Hybrid bit with truncated cone cutting structure

Abstract

A roller cone for a hybrid drill bit may include a cutter portion extending from a lower surface of the roller cone and a plurality of tungsten carbide inserts ("TCI cutters") embedded into the cutter portion. Each of the plurality of TCI cutters may include a base portion that is configured to be embedded within the cutter portion. The roller cone may further include a truncated portion extending from the cutter portion to a top surface of the roller cone. The truncated portion may have a thickness from an inner surface of the roller cone to an outer surface of the roller cone that is less than a length of the base portion of the TCI cutters.

Description

[0001] HYBRID BIT WITH TRUNCATED CONE CUTTING STRUCTURE

[0002] TECHNICAL FIELD

[0003] This disclosure relates generally to earth-boring drill bits and, more specifically, relates to improved hybrid earth-boring drill bits having a combination of fixed cutters and rolling cutters.

[0004] BACKGROUND

[0005] The success of rotary drilling enabled the discovery7of deep oil and gas reservoirs and production of enormous quantities of oil. The rotary7rock bit was an important invention that made the success of rotary drilling possible. Only soft earthen formations could be penetrated commercially with the earlier drag bit and cable tool, but the two-cone rock bit, invented by7Howard R. Hughes, Sr., U.S. Pat. No. 930,759, drilled the caprock at the Spindietop field near Beaumont, Tex., with relative ease. That venerable invention, within the first decade of the last century, could drill a scant fraction of the depth and speed of the modem rotary rock bit. The onginal Hughes bit drilled for hours; the modem bit now drills for days. Modem bits sometimes drill for thousands of feet instead of merely7a fewfeet. Many advances have contributed to the impressive improvements in rotary7rock bits.

[0006] In drilling boreholes in earthen formations using rolling-cone or rolling-cutter bits, rock bits having one, two, or three rolling cutters rotatably mounted thereon are employed. The bit is secured to the lower end of a drill string that is rotated from the surface or by downhole motors or turbines. The cutters mounted on the bit roll and slide on the bottom of the borehole as the drill string is rotated, thereby engaging and disintegrating the formation material to be removed. The rolling cutters are provided with cutting elements or teeth that are forced to penetrate and gouge the bottom of the borehole by weight from the drill string. The cuttings from the bottom and sides of the borehole are washed aw ay and disposed by drilling fluid that is pumped down from the surface through the hollow7, rotating drill string, and the nozzles as orifices on the drill bit. Eventually the cuttings are carried in suspension in the drilling fluid to the surface up the exterior of the drill string.

[0007] Rolling-cutter bits dominated petroleum drilling for the greater part of the 20th century. With improvements in synthetic diamond technology7that occurred in the 1970s and 1980s, the fixed-blade cutter bit or “drag” bit became popular again in the latter part of the 20th century. Modem fixed-blade cutter bits are often referred to as “diamond” or “PDC” (poly crystalline diamond) cutter bits and are far removed from the original fixed- blade cutter bits of the 19th and early 20th centuries. Diamond or PDC bits carry cutting elements comprising poly crystalline diamond compact layers or ‘'tables” formed on and bonded to a supporting substrate, conventionally of cemented tungsten carbide, the cutting elements being arranged in selected locations on blades or other structures on the bit body with the diamond tables facing generally in the direction of bit rotation. Fixed-blade cutter bits have the advantage of being much more aggressive during drilling and therefore drill much faster at equivalent weight-on-bit levels (WOB) than, for instance, a rolling-cutter bit. In addition, they have no moving parts, which makes their design less complex and more robust.

[0008] The drilling mechanics and dynamics of fixed-blade cutter bits are different from those of rolling-cutter bits precisely because they are more aggressive in cutting and require more torque to rotate during drilling. During a drilling operation, fixed-blade cutter bits are used in a manner similar to that for rolling-cutter bits, the fixed-blade cutter bits also being rotated against a formation being drilled under applied weight-on-bit to remove formation material. The cutting elements on the fixed-blade cutters are continuously engaged as they scrape material from the formation, while in a rolling-cutter bit the cutting elements on each rolling cutter indent the formation intermittently with little or no relative motion (scraping) between the cutting element and the formation.

