are used in an open-ended fashion, and thus should be interpreted to mean including, but not limited to . . . Also, the term couple or couples is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct engagement between the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. In addition, as used herein, the terms axial and axially generally mean along or parallel to a particular axis (e.g., central axis of a body or a port), while the terms radial and radially generally mean perpendicular to a particular axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. Still further, as used herein, the term concave refers to a curved surface that is bowed inwardly, and the term convex refers to a curved surface that is bowed outwardly. 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.

[0047] 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.

[0048] 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. One factor that significantly affects bit ROP and durability is the arrangement of the cutter elements along the face of the drill bit. For example, the exposure of cutter elements from the blades and corresponding depth-of-cut (DOC) of the cutter elements, as well as the radial spacing of cutter elements along the blades of the drill bit can impact the aggressiveness and ROP of the drill bit. More specifically, the greater the exposure of cutter elements, the greater the aggressiveness and ROP of the drill bit, and the greater the radial spacing of cutter elements, the greater the aggressiveness and ROP of the drill bit. However, the cutter elements in the radially outer portions of the drill bit usually experience more wear and damage than the cutter elements in the radially inner portions of the drill bit. Thus, overly aggressive cutter element arrangements in the radially outer portions of the bit can compromise the durability of the drill bit. Accordingly, in contrast to most conventional fixed cutter drill bits that employ uniform radial spacing and exposure of cutter elements along the radially inner and radially outer portions of the drill bit, embodiments described herein include more aggressive cutter elements having relatively larger radial spacing and exposure in the radially inner portions of the drill bit and less aggressive cutter elements with relatively smaller radial spacing and exposure in the radially outer portions of the drill bit.

[0049] 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).

[0050] 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 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.

[0051] 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.

[0052] 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.

[0053] 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. 4, in this embodiment, cutting structure 140 includes three angularly spaced-apart primary blades 141 and two angularly spaced apart secondary blades 142. Further, in this embodiment, the plurality of blades (for example, primary blades 141, and secondary blades 142) are uniformly angularly spaced on bit face 111 about bit axis 105. In particular, the three primary blades 141 and the two secondary blades 142 (a total of five blades 141, 142) are uniformly angularly spaced about 72 apart. In other embodiments, one or more of the blades may be spaced non-uniformly about bit face 111. Still further, in this embodiment, each secondary blade 142 is disposed between a pair of circumferentially-adjacent primary blades 141. Although bit 100 is shown as having three primary blades 141 and two secondary blades 142, in general, bit 100 may comprise any suitable number of primary and secondary blades. As one example only, bit 100 may comprise two primary blades and four secondary blades, or three primary blades and three secondary blades.

[0054] Referring still 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.

[0055] Each blade 141, 142 includes a cutter-supporting surface 144 that generally faces the formation during drilling and extends circumferentially from the leading side 141a to the trailing side 142 of the corresponding blade 141, 142. In this embodiment, a plurality of cutter element assemblies 200 are fixably attached to each blade 141, 142 and extend from cutter-supporting surface 144 of each blade 141, 142. Cutter element assemblies 200 are generally arranged adjacent one another in a radially extending row proximal the leading side 141a of each primary blade 141 and at least one cutter element assembly 200 is disposed proximal the radially inner end of each secondary blade 142. However, in other embodiments, the cutter element assemblies (for example, cutter element assemblies 200) may be arranged differently.

[0056] As will be described in more detail below, each cutter element assembly 200 includes a cutter element carrier 210 fixably mounted to the corresponding blade 141, 142 (e.g., via brazing such as induction brazing) and a cutter element 230 fixably secured to and carried by the carrier 210 (e.g., via brazing such as induction brazing). Each carrier 210 is made of a carbide material such as tungsten carbide. Each cutter element 230 includes an elongated and generally cylindrical support base or substrate 231 and a cylindrical disk or tablet-shaped, hard cutting layer 232 bonded to the exposed end of substrate 231. Substrate 231 has a central axis 235 and is typically made of a carbide material such as tungsten carbide, whereas cutting layer 232 is typically made of polycrystalline diamond or other superabrasive material. Cutter element 230 is received by and fixably secured in a pocket formed in the corresponding carrier 210, which in turn is received by and fixably secured in a mating socket 150 extending from the cutter-supporting surface 144 and leading side 141a, 142a of the corresponding blade 141, 142, respectively, to which it is mounted. The cylindrical disc, hard cutting layer 232 defines a cutting face 233 of the corresponding cutter element 230. In this embodiment, each cutting face 233 is the same and is planar. However, in other embodiments, one or more cutting faces (e.g., cutting faces 233) may not be completely planar, but rather, be non-planar. As used herein, the phrase non-planar may be used to refer to a cutting face that includes one or more curved surfaces (for example, concave surface(s), convex surface(s), or combinations thereof), a plurality of distinct planar surfaces that intersect at distinct edges along the cutting face, or both.

[0057] In this embodiment, a plurality of cutter elements 230, are directly attached to the corresponding blade 141, 142 without a corresponding carrier 210. Cutter elements 230 are substantially the same as cutter elements 230 previously described. Namely, each cutter element 230 includes an elongated and generally cylindrical support base or substrate 231 and a cylindrical disk or tablet-shaped, hard cutting layer 232 bonded to the exposed end of substrate 231. Cutting layer 232 of cutter element 230 is as previously described with respect to cutter element 230. Substrate 231 has a central axis 235 and is typically made of a carbide material such as tungsten carbide. Cutter elements 230 are received by and fixably secured in a mating socket 151 extending from the cutter-supporting surface 144 and leading side 141a, 142a of the corresponding blade 141, 142, respectively, to which it is mounted. Consequently, cutter elements 230 directly engage the corresponding blade 141, 142. It should be appreciated as the geometry of a stand-alone cutter element 230 is different from the geometry of a cutter element assembly 200, which includes both a cutter element 230 and a cutter element carrier 210, and thus, sockets 150, 151 have different geometries to accommodate cutter element assemblies 200 and cutter elements 230, respectively.

[0058] In the embodiments described herein, each cutter element assembly 200 is mounted such that the central axis 235 of the corresponding cutter element 230 is oriented substantially parallel to or at an acute angle relative to the cutting direction of the bit (for example, cutting direction 106 of bit 100), and similarly, each cutter element 230 is mounted such that the central axis 235 is oriented substantially parallel to or at an acute angle relative to the cutting direction of the bit (for example, cutting direction 106 of bit 100). Such orientation results in the corresponding cutting face 233 being generally forward-facing relative to the cutting direction 106 of the bit 100. The point along cutting face 233 of each cutter element 230, 230 positioned furthest from the cutter-supporting surface 144 of the corresponding blade 141, 142 as measured perpendicular to the corresponding cutter-supporting surface 144 defines a cutting tip 234 of the cutting face 233. Each cutter element assembly 200 and each cutter element 230 has an exposure or extension height H.sub.200, H.sub.230, respectively, measured perpendicularly from cutter-supporting surface 144 of the corresponding blade 141, 142 to the corresponding cutting tip 234.

[0059] Referring again to FIGS. 2 and 3, bit body 110 further includes gage pads 147 of substantially equal axial length measured generally parallel to bit axis 105. Gage pads 147 are circumferentially-spaced about the radially outer surface of bit body 110. Specifically, one gage pad 147 intersects and extends from each blade 141, 142. In this embodiment, gage pads 147 are integrally formed as part of the bit body 110. In general, gage pads 147 can help maintain the size of the borehole by a rubbing action when cutter element assemblies 200 wear slightly under gage. Gage pads 147 also help stabilize bit 100 against vibration.

[0060] Referring now to FIG. 4, an exemplary profile of blades 141, 142 (right side of FIG. 4) and an exemplary profile of cutting faces 221, 321 (left side of FIG. 4) are shown as each would appear with blades 141, 142 and cutting faces 233 rotated into a single rotated profile. In rotated profile view, blades 141, 142 form a combined or composite blade profile 148a generally defined by cutter-supporting surfaces 144 of blades 141, 142, and cutting tips 234 of cutting faces 233 form a combined or composite cutting face profile 148b generally defined by a line passing through cutting tips 234 of cutting faces 233 mounted to blades 141, 142. In this embodiment, the profiles of surfaces 144 of blades 141, 142 are generally coincident with each other, thereby forming a single composite blade profile 148a; and cutting tips 234 on different blades 141, 142 are generally disposed along the generally smooth and continuous cutting profile 148b. As shown in FIG. 4, profiles 148a, 148b have a similar shape and are generally parallel to each other when rotated into a single profile.

[0061] 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 R.sub.110 of bit body 110. Outer radius R.sub.110 extends to and therefore defines the full gage diameter of bit 100.

[0062] Referring briefly to FIGS. 3 and 5, 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 at or proximal bit axis 105 to gage region 149c and corresponding gage pads 147 extending therefrom. Secondary blades 142 extend radially along bit face 111 from cone region 149a proximal nose 149d to gage region 149c and corresponding gage pads 147 extending therefrom. Thus, in this embodiment, each primary blade 141 and each secondary blade 142 extends substantially to gage region 149c and outer radius R.sub.110. In this embodiment, secondary blades 142 extend radially inward just inside cone region 149a proximal nose 149d, and thus, secondary blades 142 occupy very little space on bit face 111 within cone region 149a. Although a specific embodiment of bit body 110 has been shown in described, one skilled in the art will appreciate that numerous variations in the size, orientation, and locations of the blades (for example, primary blades 141, secondary blades, 142, etc.), cutter element assemblies (for example, cutter element assemblies 200), and cutter elements (e.g., cutter elements 230) are possible.

[0063] 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 230, 230 during drilling.

[0064] Referring briefly to FIGS. 2-4, on each blade 141, 142, cutter element assemblies 200 and cutter elements 230 are arranged side-by-side in a row along the corresponding cutter-supporting surface 144 proximal leading side 141a, 142a. Thus, in this embodiment, cutter element assemblies 200 and cutter elements 230 are positioned radially adjacent one another (relative to bit axis 105) on a given blade 141, 142. However, in other embodiments, the cutter elements (for example, cutter element assemblies 200) may be arranged in rows with one or more cutter element having different geometries on the same blade (for example, blade 141, 142).

[0065] In general, a cutter element (e.g., cutter element 230, 230) may be described as having a radial position defined by the radial distance measured from the bit axis (e.g., bit axis 105) to the cutting tip (e.g., cutting tip 234) along the cutting face (e.g., cutting face 233) of the cutter element. It is to be understood that cutter elements arranged in a radially extending row on a given blade are disposed at different radial positions. In general, during rotation of the bit, cutter elements disposed at different radial positions on the same blade (e.g., blade 141, 142) or on different blades follow different paths that may partially overlap, whereas cutter elements disposed at the same radial positions on the same blade or on different blades follow in similar paths. Accordingly, each cutter element 230, 230 has a radial position defined by the radial distance measured from bit axis 105 to the cutting tip 234 of the cutting face 233 of the cutter element 230, 230. In addition, cutter elements 230, 230 arranged in a radially extending row on a given blade 141, 142 are disposed at different radial positions. Thus, each cutter element 230, 230 on any given blade 141, 142 has a different radial position. In this embodiment, cutter elements 230, 230 on each and every blade 141, 142 are disposed at a different radial position. In other words, in this embodiment, each cutter element 230, 230 of bit 100 is disposed at a unique radial position. However, in other embodiments, two or more cutter elements (e.g., cutter elements 230, 230) may be disposed at the same radial position.