[0009] A rolling-cutter bit and a fixed-blade cutter bit each have particular applications for which they are more suitable than the other. The much more aggressive fixed-blade cutter bit is superior in drilling in a softer formation to a medium hard formation while the rolling-cutter bit excels in drilling hard formations, abrasive formations, or any combination thereof.

[0010] Hybrid drill bits attempt to combine aspects of both a rolling-cutter bit and a fixed blade cutter bit. To that end, a hybrid drill bit may include a plurality of fixed blades having several polycrystalline diamond cutters. The hybrid drill bit may also have rollingcutters. such as roller cones, which are disposed between the fixed blades of the hybrid drill bit. The roller cones may include several tungsten carbide inserts to engage the formation during drilling.

[0011] Given that hybrid drill bits incorporate features of both rolling-cutter bits and fixed blade cutter bits, packaging all the features into the hybrid drill bit may be challenging, especially in applications calling for smaller diameter drill bits, such as drill bits having diameters less than 10 inches. For example, bearings supporting the roller cones on a hybrid drill bit may not be scaled down indefinitely, but must maintain a sufficient size to have sufficient strength to support the roller cones. The size of the roller cones may similarly be constrained based at least on the size of the bearings.

[0012] SUMMARY

[0013] In accordance with some embodiments of the disclosure, a roller cone for a hybrid drill bit may include a cutter portion extending from a lower surface of the roller cone and a plurality of tungsten carbide inserts (“TCI cutters”) embedded into the cutter portion. Each of the plurality of TCI cutters may include a base portion that is configured to be embedded within the cutter portion. The roller cone may further include a truncated portion extending from the cutter portion to a top surface of the roller cone. The truncated portion may have a thickness from an inner surface of the roller cone to an outer surface of the roller cone that is less than a length of the base portion of the TCI cutters.

[0014] In some embodiments, a hybrid drill bit may include a drill bit body having a diameter of 10 inches or less, a plurality of blades extending from a central portion of the drill bit body, and a plurality of poly crystalline diamond cutters (“PDC cutters”) embedded into each of the plurality of blades. The hybrid drill bit may further include a fluid delivery' conduit disposed toward a center of drill bit body. A roller cone may be disposed between two blades of the plurality of blades. The roller cone may comprise a cutter portion extending from a lower surface of the roller cone, a plurality of tungsten carbide inserts (“TCI cutters”) embedded into the cutter portion, and a truncated portion extending from the cutter portion to a top surface of the roller cone.

[0015] In some embodiments, a roller cone for a hybrid drill bit, may include a cutter portion extending from a lower surface of the roller cone, a plurality of tungsten carbide inserts embedded into the cutter portion, and a truncated portion extending from the cutter portion to a top surface of the roller cone.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 shows a perspective view of an exemplary hybrid drill bit.

[0018] FIG. 2 shows a wire-frame profile view of an exemplary' roller cone of the hybrid drill bit shown in FIG. 1. FIG. 3 shows a top view of a hybrid drill bit according to one example of the disclosure.

[0019] FIG. 4 shows a perspective view of the hybrid drill bit of FIG. 3.

[0020] FIG. 5 shows a wire-frame profile view of a roller cone of the hybrid drill bit shown in FIG. 3.

[0021] FIG. 6 shows a wire-frame view of an exemplary roller cone and bearing.

[0022] The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views.

[0023] DETAILED DESCRIPTION

[0024] FIG. 1 shows a perspective view' of an exemplary hybrid drill bit. In FIG. 1, a hybrid drill bit 100 may comprise a drill bit body 102 comprising one or more blades 104 extending from a central portion of the drill bit body 102. The blades 104 may be configured to support several polycrystalline diamond cutters ( PDC cutters”) 108. The hybrid drill bit 100 may further comprise one or more roller cones 110 disposed in cone pockets 106 formed between the blades 104 in the drill bit body 102. The roller cones 110 may be configured to support several tungsten carbide insert cutters (“TCI cutters”) 112. Upon rotation of the hybrid drill bit 100, the PDC cutters 108 may be configured to shear or scrape material from a formation, while the TCI cutters 112 may be configured to penetrate and gouge the formation.

[0025] FIG. 2 shows a wire-frame profile view of an exemplary roller cone of the hybrid drill bit shown in FIG. 1. In FIG. 2, the roller cone 110 comprises a bottom surface 116 and a top surface 118 that is substantially parallel to the bottom surface 116. The roller cone 110 may comprise an outer surface 120 that extends from the bottom surface 116 to the top surface 1 18. The outer surface 120 is formed in a generally conical shape and is configured to house the TCI cutters 112 at various positions along the outer surface 120. The roller cone 110 is rotationally supported by a bearing 150 comprising a bearing surface 152. The bearing 150 is configured to support the roller cone 110 against the stresses experienced during operation and to allow the roller cone 1 10 to rotate during operation. As a diameter of the drill bit body 102 decreases, the bearings 150 supporting the roller cones 110 on the hybrid drill bit 100 may not be scaled down indefinitely. Rather, the bearings 150 must maintain a sufficient size to have sufficient strength to support the roller cones 110. The size of the roller cones 110 may similarly be constrained based at least on the size of the bearings 150.

[0026] As shown in FIG. 2, the outer surface 120 of the roller cone 1 10 is formed such that there is sufficient thickness in the roller cone 110 to allow the insertion of the TCI cutters 112 along the length of the outer surface 120. That is, the outer surface 120 of the roller cone 110 is such that a thickness of the roller cone 110 between the outer surface 120 and the bearing 150 is greater than a length of a base portion 113 of the TCI cutter 112 (i.e., a greater than a length of the portion of the TCI cutter 1 12 that is embedded within the roller cone 110).

[0027] When hybrid drill bits such as drill bit 100 are formed having relatively small diameters (e.g., diameters of about 10 inches or less, diameters of about 8 and % inches or less, or diameters of 6 and % inches or less) it may be difficult to package the hybrid drill bit to maintain efficient drilling. For example, in FIG. 1 the hybrid drill bit 100 is shown with three blades 104. However, in order to fit the roller cones 110 between the blades 104, only two of the blades 104 comprise PDC cutters 108 that extend into the center of hybrid drill bit 100. Accordingly, toward the center of the hybrid drill bit 100. there are fewer PDC cutters 108 than at distances away from the center of the hybrid drill bit 100, which may result in uneven or increased wear on the PDC cutters 108. Furthermore, the hybrid drill bit 100 may comprise a fluid delivery' conduit 114 that is operable to deliver fluid to the end of the drill pipe to provide cooling to the PDC cutters 108 and the TCI cutters 112 or to help clear material loosened by the hybrid drill bit 100. In smaller diameter hybrid drill bits, such as the hybrid drill bit 100, the fluid delivery conduit 114 may be disposed tow ard an outside of the hybrid drill bit 100. This may result in relatively inefficient cooling or cleaning near the center of the hybrid drill bit 100.

[0028] FIG. 3 shows a top view of a hybrid drill bit according to one example of the disclosure, FIG. 4 shows a perspective view of the hybrid drill bit of FIG. 3, and FIG. 5 shows a wire-frame profile view of a roller cone of the hybrid drill bit show n in FIG. 3. In FIGS. 3-5, a hybrid drill bit 200 is provided that may increase drilling efficiency even at relatively small diameters (e.g., diameters of about 10 inches or less). The hybrid drill bit 100 may comprise a drill bit body 202 comprising one or more blades 204 extending from a central portion of the drill bit body 202. The blades 204 may be configured to support several PDC cutters 208. The hybrid drill bit 200 may further comprise one or more roller cones 210 disposed in cone pockets 206 formed between the blades 204 in the drill bit body 202. The roller cones 210 may be configured to support several TCI cutters 212.

[0029] As shown in FIGS. 4 and 5, the PDC cutters 208 may extend from a center of the drill bit body 202 on each of the blades 204. For example, on each of the blades 204, PDC cutters 208 may be disposed at about equal distances from the center of the drill bit body 202 beginning at a position relatively close to the center of the drill bit body 202 and extending outward therefrom. In some embodiments, each of the blades 204 may have a similar number of PDC cutters 208 even when the hybrid drill bit 200 has a relatively small diameter. This may be facilitated by modifications to roller cones 210, as will be described in more detail below.