[0066] Referring now to FIGS. 6-10, one cutter element assembly 200 will be described, it being understood the other cutter element assemblies 200 are the same. Cutter element assembly 200 has a generally stadium or obround prismatic geometry. As previously described, cutter element assembly 200 includes cutter element carrier 210 and cutter element 230 fixably mounted to carrier 210 (e.g., via brazing such as induction brazing). Cutter element 230 includes cylindrical substrate 231 and cylindrical hard cutting layer 232 bonded to the exposed end of substrate 231. Substrate 231 has a central axis 235, and cutting layer 232 defines cutting face 233. More specifically, when cutter element assembly 200 is mounted to the corresponding blade 141, 142 in mating socket 150, cutter element 230 has a leading end 230a relative to cutting direction 106 of bit 100, a trailing end 230b axially opposite end 230a (relative to axis 235), and a radially outer surface 236 extending axially from leading end 230a to trailing end 230b. Cutting face 233 is disposed at and defines leading end 230a, and trailing end 230b is defined by a planar surface 237. In this embodiment, cutting face 233 and planar surface 237 are disposed in planes oriented perpendicular to axis 235, and thus, cutting face 233 and planar surface 237 are oriented parallel to each other. In addition, in this embodiment, outer surface 236 is a cylindrical surface extending axially from leading end 230a to trailing end 230b along both cutting layer 232 and substrate 231. An annular chamfer or bevel 238 is provided at the intersection of cylindrical outer surface 236 and cutting face 233. As best shown in FIG. 10 and described in more detail below, in this embodiment, substrate 231 of cutter element 230 includes a concave indexing recess or pocket 239 along outer surface 236 at the intersection of outer surface 236 and planar surface 237 at trailing end 230b. Each cutter element 230 is the same as cutter element 230 of cutter element assembly 200 with the exception that substrate 231 of cutter element 230 does not include an indexing recess 239.

[0067] Referring now to FIGS. 6-11, cutter element carrier 210 has a first end 210a and a second end 210b opposite end 210a. When cutter element assembly 200 is seated in a mating socket 150 in blade 141, 142, first end 210a is positioned forward of and leads second end 210b relative to the cutting direction 106 of bit 100. Accordingly, first end 210a may also be referred to as leading end 210a, and second end 210b may also be referred to as trailing end 210b. Cutter element carrier 210 is generally L-shaped, monolithic member as shown in side view (FIGS. 8 and 10). In this embodiment, cutter element carrier 210 includes a base 211 extending from leading end 210a to trailing end 210b and a cutter element support member or block 220 extending from base 211 at trailing end 210b. As a result, base 211 and support block 220 define a receptacle or pocket 218 extending axially from leading end 210a of cutter element carrier 210 to support block 220. Pocket 218 is sized to receive and mate with cutter element 230.

[0068] As best shown in FIGS. 8, 10, and 11, base 211 has a central or longitudinal axis 215, a leading face 211a at end 210a, a trailing face 211b at end 210b, and a radially outer surface 212 extending axially from leading face 211a to trailing face 211b. In this embodiment, leading face 211a and trailing face 211b are defined by planar surfaces oriented perpendicular to axis 215. Outer surface 212 includes a concave cutter element facing surface 213 extending axially (relative to axis 215) from leading face 211a to support block 220, a convex blade facing surface 214 extending axially (relative to axis 215) from leading face 211a to trailing face 211b, and a pair of planar, parallel lateral side surfaces 216 extending axially (relative to axis 215) from leading face 211a to trailing face 211b. Blade facing surface 214 and cutter element facing surface 213 are radially spaced apart (relative to axis 215), and each extends laterally (relative to axis 215) between lateral side surfaces 216. Lateral side surfaces 216 are disposed along opposite lateral sides of surfaces 213, 214, extend generally circumferentially (relative to axis 215) from blade facing surface 214 to cutter element facing surface 213 (along pocket 218), and extend generally circumferentially (relative to axis 215) from blade facing surface 214 to support block 220 (rearward of pocket 218). Surfaces 213, 214, 216 extend parallel to axis 215, and thus, extend perpendicularly from leading face 211a. Cutter element facing surface 213 faces and partially defines pocket 218. In this embodiment, lateral side surfaces 216 are planar surfaces disposed in planes oriented parallel to each other, however, in other embodiments, the lateral side surfaces (e.g., surfaces 216) may not be oriented parallel to each other.

[0069] In this embodiment, cutter element facing surface 213 is a concave semi-cylindrical surface with a radius of curvature equal the radius of outer cylindrical surface 236 of cutter element 230, and blade facing surface 214 is a convex semi-cylindrical surface. As best shown in FIG. 10, outer cylindrical surface 236 of cutter element 230 is seated against, engages, and is fixably secured to mating cutter element facing surface 213. Accordingly, semi-cylindrical blade cutter element facing surface 213 defines a seat for cutter element 230. As best shown in FIG. 11, in this embodiment, a convex rounded transition surface is provided at the intersection between each lateral side surfaces 216 and cutter element facing surface 213.

[0070] Base 211 is sized and shaped to mate and slidingly engage a corresponding socket 150 in a blade 141, 142 with at least a portion of support block 220 (and cutter element 230) extending from socket 150 and cutter supporting 144 of the blade 141, 142. In particular, lateral side surfaces 216 and blade facing surface 214 engage and are fixably secured to mating surfaces defining a corresponding socket 150 in blade 141, 142 to which cutter element assembly 200 is attached.

[0071] Referring now to FIGS. 6 and 8-11, support block 220 has a central axis 225, a leading face 220a facing and partially defining pocket 218, a trailing face 220b at end 210b, and a radially outer surface 221 extending axially (relative to axis 225) from leading face 220a to trailing face 220b. Axis 225 of support block 220 is oriented parallel to axis 215 of base 211. Trailing face 220b is defined by a planar surface that is coplanar and contiguous with trailing face 211b of base 211. Thus, trailing face 211b is disposed in a plane oriented perpendicular to axes 215, 225. Leading face 220a is also defined by a planar surface. As shown in FIGS. 6 and 8-10, planar surface 237 at trailing end 230b of cutter element 230 is seated flush against the planar surface defining leading face 220a and is fixably secured thereto. In this embodiment, the planar surface defining leading face 220a is oriented perpendicular to axes 215, 225 (i.e., the planar surfaces defining faces 220a, 220b are parallel and oriented perpendicular to axes 215, 225) and axes 225, 235 are coaxially aligned, however, in other embodiments, the planar surface defining the leading face of the support block (e.g., leading face 220a of support block 220) may be oriented at an acute angle relative to a plane oriented perpendicular to the central axis of the support block (e.g., axis 225) to vary the backrake and/or siderake of cutter element 230 when coupled to a blade 141, 142, and as a result the central axis of the support (e.g., central axis 225) and central axis 235 of cutter element 230 are oriented at acute angles relative to each other.

[0072] Outer surface 221 includes a convex semi-cylindrical surface 222 extending axially (relative to axis 225) from leading face 220a to trailing face 220b, and a pair of planar, parallel lateral side surfaces 223 extending axially (relative to axis 225) from leading face 220a to trailing face 220b. Lateral side surfaces 223 are disposed along opposite lateral sides of convex semi-cylindrical surface 222, and extend from convex semi-cylindrical surface 222 to lateral side surfaces 216 of base 211. Each lateral side surface 223 of support block 220 is coplanar and contiguous with a corresponding lateral side surface 216 of base 211. In this embodiment, semi-cylindrical surface 222 of support block 220 has the same radius of curvature as semi-cylindrical surface 214 of base 211, outer cylindrical surface 236 of cutter element 230, and concave cylindrical surface 213 of base 211.

[0073] Referring now to FIGS. 10 and 11, a concave round transition surface is provided at the intersection of concave surface 213 of base 211 and leading face 220a of support 220. In addition, in this embodiment, a concave recess 217 is disposed along concave surface 213 of base 210 proximal leading face 220a of support 220. An indexing member 219 is slidingly and removably seated in mating recess 217 of base 210 and mating recess 239 of cutter element 230. In this embodiment, indexing member 219 is a ball and matting recesses 217, 239 are concave. Together, indexing member 219 and recesses 217, 239 define an indexing assembly or system for rotationally indexing and positioning of cutter element 230 when it is seated in pocket 218. Although the indexing system includes a ball indexing member 219 that is received in opposed mating recesses 217, 239 in this embodiment, in other embodiments, different indexing systems can be employed such as opposed, flush, and mating flats along the outer surfaces of the cutter element (e.g., cutter element 230) and the cutter element carrier (e.g., carrier 210); and in still yet other embodiments, no indexing system is provided to rotationally index and position the cutter element (e.g., cutter element 230) relative to the carrier (e.g., carrier 210).

[0074] As previously described, base 211 and support block 220 of cutter element carrier 210 are monolithically formed. In general, cutter element carrier 210 can be made of a material suitable for a particular application and/or to enhance durability of cutter element assembly 200. For example, carrier 210 (or portion thereof) can be made of a high strength material, a high abrasion resistant material, a corrosion resistant material, or combinations thereof. Examples of suitable materials for carrier 210 include, without limitation, steel, super alloy, cemented carbide, matrix or similar high-performance or hard material, Stellite, Inconel, Monel, metal alloys with niobium or nickel, or combinations thereof (e.g., steel, carbide, steel, hardfacing, superalloy, and carbide).

[0075] Referring now to FIGS. 6 and 10, cutter element 230 is positioned in mating pocket 218 of cutter element carrier 210 and fixably secured thereto to form cutter element assembly 200. In particular, to secure cutter element 230 to carrier 210 within mating pocket 218, cutter element 230 is disposed within pocket 218 with outer cylindrical surface 236 of cutter element 230 slidingly engaging mating semi-cylindrical concave cylindrical surface 213 of base 211, planar surface 237 at trailing end 230b of cutter element 230 slidingly engaging leading face 220a of support block 220, and recesses 217, 239 circumferentially-aligned with mating indexing member 219 disposed therein. Next, melted or wet brazing filler material is applied between adjacent surfaces 213, 236 and between adjacent planar surface 237 and leading face 220a, and the wet brazing filler material flows therebetween via capillary action. This process may be performed via induction brazing by pre-placing or hand feeding the filler material. Cutter element 230 may be moved or vibrated relative to carrier 210 during the process to allow maximal dispersion of the wet brazing filler material. However, as the brazing process is being finished, planar surface 237 is urged into flush contact with leading face 220a and surfaces 213, 236 are urged into flush contact with indexing member 219 disposed in recesses 217, 239, thereby ensuring the desired rotational orientation of cutter element 230 relative to carrier 210. As the brazing filler material cools and solidifies, cutter element 230 is fixably secured to carrier 210. In general, each cutter element assembly 200 is assembled in the foregoing manner.