[0030] In FIGS. 3-5. the roller cone 210 may comprise a bottom surface 216, a top surface 218, and an outer surface 220 extending between the bottom surface 216 and the top surface 218. As mentioned above, the roller cone 210 may comprise a plurality of TCI cutters 212. The TCI cutters 212 may be arranged in several circumferential rows along the outer surface 220. For example, the roller cone 210 may comprise TCI cutters 212 in a first circumferential row 212a (e.g., an outermost row or gage row), a second circumferential row 212b (e.g., a heel row) a third circumferential row 212c (e.g., an adjacent heel row), and a fourth circumferential row 212d (e.g., an inner row).

[0031] The first circumferential row 212a or gage row may be configured to interface with a sidewall of the borehole and may protect the drill bit 200 from abrasive wear resulting from contact with the sidewall. The second circumference row 212b or heel row may be configured to engage with the borehole at an intersection of the sidewall of the borehole and a bottom surface of the borehole. The third and fourth circumferential rows 212c, 212d may be configured to engage with the bottom surface of the borehole. The TCI cutters 212 on the second, third, and fourth circumferential rows 212b, 212c, 212d may thus be referred to as bottom-surface interfacing TCI cutters.

[0032] The first, second, third, and fourth circumferential rows 212a-212d of TCI cutters 212 may be disposed on various portions of the outer surface 220 of the roller cone 210. For example, the first circumferential row 212a of TCI cutters 212 may be on a bottom expanding portion 222 of the outer surface (e.g., a portion of the outer surface 220 where a diameter of the roller cone 210 increases from the bottom surface 216 toward the top surface 218 or a gage portion). The second circumferential row 212b of TCI cutters 212 may be on a second expanding portion 224 of the outer surface 220 (e.g.. a heel portion). The fourth circumferential row 212d of TCI cutters may be on a first frustoconical portion 226 of the outer surface 220 (e.g., a portion of the outer surface 220 where a diameter of the roller cone 210 decreases from the bottom surface 216 toward the top surface 218). The third circumferential row 212c may be on the outer surface 220 at a transition between the second expanding portion 224 and the first frustoconical portion 226. The placement of the rows 212a-212d of TCI cutters 212 described herein are exemplary and other configurations may also be possible.

[0033] Each of the TCI cutters 212 are embedded within the roller cone 210. Accordingly, each of the TCI cutters 212 comprises a base portion 213 that is configured to be embedded within the roller cone 210. The roller cone 210 may comprise a cutter portion 227 in which the TCI cutters 212 are embedded on the roller cone 210. The cutter portion 227 may thus include the bottom expanding portion 222, the second expanding portion 224, and the first frustoconical portion 226 of the outer surface 220. The cutter portion 227 may be a portion of the roller cone 210 that has a thickness from an inner surface 219 of the roller cone 210 to the outer surface 220 that is greater than a length of the base portion 213 of the TCI cutters 212 such that the TCI cutters 212 may be securely embedded within the cutter portion 227. In some embodiments, the cutter portion 227 of the roller cone 210 may extend from the bottom surface 216 toward the top surface 218 for one-half a height (e.g., a distance betw een the bottom surface 216 and the top surface 218) of the roller cone 210. In some embodiments, the cutter portion 227 may extend two-thirds or three-fourths the height of the roller cone 210 from the bottom surface 216 toward the top surface 218.

[0034] The rows 212a-212d of TCI cutters 212 described above may be disposed in the cutter portion 227 of the roller cone 210. How ever, the TCI cutters 212 are not limited to being disposed in circumferential rows. The TCI cutters 212 may be longitudinally offset from one another within the cutter portion 227 of the roller cone 210, or may be disposed randomly throughout the cutter portion 227 of the roller cone 210.

[0035] The roller cone 210 may further comprise a truncated portion 229. The truncated portion 229 may be a top portion (e.g., a portion closest to the top surface 218 as shown in FIG. 5) in which no TCI cutters 212 are embedded in the roller cone. The truncated portion 227 may comprise from about one-fourth to one half of the height of the roller cone extending from the top surface 218 toward the bottom surface 216. The truncated portion may comprise a thickness from the inner surface 219 of the roller cone 210 to the outer surface 220 that is less than a length of the base portion 213 of the TCI cutters 212 (e.g., a thickness that is less than a length of the base portion 213 of the TCI cutters 212 excluding the first circumferential row 212a of TCI cutters 212 on a bottom expanding portion 222).

[0036] The outer surface 220 along the truncated portion 229 may comprise a second frustoconical portion 230 that is inset from the first frustoconical portion 226 via a stepped portion 228. The stepped portion 228 may comprise a portion of the outer surface 220 that rapidly decreases in diameter in a direction from the bottom surface 216 toward the top surface 218. For example, the stepped portion 228 may have a frustoconical shape with a slant angle a of about 20° or less. In some embodiments, the slant angle a may be about 15° or less. In some embodiments, the stepped portion 228 may be substantially parallel to the top surface 218 and the bottom surface 216 (e.g., the slant angle a may be about 0°).

[0037] In some embodiments, a slant angle P of the second frustoconical portion 230 may be similar or substantially similar to a slant angle 0 of the first frustoconical portion 226. In some embodiments, the slant angle of the second frustoconical portion 230 may be within 10° of the slant angle 0 of the first frustoconical portion 226. While the various portions 222. 224. 226, 228. 230 of the outer surface 220 of the roller cone 210 are shown as being substantially conical (e g., frustoconical) in shape, the roller cone 210 is not limited to shapes shown in FIGS. 3-5. In some examples, the portions 222, 224, 226, 228, 230 of the outer surface 220 may comprise other shapes such as cylindrical shapes, partial spherical shapes, or any other angular swept or curved swept shape.

[0038] The truncated portion 229 provides for a relatively small volume while still sitting on the bearing surface 152 of the bearing 150. For example, as compared to roller cone 110, the roller cone 210 may comprise a substantially smaller volume. Accordingly, the hybrid drill bit 200 may be constructed such that each of the blades 204 may comprise PDC cutters 208 along the entire length of the blade 204, including at or near a center axis of the hybrid drill bit 200. For example, the cone pocket 206 of the hybrid drill bit 200 may be formed in the drill bit body 202 to have a surface that substantially follows the outer surface of the cutter portion 227 and the truncated portion 229 of the roller cone 210. Because the cone pocket 206 follows the outer surface of the roller cone 210, the drill bit body 202 may include more volume to accommodate the PDC cutters 208 along the entire length of the blade 204. This can prevent wear on the PDC cutters 208 because there are a similar number of PDC cutters 208 similarly spaced along each of the blades 204, even when the diameter of the hybrid drill bit is relatively small (e.g., about 10 inches or less). In some embodiments, the hybrid drill bit 200 may comprise a fluid delivery conduit 214. With the roller cones 210 having the truncated portion 229 on the hybrid drill bit 200, and with the cone pockets 206 being formed to follow the outer surface of the roller cones 210, the fluid delivery conduit 214 may be disposed toward the center of the hybrid drill bit 200. In some embodiments, the fluid delivery conduit 214 may be disposed to be at or within about one-half of the radius of the drill bit body 202 of the hybrid drill bit 200. Thus, by utilizing the roller cones 210 with the truncated portion 229. the fluid delivery conduit 214 can deliver fluid, such as cooling fluid and / or lubricating fluid toward the center of the hybrid drill bit, even when the diameter of the hybrid drill bit 200 is relatively small (e.g., about 10 inches or less).

[0039] FIG. 6 shows a wire-frame view of an exemplary roller cone and bearing. In some embodiments, the roller cone 210 may be configured to minimize a difference in roll ratios among the various rows 212a-212d of TCI cutters 212 across the roller cone 210. By minimizing the difference in roll ratios, the roller cone 210 may operate closer to a true rolling cone where sliding action of the roller cone 210 is reduced, which reduces wear on the roller cone.

[0040] At any given point in the rotation of the roller cone 210 during drilling, there may be one of the TCI cutters 212 that operates as a driving compact while others of the TCI cutters are being driven or sliding. With the roller cone 210 comprising the truncated portion 229, the difference between roll ratios of the rows 212a-212d of TCI cutters 212 may be reduced while maintaining an optical cutting structure for the PDC cutters 208 (see FIGS. 3 and 4).