[0076] It should be appreciated that cutter element 230 can be removed from pocket 218 of carrier 210 for maintenance, repair, or replacement by heating carrier 210 and/or cutter element 230 (e.g., induction heating) to melt the brazing therebetween, and then rotating and/or pulling cutter element 230 from pocket 218. In embodiments without mating indexing features (e.g., without recesses 217, 239 and indexing member 219), the cutter element (e.g., cutter element 230) can be rotated relative to the cutter element carrier (e.g., carrier 210) to position a fresh or unworn portion of the cutting edge of the cutting layer (e.g., cutting layer 232) for engaging the formation during subsequent drilling operations by heating the cutter element carrier and/or the cutter element to melt the brazing therebetween and then rotating the cutter element relative to the carrier, and then re-brazing the cutter element to the cutter element carrier as previously described. These processes for attaching cutter element 230 to carrier 210, removing cutter element 230 from carrier 210, and rotating cutter element 230 relative to carrier 210 are preferably performed without carrier 210 attached to bit 100, which offers the potential to speed the process by eliminating the need to heat and cool the entire bit 100, as well as enable the brazing to be done in a controlled lab environment separate from the bit 100. To minimize exposure of cutter element 230 to excess heat, carrier 210 can be heated and/or a heat sink applied to cutter element 230.

[0077] Once formed as described above, cutter element assembly 200 is fixably secured to drill bit 100 within a corresponding socket 150 via brazing (e.g., induction brazing). In general, each cutter element assembly 200 is mounted to a corresponding blade 141, 142 in a mating socket 150 in the foregoing manner.

[0078] Referring now to FIGS. 6-8, as previously described, in this embodiment, cutter element assembly 200 has a generally stadium or obround prismatic shape. More specifically, cutter element assembly 200 has a longitudinal axis 205 generally defined by the longitudinal axis of cutter element carrier 210. In this embodiment, longitudinal axis 205 is intersected by and oriented perpendicular to central axes 215, 225, 235 and oriented parallel to the planar surfaces defining ends 210a, 210b. In addition, in this embodiment, axes 205, 215, 225, 235 lie in a common plane that divides cutter element assembly 200 lengthwise into equal, mirror image halves. In other embodiments, longitudinal axis 205 may be intersected by and oriented perpendicular to central axes 215, 225, but may not intersected by central axis 235. In this embodiment, coplanar surfaces 216, 223 are oriented parallel to axis 205 and convex semi-cylindrical surfaces 214, 222 are intersected by longitudinal axis 215. In this embodiment, surfaces 214, 222 are intersected by longitudinal axis 215 at their respective centers that are furthest from central axes 215, 225.

[0079] As best shown in FIG. 7, cutter element assembly 200 has a maximum length L.sub.200 (in front view) measured parallel to longitudinal axes 205 between convex surfaces 214, 222 of cutter element carrier 210 and measured parallel to longitudinal axes 205 between convex surface 214 of cutter element carrier 210 and outer surface 236 of cutter element 230. In addition, cutter element assembly 200 has a maximum width W.sub.200 (in front view) measured perpendicularly to longitudinal 205, side surfaces 216, and side surfaces 223 from one side surface 216, 223 to the opposite side surface 216, 223, respectively. In this embodiment, the maximum width W.sub.200 is also equal to the outer diameter of cutter element 230. Due to the stadium prismatic shape of cutter element assembly 200, the maximum length L.sub.200 is greater than the maximum width W.sub.200. In embodiments described herein, for most drilling applications, the maximum length L.sub.200 of cutter element assembly 200 preferably ranges from 10.0 mm to 30.0 mm, and the maximum width W.sub.200 of cutter element assembly 200 is preferably greater than or equal to 5.0 mm and less than 30.0 mm. In addition, the maximum length L.sub.200 of cutter element assembly 200 is preferably at least 1.25 times the diameter of cutter element 230. In other words, the maximum length L.sub.200 of cutter element assembly 200 is preferably at least 25% greater than the diameter of cutter element 230.

[0080] Cutter element assembly 200 may also be described as having an aspect ratio equal to the ratio of the maximum length L.sub.200 of cutter element assembly 200 to the maximum width W.sub.200 of cutter element assembly 200. As the maximum length L.sub.200 is greater than the maximum width W.sub.200, the aspect ratio of cutter element assembly 200 is greater than 1.0. More specifically, in embodiments described herein, the aspect ratio of cutter element assembly 200 is greater than 1.0 and preferably less than or equal to 2.0. It should be appreciated that cylindrical cutter elements (e.g., cutter elements 230) and cylindrical cutter element assemblies have an aspect ratio of 1.0 as the length and the width of such cutter elements and cutter element assemblies are the same, and in particular, are equal to the outer diameters of such cutter elements and cutter element assemblies. For purposes of clarity and further explanation, a cutter element assembly having an aspect ratio greater than 1.0 (e.g., cutter element assembly 200) may also be referred to herein as a high-aspect ratio cutter element assembly, and a cutter element assembly (or cutter element) having an aspect ratio equal to 1.0 (e.g., cylindrical cutter element assemblies and cylindrical cutter elements) may also be referred to herein as a low-aspect ratio cutter element assembly. Thus, stadium prismatic cutter element assembly 200 is a high-aspect ratio cutter element assembly, whereas cylindrical cutter element 230 is a low-aspect ratio cutter element. In the embodiment shown in FIGS. 6-8, the maximum length L.sub.200 of cutter element assembly 200 is 25.0 mm and the maximum width W.sub.200 of cutter element assembly 200 is 16.0 mm, and thus, the aspect ratio of cutter element assembly 200 is 1.5625.

[0081] Referring now to FIGS. 2-5, as previously described, cutter element assemblies 200 and cutter elements 230 are generally arranged adjacent one another in a radially extending row proximal the leading side 141a, 142a of each primary blade 141 and each secondary blade 142, respectively. More specifically, in this embodiment, on each blade 141, 142, high-aspect ratio cutter element assemblies 200 are positioned adjacent each other along cone region 149a and at nose 149d; and low-aspect ratio cutter elements 230 are positioned along shoulder region 149b and gage region 149c of bit face 111. With the exception of up to one high-aspect ratio cutter element assembly 200 on one or more blades 141, 142 that may extend into shoulder region 149c radially adjacent nose 149d, high-aspect ratio cutter element assemblies 200 are generally not positioned along shoulder region 149b and gage region 149c of bit face 111 in this embodiment, and low-aspect ratio cutter elements 230 are generally not positioned along cone region 149a of bit face 111 in this embodiment. Collectively, cutter element assemblies 200 and cutter elements 230 on each blade 141, 142 form a single row along the blade 141, 142 with high-aspect ratio cutter element assemblies 200 forming a portion of the row extending from proximal bit axis 105 to nose 149d, and low-aspect ratio cutter elements 230 forming a portion of the row extending from shoulder region 149b radially adjacent nose 149d to outer radius R.sub.110 and the full gage diameter of bit 100. Although high-aspect cutter element assemblies 200 are positioned adjacent each other along cone region 149a and at nose 149d in the embodiment of drill bit 100, in other embodiments, the row of high-aspect cutter element assemblies 200 on one or more blades 141, 142 may extend into the shoulder region 149b or through the shoulder region 149b to gage region 149c.

[0082] Referring still to FIGS. 2-5, in embodiments described herein, the spacing between each pair of radially adjacent high-aspect ratio cutter element assemblies 200 on each blade 141, 142 (FIGS. 2, 3, and 5) and in composite cutting face profile 148b (FIG. 4) is greater than the spacing between each pair of radially adjacent low-aspect ratio cutter elements 230 on each blade 141, 142 (FIGS. 2, 3, and 5) and in composite cutting face profile 148b (FIG. 4); and further, the exposure H.sub.200 of each high-aspect ratio cutter element assembly 200 on each blade 141, 142 (FIGS. 2, 3, and 5) and in composite cutting face profile 148b (FIG. 4) is greater than the exposure H.sub.230 of each low-aspect ratio cutter element 230 on each blade 141, 142 (FIGS. 2, 3, and 5) and in composite cutting face profile 148b (FIG. 4). Without being limited by this or any particular theory, the greater the spacing of radially adjacent cutter elements, the greater the aggressiveness of the cutter elements, and the greater the exposure of cutter elements, the greater the aggressiveness of the cutter elements. Thus, in embodiments described herein, high-aspect ratio cutter element assemblies 200 are generally more aggressive than low-aspect ratio cutter element assemblies 200. It should also be appreciated that cutter elements positioned in the cone region of the bit face and proximal the nose region offer the potential to enhance ROP to a greater extent as compared to cutter elements positioned in the shoulder and gage region of the bit face; whereas cutter elements positioned in the shoulder and gage region of the bit face are more susceptible to wear as compared to cutter elements in the cone region of the bit face and proximal the nose region. Thus, the more aggressive high-aspect ratio cutter element assemblies 200 are positioned along bit face 111 in locations that offer the greatest potential to increase ROP and are less susceptible to wear.