[0041] The roll ratio of a position on the roller cone 210 may be defined as the ratio of a distance of rotation of the position (e.g.. the position corresponding to the distal end of one of the TCI cutters 212) about the drill bit axis 234 (e.g., a distance of the rotation of the position corresponding to the distal end of one of the TCE cutters 212 about the drill bit axis 234) as compared to a distance of rotation of the position about the roller cone axis 232 (e.g., a distance of the rotation of the position corresponding to a distal end of one of the TCI cutters 212 about the roller cone axis 232). For example, the roll ratio for a distal end of a given cutter 212 may be determined as follows:

[0042] Circumference of rotation about drill bit axis Roll Ratio "RR' = - -f - -ri - - - - -

[0043] Circumference of rotation about roller cone axis As applied to the roller cone 210, the roll ratio of the second circumferential row 212b of TCI cutters 212 mav be expressed as RR =22n7rrrdcl6the roll ratio for the third circumferential row 212c of TCI cutters 212 may be expressed as RR =2m dcand the roll ratio of the fourth circumferential row 212d (the inner most row shown in the exemplary roller cone 210) of TCI cutters 212 may be expressed as RR — With the roller cone 210 comprising the cutter portion 227 with TCI cutters 212 and the truncated portion 229 with no TCI cutters 212, the roller cone 210 may be configured such that the roll ratios of the bottom-surface interfacing TCI cutters (e.g. the TCI cutters 212 of the second, third, and fourth circumferential rows 212b, 212c, 212d and excluding the gage row 212a) may be between 1.50 and 2.50. In some embodiments, a maximum difference in roll ratios among the bottom-surface interfacing TCI cutters may be about 1 or less. In some embodiments, the maximum difference between roll ratios of the bottom-surface interfacing TCI cutters may be 0.250 or less (e.g.. a difference between a maximum roll ratio of the TCI cutters 212 and a minimum roll ratio of the TCI cutters (excluding, e.g., sidewall engaging TCI cutters 212 on a gage row) may be 0.250 or less). Such roll ratios of the TCI cutters 212 may help to reduce wear in the TCI cutters 212 over time, such as in highly abrasive applications.

[0044] It is again noted that in some embodiments, the TCI cutters 212 may be configured at different longitudinal positions throughout the cutter portion 227 and may not be disposed in circumferential rows as shown. Such TCI cutters 212 may comprise gage cutters configured to interface with a sidewall of the borehole, heel cutters configured to engage with the borehole at an intersection of the sidewall and the bottom surface of the borehole and cutters configured to engage with the borehole at the bottom surface of the borehole. The TCI cutters 212 excluding the gage cutters may be referred to as bottomsurface interfacing TCI cutters. In some embodiments, the maximum difference of roll ratios of the bottom-surface interfacing TCI cutters may be about 1 or less, or may be about 0.250 or less. In some embodiments, the maximum difference of roll ratios of the TCI cutters 212 on the frustoconical portion 226 (e.g., a portion of the outer surface 220 where a diameter of the roller cone 210 decreases from the bottom surface 216 toward the top surface 218) may be about 1 or less, or may be about 0.250 or less.

[0045] While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the disclosure. In addition, the various features, elements, and embodiments described herein may be claimed or combined in any combination or arrangement.

Claims

CLAIMSWhat is claimed is:

1. A roller cone for a hybrid drill bit, the roller cone comprising: a cutter portion extending from a lower surface of the roller cone; a plurality of tungsten carbide inserts (“TCI cutters’") embedded into the cutter portion, each of the plurality of TCI cutters comprising a base portion that is configured to be embedded within the cutter portion; and a truncated portion extending from the cutter portion to a top surface of the roller cone, the truncated portion having a thickness from an inner surface of the roller cone to an outer surface of the roller cone that is less than a length of the base portion of the TCI cutters.

2. The roller cone of claim 1, wherein the truncated portion is a portion of the roller cone in which no TCI cutters are embedded in the roller cone.

3. The roller cone of claim 1, further comprising a stepped portion between the cutter portion and the truncated portion, wherein an outer surface of the cutter profile has a first frustoconical shape, an outer surface of the truncated portion has a second frustoconical shape, and the stepped portion has a third frustoconical shape.

4. The roller cone of claim 3, wherein the third frustoconical shape of the stepped portion comprises a slant angle of 20° or less.