[0083] Referring now to FIG. 5, the spacing of radially adjacent cutter element assemblies 200, the spacing of radially adjacent cutter elements 230, exposures H.sub.200 of cutter element assemblies 200, and exposures H.sub.230 of cutter elements 230 mounted to one exemplary primary blade 141 will be described it being understood cutter element assemblies 200 and cutter elements 230 on each blade 141, 142 are similarly arranged. In front view of each blade 141, 142 (i.e., when viewing leading side 141a, 142a of blade 141, 142 parallel to cutting direction 106 and perpendicular to leading side 141a, 142a), each pair of radially adjacent high-aspect ratio cutter element assemblies 200 are spaced apart a minimum distance D.sub.200 measured parallel to cutter-supporting surface 144 of the blade 141, 142 between the radially adjacent cutter element assemblies 200, and each pair of radially adjacent low-aspect ratio cutter elements 230 are spaced apart a minimum distance D.sub.230 measured parallel to cutter-supporting surface 144 of the blade 141, 142 between the radially adjacent cutter elements 230. The distance D.sub.200 between each pair of radially adjacent high-aspect ratio cutter element assemblies 200 mounted to blade 141 is greater than the distance D.sub.230 between each pair of radially adjacent low-aspect ratio cutter elements 230 mounted to blade 141. It should be appreciated that although each distance D.sub.200 is greater than each distance D.sub.230, one or more distances D.sub.200 may be different from one or more other distances D.sub.200 and one or more distances D.sub.230 may be different from one or more other distances D.sub.230. In other words, each distance D.sub.200 does not need to be the same and each distance D.sub.230 does not need to be the same. In embodiments described herein, each distance D.sub.200 ranges from about 4.0 mm to about 20.0 mm, alternatively ranges from about 6.0 mm to about 18.0 mm, alternatively ranges from about 8.0 mm to about 16.0 mm, and alternatively ranges from about 10.0 mm to about 12.0 mm; and each distance D.sub.230 ranges from 1.0 mm to 3.0 mm. Still further, in embodiments described herein, the distance D.sub.200 between each pair of radially adjacent high-aspect ratio cutter element assemblies 200 on each blade 141, 142 is at least 1.5 times the distance D.sub.230 between each pair of radially adjacent low-aspect ratio cutter elements 230 on each blade 141, 142 (i.e., 50% greater), alternatively at least 2.0 times the distance D.sub.230 between each pair of radially adjacent cutter elements 230 on each blade 141, 142 (i.e., 100% greater), alternatively at least 3 times the distance D.sub.230 between each pair of radially adjacent cutter elements 230 on each blade 141, 142 (i.e., 200% greater), alternatively at least 4 times the distance D.sub.230 between each pair of radially adjacent cutter elements 230 on each blade 141, 142 (i.e., 300% greater), alternatively at least 5 times the distance D.sub.230 between each pair of radially adjacent cutter elements 230 on each blade 141, 142 (i.e., 400% greater), and alternatively at least 6 times the distance D.sub.230 between each pair of radially adjacent cutter elements 230 on each blade 141, 142 (i.e., 500% greater). Although the distance D.sub.200 between each pair of radially adjacent high-aspect ratio cutter element assemblies 200 mounted to a given blade 141, 142 is greater than the distance D.sub.230 between each pair of radially adjacent low-aspect ratio cutter elements 230 mounted to the same blade 141, 142 in the embodiment of drill bit 100 shown and described above, in other embodiments, the distance D.sub.200 between each pair of radially adjacent high-aspect ratio cutter element assemblies 200 mounted to a given blade 141, 142 may be equal to or greater than the distance D.sub.230 between each pair of radially adjacent low-aspect ratio cutter elements 230 mounted to the same blade 141, 142.

[0084] Referring still to FIG. 5, the exposures H.sub.200, H.sub.230 of cutter element assemblies 200 and cutter elements 230, respectively, mounted to one exemplary primary blade 141 will be described it being understood the exposures H.sub.200, H.sub.230 of cutter element assemblies 200 and cutter elements 230, respectively, on each blade 141, 142 are similarly arranged. The radially outermost high-aspect ratio cutter element assembly 200 is radially adjacent the low-aspect ratio cutter elements 230 on blade 141 at or proximal nose 149d, and hence, generally marks the transition between high-aspect ratio cutter element assemblies 200 and low-aspect ratio cutter elements 230 on blade 141. Accordingly, the radially outermost high-aspect ratio cutter element assembly 200 on blade 141 may also be referred to herein as the transition high-aspect ratio cutter element assembly 200, and the remaining high-aspect ratio cutter element assemblies 200 on blade 141 may also be referred to herein as the non-transition high-aspect ratio cutter element assemblies 200. As previously described, in this embodiment, each cutter element 230, 230 is disposed at a unique radial position, and thus, cutter element 230 of each transition high-aspect ratio cutter element assembly 200 is disposed at a different and unique radial position. Consequently, the transition from high-aspect ratio cutter element assemblies 200 to low-aspect ratio cutter elements 230 on each blade 141, 142 occurs at a different and unique radial position.

[0085] In this embodiment, the exposure H.sub.200 of the transition high-aspect ratio cutter element assembly 200 on blade 141 is the same or substantially the same as the exposure H.sub.230 of each low-aspect cutter element 230 on blade 141 to ensure a generally continuous and smooth transition along cutting profile 148b between high-aspect ratio cutter element assemblies 200 and low-aspect ratio cutter elements 230. However, the exposure H.sub.200 of each non-transition high-aspect ratio cutter element assembly 200 mounted to blade 141 (i.e., each high-aspect ratio cutter element assembly 200 mounted to blade 141 other than the transition high-aspect ratio cutter element assembly 200) is greater than the exposure H.sub.230 of each low-aspect ratio cutter element 230 mounted to blade 141. Thus, the exposure H.sub.200 of each non-transition high-aspect ratio cutter element assembly 200 mounted to blade 141 is greater than the exposure H.sub.200 of the transition high-aspect ratio cutter element assembly 200 mounted to blade 141. It should be appreciated that although exposure H.sub.200 of each non-transition high-aspect ratio cutter element assembly 200 is greater than each exposure H.sub.230 of each low-aspect ratio cutter element 230, one or more exposures H.sub.200 of non-transition high-aspect ratio cutter element assemblies 200 may be different from one or more other exposures H.sub.200 and one or more exposure H.sub.230 may be different from one or more other exposure H.sub.230. In other words, exposure H.sub.200 of each non-transition high-aspect ratio cutter element assembly 200 does not need to be the same and exposure H.sub.230 of each low-aspect ratio cutter element 230 does not need to be the same. In embodiments described herein, the exposure H.sub.200 of each non-transition high-aspect ratio cutter element assembly 200 ranges from about 6.0 mm to about 15.0 mm, and alternatively ranges from 10.0 mm to 15.0 mm; and the exposure H.sub.200 of the transition high-aspect ratio cutter element assembly 200 and the exposure H.sub.230 of each low-aspect ratio cutter element 230 ranges from 5.0 mm to 13.0 mm. In addition, in embodiments described herein, the exposure H.sub.200 of each non-transition high-aspect ratio cutter element assembly 200 on each blade 141, 142 is 40% to 60% of the maximum length L.sub.200 of the high-aspect ratio cutter element assembly 200. Still further, in embodiments described herein, the exposure H.sub.200 of each non-transition high-aspect ratio cutter element assembly 200 of bit 100 is greater than 1.0 times the exposure H.sub.230 of each low-aspect ratio cutter element 230 on bit 100, alternatively at least 1.25 times the exposure H.sub.230 of each low-aspect ratio cutter element 230 on bit 100, alternatively at least 1.5 times the exposure H.sub.230 of each low-aspect ratio cutter element 230 on bit 100, and alternatively at least 1.75 times the exposure H.sub.230 of each low-aspect ratio cutter element 230 on bit 100.

[0086] Referring again to FIGS. 2-5, the high-aspect ratio cutter element assemblies 200 may be tilted to ensure and/or maintain a desired clearance with each radially adjacent cutter element assembly 200 and/or cutter element 230. More specifically as best shown in FIG. 5, the tilting of high-aspect ratio cutter element assemblies 200 mounted to one exemplary primary blade 141 will be described it being understood the high-aspect ratio cutter element assemblies 200 on each blade 141, 142 are similarly arranged. In front view of each blade 141, 142 (i.e., when viewing leading side 141a, 142a of blade 141, 142 parallel to cutting direction 106 and perpendicular to leading side 141a, 142a), one or more high-aspect ratio cutter element assemblies 200 can be tilted relative to cutting profile 148b. More specifically, one or more high-aspect ratio cutter element assemblies 200 can be oriented at a non-zero tilt angle measured from the longitudinal axis 205 of the cutter element assembly 200 to a reference axis A oriented perpendicular to cutting profile 148b at the cutting tip 234 and passing through the cutting tip 234 of the cutter element assembly 200. For purposes of clarity, for a high-aspect ratio cutter element assembly 200 with a tilt angle greater than zero (i.e., a positive tilt angle ), the longitudinal axis 205 of the cutter element assembly 200 is rotated counterclockwise relative to the corresponding reference axis A in front view; for a high-aspect ratio cutter element assembly 200 with a tilt angle less than zero (i.e., a negative tilt angle ), the longitudinal axis 205 of the cutter element assembly 200 is rotated clockwise relative to the corresponding reference axis A in front view; and for a high-aspect ratio cutter element assembly 200 with a tilt angle equal to zero (i.e., a cutter element that is not tilted), the longitudinal axis 205 of the cutter element assembly 200 is coincident with the corresponding reference axis A in front view. In embodiments described herein, the tilt angle of each high-aspect ratio cutter element assembly 200 ranges from 0 to +/45, and preferably ranges from 0 to +/15. In the embodiment of bit 100 shown in FIGS. 2-5, each high-aspect cutter element assembly 200 on each blade 141, 142 is oriented at a positive tilt angle , and more particularly, oriented at a tilt angle of +10. However, in other embodiments, one or more high-aspect ratio cutter element assemblies 200 on a given blade 141, 142 and/or different blades 141, 142 may be oriented at a positive tilt angle , one or more high-aspect ratio cutter element assemblies 200 on a given blade 141, 142 and/or different blades 141, 142 may be oriented at a negative tilt angle , one or more high-aspect ratio cutter element assemblies 200 on a given blade 141, 142 and/or different blades 141, 142 may be oriented at a tilt angle of 0, or combinations thereof. In addition, the tilt angles of any two or more high-aspect ratio cutter element assemblies 200 on a given blade 141, 142 and/or different blades 141, 142 may be the same or different.

[0087] As compared to a conventional cylindrical cutter element directly mounted to a blade (e.g., cutter element 230 directly mounted to blade 141, 142), embodiments of the high-aspect ratio cutter element assemblies described herein including a similarly sized cutter element (e.g., cutter element assembly 200 including cutter element 230 of similar size to cutter element 230) offer the potential for an increased exposure (e.g., exposure H.sub.200) and hence aggressiveness, while still ensuring sufficient retention to the corresponding blade. In addition, by including a conventional cylindrical cutter element with a cylindrical diamond hard cutting layer (e.g., cutter element 230 with hard cutting layer 232) as opposed to a cutter element with a stadium-shaped or other non-cylindrical shaped hard cutting layer, embodiments of cutter element assemblies described herein do not require the manufacture of non-cylindrical hard cutting layers, which generally more difficult to manufacture as compared to cylindrical hard cutting layers. Still further, as is known in the art, the greater the surface area of the cutting face (e.g., cutting face 233) of the hard cutting layer (e.g., hard cutting layer 232), the lesser the sintering pressure during manufacture of the hard cutting layer and the lesser the resulting density of the hard cutting layer. Thus, by including a conventional cylindrical hard cutting layer (e.g., hard cutting layer 232 of cutter element 230) as opposed to a high-aspect ratio hard cutting layer with a similar width but greater length and surface area, embodiments of cutter element assemblies described herein offer the potential to exhibit greater durability due to the relatively denser hard cutting layer.

[0088] Referring again to FIGS. 2 and 3, cutter element assemblies 200 and cutter elements 230 are disposed in mating sockets 150, 151, respectively, in blades 141, 142 and extend from cutter-supporting surfaces 144 of blades 141, 142 to an extension height H.sub.200, H.sub.230, respectively, as previously described. In addition, the rear or trailing end of the portion of each high-aspect ratio cutter element assembly 200 extending from cutter-supporting surface 144 of the corresponding blade 141, 142 is engaged by a back support 160 that extends or projects perpendicularly from the cutter supporting surface 144; and the rear or trailing end of the portion of each low-aspect ratio cutter element 230 extending from cutter-supporting surface 144 of the corresponding blade 141, 142 is engaged by a back support 170 that extends or projects perpendicularly from the cutter supporting surface 144. Back supports 160, 170 are integral with and monolithically formed with the corresponding blade 141, 142, and generally function to support cutter element assemblies 200 and cutter elements 230 during drilling operations.

[0089] Referring now to FIG. 12, one exemplary back support 160 and one exemplary back support 170 of one exemplary primary blade 141 will be described it being understood that back supports 160, 170 on each blade 141, 142 is generally the same. Back support 160, 170 has a central axis 165, 175, respectively, a front or leading end 160a, 170a, respectively, relative to cutting direction 106, a rear or trailing end 160b, 170b, respectively, relative to cutting direction 106, and an outer surface 161, 171, respectively, extending axially (relative to the corresponding axis 165, 175) from the leading end 160a, 170a, respectively, to trailing end 160b, 170b, respectively.

[0090] As extension heights H.sub.200 of the non-transition high-aspect ratio cutter element assemblies 200 are greater than the extension heights H.sub.230 of the low-aspect ratio cutter elements 230, and the minimum distance D.sub.200 between radially adjacent high-aspect ratio cutter element assemblies 200 is greater than the minimum distance D.sub.230 between the radially adjacent low-aspect ratio cutter elements 230, high-aspect ratio cutter element assemblies 200 generally experience greater impact loads (forces oriented perpendicular to cutting faces 233) during drilling operations as compared to the impact loads experienced by low-aspect ratio cutter elements 230 (forces oriented perpendicular to cutting faces 233) during drilling operations. Accordingly, in embodiments described herein, back supports 160 supporting high-aspect ratio cutter element assemblies 200 are larger and more robust than back supports 170 supporting low-aspect ratio cutter elements 230 to enable back supports 160 to support the greater loads experienced by high-aspect ratio cutter element assemblies 200 as compared to low-aspect ratio cutter elements 230. In particular, leading ends 160a, 170a of back supports 160, 170 are generally contiguous and have the same cross-sectional profile (in a plane oriented perpendicular to central axis 165, 175, respectively) as the trailing end of the portion of the corresponding cutter element assembly 200 and cutter element 230, respectively, that extends from the corresponding cutter supporting surface 144. Thus, at leading end 160a, 170a, outer surface 161, 171, respectively, is generally contiguous with outer surface of the trailing end of the portion of the corresponding cutter element assembly 200 and cutter element 230, respectively, that extends from the corresponding cutter supporting surface 144. Moving axially relative to central axis 165, 175 from leading end 160a, 170a, respectively, to trailing end 160b, 170b, respectively, the portion of the outer surface 161, 171, respectively, of each back support 160, 170, respectively, distal the corresponding cutter-supporting surface 144 continuously curves or slopes toward the corresponding cutter-supporting surface 144, and the lateral sides of the outer surface 161, 171, respectively, of each back support 160, 170, respectively, that extend from the corresponding cutter-supporting surface 144 on opposite sides of central axis 165, 175, respectively, continuously slope or taper radially inwardly toward central axis 165, 175, respectively. However, each back support 160 has a length L.sub.160 measured axially relative to central axis 165 from leading end 160a to trailing end 160b that is greater than a length L.sub.170 of each back support 170 measured axially relative to central axis 175 from leading end 170a to trailing end 170b. In addition, as the exposure H.sub.200 of each non-transition high-aspect ratio cutter element assembly 200 is greater than the exposure H.sub.230 of each low-aspect ratio cutter element 230, back supports 160 extend perpendicularly from the corresponding cutter-support surface 144 further than back supports 170 of low-aspect ratio cutter elements 230. In other words, back supports 160 are taller and longer than back supports 170. Thus, back supports 160 associated with high-aspect ratio cutter element assemblies 200 are generally longer, larger, and more robust than back supports 170 associated with low-aspect ratio cutter elements 230.

[0091] Referring now to FIGS. 3 and 12, due to the rotation of drill bit 100 about central axis 105 and the axial advancement of drill bit 100 along central axis 105 during drilling operations, each cutter element assembly 200 and cutter element 230 generally moves in a helical path during drilling operations. Due to the extended length L.sub.160 and height (relative to the corresponding cutter-supporting surface 144) of each back support 160 associated with a corresponding high-aspect ratio cutter element assembly 200 as compared to the shorter length L.sub.170 and height (relative to the corresponding cutter-supporting surface 144) of each back support 170 associated with a corresponding low-aspect ratio cutter element 230, outer surfaces 161 of the relatively large back supports 160 are more susceptible to undesirable engagement and rubbing against the formation within the kerf cut by the associated cutter element assembly 200. Accordingly, in embodiments described herein, central axis 165 and outer surface 161 of each back support 160 follows a curved helical path (i) generally disposed and centered at the radial position of the corresponding high-aspect ratio cutter element assembly 200, and (ii) with the portion of outer surface 161 distal the corresponding cutter-supporting surface 144 continuously sloping toward the cutter-supporting surface 144 moving axially (relative to central axis 165) from leading end 160a to trailing end 160b to prevent and/or reduce the likelihood of outer surface 161 undesirable rubbing against the formation within the kerf cut by the associated cutter element assembly 200.

[0092] As previously described, cutter element 230 is fixably secured to carrier 210 to form cutter element assembly 200, and carrier 210 of cutter element assembly 200 is disposed in a mating socket 150 in a blade 141, 142 and fixably attached to the blade 141, 142 to fixably secure cutter element assembly 200 thereto. In general, the orientation of cutter element 230 relative to carrier 210 and/or the orientation of cutter element assembly 200 relative to the blade 141, 142 to which it is mounted can be varied to control and define the backrake and siderake of cutter element 230 of cutter element assembly 200. It may be preferred to adjust the orientation of cutter element 235 relative to carrier 210 than to adjust the orientation of cutter element assembly 200 relative to the blade 141, 142 to vary the backrake and/or siderake of cutter element 230 as the geometry and orientation of sockets 150 in blades 141, 142 may be more difficult to alter, and cutter element assemblies 200 can be removed and replaced with relative ease as described above. As will now be described, FIGS. 13-20 illustrate alternative embodiments cutter element assemblies that are substantially the same as cutter element assembly 200, but provide a different backrake (FIGS. 13-16) and different side rake (FIGS. 17-20) for cutter element 230 when mounted to a blade 141, 142.

[0093] Referring now to FIGS. 13-16, an embodiment of a cutter element assembly 300 is shown. In general, cutter element assembly 300 can be mounted to drill bit 100 in place of any one or more cutter element assemblies 200. Cutter element assembly 300 is substantially the same as cutter element assembly 200 previously described with the exception that the backrake of cutter element 230 is varied. More specifically, cutter element assembly 300 includes a cutter element carrier 310 and a cutter element 230 fixably attached to carrier 310. Cutter element 230 is as previously described. Cutter element carrier 310 is similar to cutter element carrier 210 previously described. In particular, cutter element carrier 310 includes a base 211 as previously described and a support block 220 as previously described extending from base 211. However, in this embodiment, the orientation of the surfaces defining pocket 218 (i.e., the planar surface defining leading face 220a of support block 220 and concave semi-cylindrical surface 213 of base 211) are adjusted to increase the backrake of cutter element 230. As best shown in the side view of FIG. 15, the planar surface defining leading face 220a slopes rearwardly toward trailing face 220b moving axially (relative to longitudinal axis 205) from concave semi-cylindrical cutter element facing surface 213 to convex semi-cylindrical surface 222. In addition, semi-cylindrical cutter element facing surface 213 extends perpendicularly to the planar surface defining leading face 220a, and thus, slopes upward generally away from central axis 215 and blade facing surface 214 (and toward central axis 225) moving axially (relative to central axis 225) from the planar surface defining leading face 220a to end 210a and leading face 211a of base 211.

[0094] Due to the orientations of the planar surface defining leading face 220a of support block 220 and concave semi-cylindrical cutter element facing surface 213, pocket 218 slopes upward generally away from central axis 215 and blade facing surface 214 moving axially (relative to central axis 225) from the planar surface defining leading face 220a to end 210a and leading face 211a of base 211. As a result, when cutter element 230 is disposed in mating pocket 218, cutter element 230 and axis 235 also slope upward generally away from central axis 215 and blade facing surface 214 moving axially (relative to central axis 225) from trailing end 230b to leading end 230a, and consequently, cutting face 233 at leading end 230a is tilted rearwardly moving axially (relative to longitudinal axis 205) along cutting face 233 from base 211 to cutting tip 234.

[0095] In general, cutter element assembly 300 is formed and mounted to a blade 141, 142 in the same manner as cutter element assembly 200 previously described. However, as cutting face 233 at leading end 230a is tilted rearwardly moving axially (relative to longitudinal axis 205) along cutting face 233 from base 211 to cutting tip 234, as compared to cutter element assembly 200, when cutter element assembly 300 is mounted to a blade 141, 142 in a socket 150, cutter element 230 of cutter element assembly 200 will have an increased backrake as compared to cutter element 230 of cutter element assembly 200.

[0096] Referring now to FIGS. 17-20, an embodiment of a cutter element assembly 400 is shown. In general, cutter element assembly 400 can be mounted to drill bit 100 in place of any one or more cutter element assemblies 200. Cutter element assembly 400 is substantially the same as cutter element assembly 200 previously described with the exception that the siderake of cutter element 230 is varied. More specifically, cutter element assembly 400 includes a cutter element carrier 410 and a cutter element 230 fixably attached to carrier 410. Cutter element 230 is as previously described. Cutter element carrier 410 is similar to cutter element carrier 210 previously described. In particular, cutter element carrier 410 includes a base 211 as previously described and a support block 220 as previously described extending from base 211. However, in this embodiment, the orientation of the surfaces defining pocket 218 (i.e., the planar surface defining leading face 220a of support block 220 and concave semi-cylindrical surface 213 of base 211) are adjusted to alter the siderake of cutter element 230. As best shown in the side view of FIG. 19 and the top view of FIG. 20, the planar surface defining leading face 220a slopes rearwardly toward trailing face 220b moving radially and laterally (relative to central axis 225) from one lateral side surface 223 (also labeled 223 in FIGS. 17-20) to the other lateral side surface 223 (also labeled 223 in FIGS. 17-20). In addition, semi-cylindrical cutter element facing surface 213 extends perpendicularly to the planar surface defining leading face 220a, and thus, slopes laterally generally away from one lateral side surface 216 of base 211 (also labeled 216 in FIGS. 17-20) and toward the other lateral side surface 216 of base 211 (also labeled 216 in FIGS. 17-20) moving axially (relative to axes 215, 225 from leading face 220a of support block 220 to leading face 211a of base 211.