5. The roller cone of claim 3, wherein a slant angle of the second frustoconical shape is substantially similar to a slant angle of the first frustoconical shape.

6. A hybrid drill bit comprising: a drill bit body; a plurality of blades extending from a central portion of the drill bit body; a plurality of cone pockets formed into the drill bit body between the plurality of blades; a plurality of polycrystalline diamond cutters (“PDC cutters”) embedded into each of the plurality of blades; and a roller cone according to claim 1 disposed in each of the plurality of cone pockets.

7. The hybrid drill bit of claim 6, wherein a diameter of the drill bit body is 10 inches or less.

8. The hybrid drill bit of claim 7, wherein the plurality of cone pockets comprises a surface that substantially follows an outer surface of the cutter portion and the truncated portion of the roller cone, and wherein the hybrid drill bit further comprises a fluid delivery’ conduit disposed toward a center of drill bit body.

9. The hybrid drill bit of claim 8, wherein the fluid delivery conduit is a distance from a center axis of the drill bit body, the distance being equal to or less than half of a radius of the drill bit body.

10. A hybrid drill bit comprising: a drill bit body having a diameter of 10 inches or less; a plurality’ of blades extending from a central portion of the drill bit body; a plurality of poly crystalline diamond cutters (“PDC cutters”) embedded into each of the plurality of blades; a plurality of cone pockets formed into the drill bit body between the plurality of blades; a fluid delivery conduit disposed toward a center of drill bit body; and a roller cone disposed in each of the plurality of cone pockets, the roller cone comprising: a cutter portion extending from a lower surface of the roller cone; a plurality of tungsten carbide inserts (“TCI cutters”) embedded into the cutter portion; and a truncated portion extending from the cutter portion to a top surface of the roller cone.

11. The hybrid drill bit of claim 10, wherein the plurality of cone pockets comprises a surface that substantially follows an outer surface of the cutter portion and the truncated portion of the roller cone, and wherein the fluid delivery conduit is a distance from a center axis of the drill bit body, the distance being equal to or less than half of a radius of the drill bit body.

12. The hybrid drill bit of claim 10, wherein the roller cone further comprises further comprising a stepped portion between the cutter portion and the truncated portion, wherein an outer surface of the cutter portion has a first frustoconical shape, an outer surface of the truncated portion has a second frustoconical shape, and the stepped portion has a third frustoconical shape.

13. The hybrid drill bit of claim 12, wherein the third frustoconical shape of the stepped portion comprises a slant angle of 20° or less.

14. The hybrid drill bit of claim 12, wherein a slant angle of the second frustoconical shape is substantially similar to a slant angle of the first frustoconical shape.

15. The hybrid drill bit of claim 10, wherein each of the plurality of TCI cutters comprises a base portion configured to be embedded within the cutter portion, and wherein the truncated portion comprises a thickness from an inner surface to an outer surface that is less than a length of the base portion of the TCI cutters.

16. A roller cone for a hybrid drill bit, the roller cone comprising: a cutter portion extending from a lower surface of the roller cone; a plurality of TCI cutters embedded into the cutter portion; and a truncated portion extending from the cutter portion to a top surface of the roller cone.

17. The roller cone of claim 1 , further comprising further comprising a stepped portion between the cutter portion and the truncated portion, wherein an outer surface of the cutter profile has a first frustoconical shape, an outer surface of the truncated portion has a second frustoconical shape, and the stepped portion has a third frustoconical shape,wherein the third frustoconical shape of the stepped portion comprises a slant angle of 20° or less.

18. The roller cone of claim 17, wherein a slant angle of the second frustoconical shape is substantially similar to a slant angle of the first frustoconical shape.

19. The roller cone of claim 16, wherein each of the plurality of TCI cutters comprise a base portion configured to be embedded within the cutter portion, and wherein the truncated portion comprises a thickness from an inner surface to an outer surface that is less than a length of the base portion of the TCI cutters.

20. The roller cone of claim 16, wherein the truncated portion is a portion of the roller cone in which no TCI cutters are embedded in the roller cone.

21. The roller cone of claim 16, wherein a maximum difference in roll ratios of bottom-surface interfacing TCI cutters of the TCI cutters is about 0.250 or less.

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