[0097] Due to the orientations of the planar surface defining leading face 220a of support block 220 and concave semi-cylindrical cutter element facing surface 213, pocket 218 slopes generally away from central axis 225 and lateral side surfaces 216, 223 moving axially (relative to axes 215, 225 from leading face 220a of support block 220 to leading face 211a of base 211. As a result, when cutter element 230 is disposed in mating pocket 218, cutter element 230 and axis 235 also slope generally away from central axis 225 and lateral side surfaces 216, 223 moving axially (relative to axes 225, 235 from trailing end 230b to leading end 230a, and consequently, cutting face 233 at leading end 230a is tilted laterally moving radially and laterally (relative to central axis 225) along cutting face 233 from side surfaces 216, 223 to side surfaces 216, 223.

[0098] In general, cutter element assembly 400 is formed and mounted to a blade 141, 142 in the same manner as cutter element assembly 200 previously described. However, as cutting face 233 at leading end 230a is tilted laterally moving radially and laterally (relative to central axis 225) along cutting face 233 from side surfaces 216, 223 to side surfaces 216, 223, as compared to cutter element assembly 200, when cutter element assembly 400 is mounted to a blade 141, 142 in a socket 150, cutter element 230 of cutter element assembly 200 be disposed at a different siderake as compared to cutter element 230 of cutter element assembly 200.

[0099] In the embodiments of cutter element assemblies 200, 300, 400 previously described, cutter element carrier 210 includes base 211 and support block 220 extending axially (relative to longitudinal axis 205) from base 211. However, in other embodiments, support block 220 may be eliminated. For example, referring now to FIGS. 21-24, an embodiment of a cutter element assembly 500 that can be mounted to drill bit 100 in place of any one or more cutter element assemblies 200 is shown. Cutter element assembly 400 is substantially the same as cutter element assembly 200 previously described with the exception that support block 220 is eliminated. More specifically, cutter element assembly 500 includes a cutter element carrier 510 and a cutter element 230 as previously described fixably mounted thereto. Cutter element carrier 510 has a first or leading end 510a and a second or trailing end 510b. In addition, cutter element carrier 510 includes a base 511, however, in this embodiment, carrier 510 does not include a support block extending from base 511 (i.e., cutter element carrier 510 does not include support block 220). Base 511 is the same as base 211 previously described. Namely, base 511 has a central or longitudinal axis 515, a leading face 511a at end 510a, a trailing face 511b at end 510b, and a radially outer surface 512 extending axially from leading face 511a to trailing face 511b. Leading face 511a and trailing face 511b are defined by planar surfaces oriented perpendicular to axis 515. Outer surface 512 includes a concave cutter element facing surface 213 extending axially (relative to axis 515) from leading face 511a to trailing face 511b as best shown in FIGS. 24 and 25, a convex blade facing surface 214 extending axially (relative to axis 515) from leading face 511a to trailing face 511b, and a pair of planar, parallel lateral side surfaces 216 extending axially (relative to axis 515) from leading face 511a to trailing face 511b. Surfaces 213, 214, 216 are each as previously described. Thus, blade facing surface 214 and cutter element facing surface 213 are radially spaced apart (relative to axis 515), and each extends laterally (relative to axis 515) between lateral side surfaces 216. Lateral side surfaces 216 are disposed along opposite lateral sides of surfaces 213, 214, extend generally circumferentially (relative to axis 515) from blade facing surface 214 to cutter element facing surface 213. Surfaces 213, 214, 216 are oriented parallel to axis 515, and thus, extend perpendicularly from leading face 511a to trailing face 511b. As cutter element carrier 510 does not include support block 220, in this embodiment, cutter element carrier 510 is completely defined by base 511, and further, both cutter element carrier 510 and base 511 have a generally crescent moon prismatic shapes.

[0100] As previously described, cutter element facing surface 213 is a concave semi-cylindrical surface with a radius of curvature equal the radius of outer cylindrical surface 236 of cutter element 230, and blade facing surface 214 is a convex semi-cylindrical surface. As best shown in FIGS. 22 and 24, outer cylindrical surface 236 of cutter element 230 is seated against, engages, and is fixably secured to mating cutter element facing surface 213. Accordingly, in this embodiment, cutter element facing surface 213 faces and defines a pocket 518 and seat that receives mating cutter element 230. Cutter element 230 is fixably attached to base 511 in the same manner as previously described.

[0101] Base 511 is sized and shaped to mate and slidingly engage a corresponding socket 150 in a blade 141, 142 with at least a portion of cutter element 230 extending from socket 150 and cutter supporting 144 of the blade 141, 142. In particular, lateral side surfaces 216 and blade facing surface 214 engage and are fixably secured to mating surfaces defining a corresponding socket 150 in blade 141, 142 to which cutter element assembly 500 is attached.

[0102] Referring now to FIGS. 26 and 27, another embodiment of a high-aspect ratio cutter element assembly 600 that can be used in place of one or more cutter element assemblies 200 on bit 100 is shown. Cutter element assembly 600 is substantially the same as cutter element assembly 200 previously described. In particular, cutter element assembly 600 includes a cutter element carrier 610 and a cutter element 630 fixably mounted to carrier 610 (e.g., via brazing such as induction brazing). Cutter element 630 includes cylindrical substrate 631 and cylindrical hard cutting layer 632 bonded to the exposed end of substrate 631. Substrate 631 and cutting layer 632 are substantially the same as substrate 231 and cutting layer 232, respectively, as previously described. Specifically, substrate 631 has a central axis 635, and cutting layer 632 defines a cutting face 633 of cutter element 630. When cutter element assembly 600 is mounted to the corresponding blade 141, 142 in mating socket 150, cutter element 630 has a leading end 630a relative to cutting direction 106 of bit 100, a trailing end 630b axially opposite end 630a (relative to axis 635), and a radially outer surface 636 extending axially from leading end 630a to trailing end 630b. Cutting face 633 is disposed at and defines leading end 630a, and trailing end 630b is defined by a planar surface 637. In this embodiment, cutting face 633 and planar surface 637 are disposed in planes oriented perpendicular to axis 635, and thus, cutting face 633 and planar surface 637 are oriented parallel to each other. In addition, in this embodiment, outer surface 636 is a cylindrical surface extending axially from leading end 630a to trailing end 630b along both cutting layer 632 and substrate 631. An annular chamfer or bevel 638 is provided at the intersection of cylindrical outer surface 636 and cutting face 633.

[0103] Unlike cutter element 230 previously described, in this embodiment, a pair of circumferentially-spaced planar flats or surfaces 639 extend axially (relative to central axis 635) along cylindrical outer surface 636 from leading end 630a and cutting face 633 across cutting layer 632 and a portion of substrate 631. Bevel 638 extends along the intersection between each planar flat 639 and cutting face 633. Thus, each planar flat 639 has a first or leading end 639a along outer surface 636 of cutting layer 631 adjacent bevel 638 and cutting face 633, and a second or trailing end 639b along outer surface 636 of substrate 631 distal cutting face 633. Each planar flat 639 slopes radially outwardly relative to central axis 635 as it extends generally axially relative to central axis 635 from leading end 639a to trailing end 639b. In this embodiment, planar flats 639 are positioned on opposite sides of a reference plane that contains axis 635 and bisects cutter element 630 into mirror image halves. Thus, planar flats 639 are symmetric across the reference plane. In addition, unlike cutter element 230 previously described, in this embodiment, substrate 631 does not include concave indexing recess 239 along outer surface 636. Rather, as will be described in more detail below, cutter element assembly 600 includes an alternative indexing system to aid in rotationally orienting cutter element 630 relative to cutter element carrier 610.

[0104] Referring still to FIGS. 26 and 27, cutter element carrier 610 is substantially the same as cutter element carrier 210 as previously described. In particular, cutter element carrier 610 has a first end 610a and a second end 610b opposite end 610a. When cutter element assembly 600 is seated in a mating socket 150 in blade 141, 142, first end 610a is positioned forward of and leads second end 610b relative to the cutting direction 106 of bit 100. Accordingly, first end 610a may also be referred to as leading end 610a, and second end 610b may also be referred to as trailing end 610b. Cutter element carrier 610 is generally L-shaped, monolithic member in side view. Similar to cutter element carrier 210, in this embodiment, cutter element carrier 610 includes a base 611 extending from leading end 610a to trailing end 610b and a cutter element support member or block 220 as previously described extending from base 611 at trailing end 610b. As a result, base 611 and support block 220 define a receptacle or pocket 618 extending axially from leading end 610a of cutter element carrier 610 to support block 220. Pocket 618 is sized to receive and mate with cutter element 630.

[0105] Base 611 has a central or longitudinal axis 615, a leading face 611a at end 610a, a trailing face 611b at end 610b, and a radially outer surface 612 extending axially from leading face 611a to trailing face 611b. In this embodiment, leading face 611a and trailing face 611b are defined by planar surfaces oriented perpendicular to axis 615. Outer surface 612 includes a concave cutter element facing surface 613 extending axially (relative to axis 615) from leading face 611a to support block 220, a convex blade facing surface 614 extending axially (relative to axis 615) from leading face 611a to trailing face 611b, and a pair of planar, parallel lateral side surfaces 616 extending axially (relative to axis 615) from leading face 611a to trailing face 611b. Blade facing surface 614 and cutter element facing surface 613 are radially spaced apart (relative to axis 615), and each extends laterally (relative to axis 615) between lateral side surfaces 616. Lateral side surfaces 616 are disposed along opposite lateral sides of surfaces 613, 614, extend generally circumferentially (relative to axis 615) from blade facing surface 614 to cutter element facing surface 613 (along pocket 618), and extend generally circumferentially (relative to axis 615) from blade facing surface 614 to support block 220 (rearward of pocket 618). Surfaces 613, 614, 616 extend parallel to axis 615, and thus, extend perpendicularly from leading face 611a. Cutter element facing surface 613 faces and partially defines pocket 618. In this embodiment, lateral side surfaces 616 are planar surfaces disposed in planes oriented parallel to each other, however, in other embodiments, the lateral side surfaces (e.g., surfaces 216) may not be oriented parallel to each other.

[0106] Similar to cutter element facing surface 213 previously described, in this embodiment, cutter element facing surface 613 is a concave semi-cylindrical surface with a radius of curvature equal the radius of outer cylindrical surface 636 of cutter element 630, and blade facing surface 614 is a convex semi-cylindrical surface. However, unlike cutter element facing surface 213 previously described, in this embodiment, cutter element facing surface 613 does not include concave recess 217, and consequently, cutter element assembly 600 does not include indexing member 219. Outer cylindrical surface 636 of cutter element 630 is seated against, engages, and is fixably secured to mating cutter element facing surface 613 with cutter element 630 rotationally oriented such that planar flats 639 are distal cutter element facing surface 613. Accordingly, semi-cylindrical cutter element facing surface 613 defines a seat for cutter element 630. In this embodiment, a convex rounded transition surface is provided at the intersection between each lateral side surfaces 616 and cutter element facing surface 613.

[0107] Base 611 is sized and shaped to mate and slidingly engage a corresponding socket 150 in a blade 141, 142 with at least a portion of support block 220 (and cutter element 630) extending from socket 150 and cutter supporting 144 of the blade 141, 142. In particular, lateral side surfaces 616 and blade facing surface 614 engage and are fixably secured to mating surfaces defining a corresponding socket 150 in blade 141, 142 to which cutter element assembly 600 is attached.

[0108] Referring still to FIGS. 26 and 27, support block 220 is as previously described. In this embodiment, axis 225 of support block 220 is oriented parallel to axis 615 of base 611. Trailing face 220b of support block 220 is defined by a planar surface that is coplanar and contiguous with trailing face 611b of base 611. Thus, trailing face 611b is disposed in a plane oriented perpendicular to axes 615, 225. Planar surface 637 at trailing end 630b of cutter element 630 is seated flush against the planar surface defining leading face 220a and is fixably secured thereto. In this embodiment, the planar surface defining leading face 220a is oriented perpendicular to axes 615, 225 (i.e., the planar surfaces defining faces 220a, 220b are parallel and oriented perpendicular to axes 615, 225) and axes 225, 635 are coaxially aligned, however, in other embodiments, the planar surface defining the leading face of the support block (e.g., leading face 220a of support block 220) may be oriented at an acute angle relative to a plane oriented perpendicular to the central axis of the support block (e.g., axis 225) to vary the backrake and/or siderake of cutter element 630 when coupled to a blade 141, 142, and as a result the central axis of the support (e.g., central axis 225) and central axis 635 of cutter element 630 are oriented at acute angles relative to each other.

[0109] Outer surface 221 includes a convex semi-cylindrical surface 222 extending axially (relative to axis 225) from leading face 220a to trailing face 220b, and a pair of planar, parallel lateral side surfaces 223 extending axially (relative to axis 225) from leading face 220a to trailing face 220b. Lateral side surfaces 223 are disposed along opposite lateral sides of convex semi-cylindrical surface 222, and extend from convex semi-cylindrical surface 222 to lateral side surfaces 616 of base 611. Each lateral side surface 223 of support block 220 is coplanar and contiguous with a corresponding lateral side surface 616 of base 611. In this embodiment, semi-cylindrical surface 222 of support block 220 has the same radius of curvature as semi-cylindrical surface 614 of base 611, outer cylindrical surface 636 of cutter element 630, and concave cylindrical surface 613 of base 611. A concave round transition surface is provided at the intersection of concave surface 613 of base 611 and leading face 220a of support 220. Base 611 and support block 220 of cutter element carrier 610 are monolithically formed and can generally be made of the same materials as cutter element carrier 210 previously descried.

[0110] Cutter element assembly 600 is generally mounted to a corresponding blade (e.g., blade 141, 142) in the same manner as cutter element assembly 200, however, cutter element assembly 600 is preferably mounted such that a portion of cutting face 633 at or proximal the intersection of bevel 638 and outer surface 636 laterally between planar flats 639 defines a cutting tip and exposure of cutter element 630 of cutter element assembly 600. For purposes of clarity and further explanation, in FIGS. 26 and 27, the portion of cutting face 630 laterally between planar flats 639 that can be positioned to define the cutting tip and exposure of cutter element 630 is labeled with reference numeral 634.

[0111] Referring still to FIGS. 26 and 27, as previously described, in this embodiment, cutter element assembly 600 does not include indexing member 219 and recesses 217, 239 are not provided in surfaces 613, 636 of carrier 610 and cutter element 630, respectively. Rather, in this embodiment, an alternative indexing system is provided. More specifically, leading face 611a includes a plurality of circumferentially-spaced timing marks 617 that designate angular positions measured about central axis 635 when cutter element 630 is seated in pocket 618. In this embedment, timing marks 617 are provided every 5 from a 0 position aligned with a reference plane that contains axes 615, 225, 635 and bisects both carrier 610 and cutter element 630 in half to a +25 position (measured clockwise about axis 635 from the 0 position) and a 25 position (measured counterclockwise about axis 635 from the 0 position). Thus, timing marks 617 define an indexing assembly or system for rotationally indexing and positioning of cutter element 630 when it is seated in pocket 618 (prior to brazing cutter element 630 to carrier 610) to position portion 634 (and associated cutting tip of cutter element 630) at the desired rotational and angular position relative to carrier 610 based on the radial position of cutter element assembly 600 along the corresponding blade 141, 142 and the orientation of cutter element assembly 600 when seated in the corresponding socket 150. For example, in FIG. 27 and as denoted with the dashed line, cutter element 630 is rotationally oriented relative to carrier 610 with portion 634 generally centered relative to the 0 angular position of timing marks 617; whereas in FIG. 28 and as denoted with the dashed line, cutter element 630 is rotationally oriented relative to carrier 610 with portion 634 generally centered relative to the +20 angular position of timing marks 617. Consequently, during assembly of cutter element assembly 600, the rotational position of cutter element 630 relative to carrier 610 can be set prior to brazing by generally aligning and centering portion 634 with the desired rotational angle denoted by timing marks 617.

[0112] Similar to cutter element assembly 200 previously described, cutter element assembly 600 has a generally stadium or obround prismatic shape. More specifically, cutter element assembly 600 has a longitudinal axis 605 generally defined by the longitudinal axis of cutter element carrier 610. In this embodiment, longitudinal axis 605 is intersected by and oriented perpendicular to central axes 615, 225, 635 and oriented parallel to the planar surfaces defining ends 610a, 610b. In addition, in this embodiment, axes 605, 615, 225, 635 lie in a common plane that divides cutter element assembly 600 lengthwise into equal, mirror image halves. In other embodiments, longitudinal axis 605 may be intersected by and oriented perpendicular to central axes 215, 225, but may not intersected by central axis 235. In this embodiment, coplanar surfaces 616, 223 are oriented parallel to axis 605 and convex semi-cylindrical surfaces 614, 222 are intersected by longitudinal axis 615. In this embodiment, surfaces 614, 222 are intersected by longitudinal axis 615 at their respective centers that are furthest from central axes 615, 225.

[0113] As best shown in FIG. 27, cutter element assembly 600 has a maximum length L.sub.600 measured parallel to longitudinal axes 605 (in front view) between convex surfaces 614, 222 of cutter element carrier 610 and measured parallel to longitudinal axes 605 (in front view) between convex surface 614 of cutter element carrier 610 and outer surface 636 of cutter element 630. In addition, cutter element assembly 600 has a maximum width W.sub.600 measured perpendicularly to longitudinal 605, side surfaces 616, and side surfaces 223 from one side surface 616, 223 to the opposite side surface 616, 223, respectively. In this embodiment, the maximum width W.sub.600 is also equal to the outer diameter of cutter element 630. Due to the stadium prismatic shape of cutter element assembly 600, the maximum length L.sub.600 is greater than the maximum width W.sub.600. As previously described, in embodiments described herein, for most drilling applications, the maximum length L.sub.600 of cutter element assembly 600 preferably ranges from 10.0 mm to 30.0 mm, and the maximum width W.sub.600 of cutter element assembly 600 is preferably greater than or equal to 5.0 mm and less than 30.0 mm. In addition, the maximum length L.sub.600 of cutter element assembly 600 is preferably at least 1.25 times the diameter of cutter element 630. In other words, the maximum length L.sub.600 of cutter element assembly 600 is preferably at least 25% greater than the diameter of cutter element 630. In addition, in embodiments described herein, the aspect ratio of cutter element assembly 600 is greater than 1.0 and preferably less than or equal to 2.0.

[0114] As previously described, cutter element assembly 600 can replace one or more cutter element assemblies 200 on bit 100. Each cutter element assembly 600 is generally mounted to a corresponding blade (e.g., blade 141, 142) in the same manner as cutter element assembly 200 with the understanding portion 634 is positioned so as to define the cutting tip of cutter element 630.

[0115] As previously described and shown in FIG. 5, high-aspect ratio cutter element assemblies 200 may be tilted to ensure and/or maintain a desired clearance with each radially adjacent cutter element assembly 200 or cutter element 230. In the embodiments of the high-aspect ratio cutter element assemblies previously described (e.g., cutter element assemblies 200, 300, 400, 500, 600), the planar lateral sides (e.g., planar lateral sides 216, 223, 216, 216, 223, 223, 616) of the base (e.g., 211, 511, 611) and the support block (220, 420, 620) of the cutter element carrier (e.g., cutter element carrier 210, 310, 410, 510, 610) are oriented parallel to each other. However, in other embodiments, the orientation of the planar lateral sides of the cutter element carrier of the high-aspect ratio cutter element assembly can taper toward each other to offer the potential for enhanced clearance with radially adjacent cutter element assemblies and cutter elements without or with reduced tilting. For example, referring now to FIGS. 29 and 30, an embodiment of a tear-drop shaped high-aspect ratio cutter element assembly 700 that can be used in place of one or more high-aspect ratio cutter element assemblies 200 of bit 100 is shown. High-aspect ratio cutter element assembly 700 is substantially the same as high-aspect ratio cutter element 600 previously described with the exception that the lateral sides of the cutter element carrier 710 of high-aspect ratio cutter element assembly 700 are not oriented parallel to teach other, but rather, taper inwardly toward each other. More specifically, cutter element assembly 700 includes cutter element carrier 710 and a cutter element 630 fixably mounted to carrier 710 (e.g., via brazing such as induction brazing). Cutter element 630 is as previously described.

[0116] Cutter element carrier 710 is substantially the same as cutter element carrier 610 previously described. In particular, cutter element carrier 710 has a first end 710a and a second end 710b opposite end 710a. When cutter element assembly 700 is seated in a mating socket in blade 141, 142 (e.g., socket 150), first end 710a is positioned forward of and leads second end 710b relative to the cutting direction 106 of bit 100. Accordingly, first end 710a may also be referred to as leading end 710a, and second end 710b may also be referred to as trailing end 710b. Cutter element carrier 710 is generally L-shaped, monolithic member in side view. Similar to cutter element carrier 610, in this embodiment, cutter element carrier 710 includes a base 711 extending from leading end 710a to trailing end 710b and a cutter element support member or block 720. As a result, base 711 and support block 720 define a receptacle or pocket 718 extending axially from leading end 710a of cutter element carrier 710 to support block 720. Pocket 718 is sized to receive and mate with cutter element 630.

[0117] Base 711 has a central or longitudinal axis 715, a leading face 711a at end 710a, a trailing face 711b at end 710b, and a radially outer surface 712 extending axially from leading face 711a to trailing face 711b. In this embodiment, leading face 711a and trailing face 711b are defined by planar surfaces oriented perpendicular to axis 715. In addition, in this embodiment, leading face 711a includes a plurality of circumferentially-spaced timing marks 617 as previously described that designate angular positions measured about central axis 635 of cutter element 630 when cutter element 630 is seated in pocket 718.

[0118] Outer surface 712 includes a concave cutter element facing surface 713 extending axially (relative to axis 715) from leading face 711a to support block 720, a convex blade facing surface 714 extending axially (relative to axis 715) from leading face 711a to trailing face 711b, and a pair of planar lateral side surfaces 716 extending axially (relative to axis 715) from leading face 711a to trailing face 711b. Blade facing surface 714 and cutter element facing surface 713 are radially spaced apart (relative to axis 715), and each extends laterally (relative to axis 715) between lateral side surfaces 716. Lateral side surfaces 716 are disposed along opposite lateral sides of surfaces 713, 714, extend generally circumferentially (relative to axis 715) from blade facing surface 714 to cutter element facing surface 713 (along pocket 718), and extend generally circumferentially (relative to axis 715) from blade facing surface 714 to support block 720 (rearward of pocket 718). Surfaces 713, 714, 716 extend parallel to axis 715, and thus, extend perpendicularly from leading face 711a. Cutter element facing surface 713 faces and partially defines pocket 718. However, unlike planar lateral side surfaces 616 of base 611 of cutter element carrier 610 previously described, in this embodiment, planar lateral side surfaces 716 are not oriented parallel to each other. Rather, in this embodiment, planar lateral side surfaces 716 slope or taper towards each moving generally circumferentially (relative to axis 715) from cutter element facing surface 713 to blade facing surface 714.

[0119] Similar to cutter element facing surface 613 previously described, in this embodiment, cutter element facing surface 713 is a concave semi-cylindrical surface with a radius of curvature equal the radius of outer cylindrical surface 636 of cutter element 630, and blade facing surface 614 is a convex semi-cylindrical surface. However, unlike blade facing surface 614 previously described, in this embodiment, blade facing surface 714 is disposed at radius of curvature that is less than the radius of curvature of cutter element facing surface 713. Outer cylindrical surface 636 of cutter element 630 is seated against, engages, and is fixably secured to mating cutter element facing surface 713 with cutter element 630 rotationally oriented such that planar flats 639 are distal cutter element facing surface 713. Accordingly, semi-cylindrical cutter element facing surface 713 defines a seat for cutter element 630. In this embodiment, a convex rounded transition surface is provided at the intersection between each lateral side surfaces 716 and cutter element facing surface 713.

[0120] Base 711 is sized and shaped to mate and slidingly engage a corresponding socket in a blade 141, 142 with at least a portion of support block 720 (and cutter element 630) extending from the socket and cutter supporting 144 of the blade 141, 142. In particular, lateral side surfaces 716 and blade facing surface 714 engage and are fixably secured to mating surfaces defining the corresponding socket in blade 141, 142 to which cutter element assembly 700 is attached.

[0121] Referring still to FIGS. 29 and 30, support block 720 is similar to support block 220 previously described. In particular, support block 720 has a central axis 725 oriented parallel to axis 715 of base 711, a leading face 720a defined by a planar surface that is coplanar and contiguous with trailing face 711b of base 710, a trailing face 720b defined by a planar surface that is coplanar and contiguous with trailing face 711b of base 711, and a radially outer surface 721 extending axially (relative to axis 715) from leading face 720a to trailing face 720b. Thus, trailing face 711b is disposed in a plane oriented perpendicular to axes 715, 725. Planar surface 637 at trailing end 630b of cutter element 630 is seated flush against the planar surface defining leading face 720a and is fixably secured thereto. In this embodiment, the planar surface defining leading face 720a is oriented perpendicular to axes 715, 725 (i.e., the planar surfaces defining faces 720a, 720b are parallel and oriented perpendicular to axes 715, 725) and axes 725, 635 are coaxially aligned, however, in other embodiments, the planar surface defining the leading face of the support block (e.g., leading face 720a of support block 720) may be oriented at an acute angle relative to a plane oriented perpendicular to the central axis of the support block (e.g., axis 725) to vary the backrake and/or siderake of cutter element 630 when coupled to a blade 141, 142, and as a result the central axis of the support (e.g., central axis 725) and central axis 635 of cutter element 630 are oriented at acute angles relative to each other.

[0122] Outer surface 721 includes a convex semi-cylindrical surface 722 extending axially (relative to axis 725) from leading face 720a to trailing face 220b, and a pair of planar, parallel lateral side surfaces 723 extending axially (relative to axis 725) from leading face 720a to trailing face 720b. Lateral side surfaces 723 are disposed along opposite lateral sides of convex semi-cylindrical surface 722, and extend from convex semi-cylindrical surface 722 to lateral side surfaces 716 of base 711. Each lateral side surface 723 of support block 720 is coplanar and contiguous with a corresponding lateral side surface 716 of base 711. Thus, planar lateral side surfaces 723 slope or taper toward each other moving circumferentially (relative to axis 725) from convex semi-cylindrical surface 722 to lateral side surface 716 of base 711. In this embodiment, semi-cylindrical surface 722 of support block 720 has the same radius of curvature as outer cylindrical surface 636 of cutter element 630 and concave cylindrical surface 713 of base 711. However, as planar lateral side surfaces 723 slope or taper toward each other moving circumferentially (relative to axis 725) from convex semi-cylindrical surface 722 to lateral side surface 716 of base 711, the radius of curvature of convex semi-cylindrical surface 722 is greater than the radius of curvature of blade facing semi-cylindrical surface 714 of base 711. A concave round transition surface is provided at the intersection of concave surface 713 of base 711 and leading face 720a of support 720. Base 711 and support block 720 of cutter element carrier 710 are monolithically formed and can generally be made of the same materials as cutter element carrier 710 previously descried.

[0123] Cutter element assembly 700 is generally mounted to a corresponding blade (e.g., blade 141, 142) in the same manner as cutter element assembly 600 such that portion 634 of cutting face 633 at or proximal the intersection of bevel 638 and outer surface 636 laterally between planar flats 639 defines a cutting tip and exposure of cutter element 630 of cutter element assembly 700.

[0124] Unlike cutter element assemblies 200, 300, 400, 500, 600 previously described, which have generally stadium prismatic shapes, cutter element assembly 700 has a generally tear drop prismatic shape. More specifically, cutter element assembly 700 has a longitudinal axis 705 generally defined by the longitudinal axis of cutter element carrier 710. In this embodiment, longitudinal axis 705 is intersected by and oriented perpendicular to central axes 715, 725, 635 and oriented parallel to the planar surfaces defining ends 710a, 710b. In addition, in this embodiment, axes 705, 715, 725, 635 lie in a common plane that divides cutter element assembly 700 lengthwise into equal, mirror image halves. In other embodiments, longitudinal axis 705 may be intersected by and oriented perpendicular to central axes 715, 725, but may not intersected by central axis 635. In this embodiment, coplanar surfaces 716, 723 slope toward each other moving from convex semi-cylindrical surface 722 to convex semi-cylindrical surface 714. Convex semi-cylindrical surfaces 714, 722 are intersected by longitudinal axis 715. In this embodiment, surfaces 714, 722 are intersected by longitudinal axis 715 at their respective centers that are furthest from central axes 715, 725.

[0125] As best shown in FIG. 30, cutter element assembly 700 has a maximum length L.sub.700 measured parallel to longitudinal axes 705 (in front view) between convex surfaces 714, 722 of cutter element carrier 710 and measured parallel to longitudinal axes 705 (in front view) between convex surface 714 of cutter element carrier 710 and outer surface 636 of cutter element 630. In addition, cutter element assembly 700 has a maximum width W.sub.700 measured perpendicularly to longitudinal 705 from one side surface 716 to the other side surface 716 at the intersection of convex surface 722 and side surfaces 716. In this embodiment, the maximum width W.sub.700 is also equal to the outer diameter of cutter element 630. Due to the tear drop prismatic shape of cutter element assembly 700, the maximum length L.sub.700 is greater than the maximum width W.sub.700. As previously described, in embodiments described herein, for most drilling applications, the maximum length L.sub.700 of cutter element assembly 700 preferably ranges from 10.0 mm to 30.0 mm, and the maximum width W.sub.700 of cutter element assembly 600 is preferably greater than or equal to 5.0 mm and less than 30.0 mm. In addition, the maximum length L.sub.700 of cutter element assembly 600 is preferably at least 1.25 times the diameter of cutter element 630. In other words, the maximum length L.sub.700 of cutter element assembly 700 is preferably at least 25% greater than the diameter of cutter element 630. In addition, in embodiments described herein, the aspect ratio of cutter element assembly 700 is greater than 1.0 and preferably less than or equal to 2.0.

[0126] As previously described, cutter element assembly 600 can replace one or more cutter element assemblies 200 on bit 100. Each cutter element assembly 700 is generally mounted to a corresponding blade (e.g., blade 141, 142) in the same manner as cutter element assembly 200 with the understanding portion 634 is positioned so as to define the cutting tip of cutter element 630.

[0127] In the embodiment of tear dropped prismatic shaped cutter element assembly 700 shown in FIGS. 29 and 30, cutter element 630 is a shaped cutter element including planar flats 639. However, in general, any suitable cutter element can be mounted to cutter element carrier 610. For example, in FIG. 31, an embodiment of a cutter element assembly 800 including cutter element 230 as previously described mounted to cutter element carrier 710 is shown.

[0128] In the embodiment of drill bit 100 previously described and shown in FIGS. 2, 3, and 5, the minimum distance D.sub.200 between each pair of radially adjacent high-aspect ratio cutter element assemblies 200 on each blade 141, 142 is greater than the minimum distance D.sub.300 between each pair of radially adjacent low-aspect ratio cutter elements 300 on each blade 141, 142. In addition, in the embodiment of drill bit 100 previously described and shown in FIGS. 2, 3, and 5, cutter element assemblies 200 and cutter elements 300 are arranged in a row along the leading side 141a, 142a of each blade 141, 142, respectively, with the radially adjacent high-aspect ratio cutter element assemblies 200 in each row extending radially from proximal the bit axis 105, through cone region 149a, and into shoulder region 149b proximal nose 149d; and the radially adjacent low-aspect ratio cutter elements 300 in each row extending radially from the shoulder region 149b proximal nose 149d, through the remainder of shoulder region 149b to the gage region 149c and the corresponding gage pad 147 of bit 100. However, in other embodiments, the minimum distance D.sub.200 between each pair of radially adjacent high-aspect ratio cutter element assemblies 200 in a row on any one or more blades 141, 142 may be the same or substantially the same as the minimum distance D.sub.300 between each pair of radially adjacent low-aspect ratio cutter elements 300 in the row on the same blade 141, 142 or in a row any other one or more blades 141, 142; and/or the radially adjacent high-aspect ratio cutter element assemblies 200 on one or more blades 141, 142 may extend radially into the shoulder region 149b beyond nose 149d or to gage region 149c.

[0129] 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.