Patent Publication Number: US-2022220807-A1

Title: Hybrid bit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of, and priority to, U.S. Patent Application No. 62/850,619 filed on May 21, 2019, which is incorporated herein by this reference in its entirety. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     Downhole bits include two categories: fixed bits, or “drag” bits, and rotary bits. Fixed bits include fixed cutting structures that do not move relative to the bit as the bit rotates. Rotary bits include one or more rotary cutting structures that rotate relative to the bit as the bit rotates. Hybrid bits include some aspect of both fixed bits and rotary bits. 
     SUMMARY 
     In some aspects, a bit includes a wheel-shaped rolling cutting structure that includes a plurality of cutting elements located on a radially outer surface of the bit. 
     In other aspects, a hybrid bit includes one or more fixed cutting structures and one or more rolling cutting structures, the rolling cutting structures including a plurality of conical cutting elements. The rolling cutting structures may be conical or non-conical. 
     In yet other embodiments, a kit for drilling includes a conical or non-conical rolling cutting structure having cutting elements located on a radially outward surface of the rolling cutting structure. The kit may include a plurality of sleeves, each sleeve being configured to adjust a height of the rolling cutting structure. 
     This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
     Additional features and advantages of embodiments of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of such embodiments. The features and advantages of such embodiments may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features will become more fully apparent from the following description and appended claims, or may be learned by the practice of such embodiments as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other features of the disclosure can be obtained, a more particular description will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. For better understanding, the like elements have been designated by like reference numbers throughout the various accompanying figures. While some of the drawings may be schematic or exaggerated representations of concepts, at least some of the drawings may be drawn to scale. Understanding that the drawings depict some example embodiments, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  is a representation of a drilling system, according to at least one embodiment of the present disclosure; 
         FIG. 2-1  is a perspective view of a rolling cutting structure, according to at least one embodiment of the present disclosure; 
         FIG. 2-2  is a cross-sectional view of the rolling cutting structure of  FIG. 2-1 , according to at least one embodiment of the present disclosure; 
         FIG. 3-1  is a perspective view of a bit, according to at least one embodiment of the present disclosure; 
         FIG. 3-2  is a bottom view of the bit of  FIG. 3-1 , according to at least one embodiment of the present disclosure; 
         FIG. 3-3  is a cross-sectional view of the bit of  FIG. 3-1 , according to at least one embodiment of the present disclosure; 
         FIG. 3-4  is a cutting element profile of the bit of  FIG. 3-1 , according to at least one embodiment of the present disclosure; 
         FIG. 3-5  is another cross-sectional view of the bit of  FIG. 3-1 , according to at least one embodiment of the present disclosure; 
         FIG. 4  is a perspective view of a sleeve, according to at least one embodiment of the present disclosure; 
         FIG. 5-1  is a perspective view of a bit, according to at least one embodiment of the present disclosure; 
         FIG. 5-2  is a bottom view of the bit of  FIG. 5-1 , according to at least one embodiment of the present disclosure; 
         FIG. 5-3  is a side view of the bit of  FIG. 5-1 , according to at least one embodiment of the present disclosure; 
         FIG. 6  is a bottom view of a bit, according to at least one embodiment of the present disclosure; 
         FIG. 7-1  is a perspective view of a bit, according to at least one embodiment of the present disclosure; 
         FIG. 7-2  is a bottom view of the bit of  FIG. 7-1 , according to at least one embodiment of the present disclosure; 
         FIG. 7-3  is a cross-sectional view of the bit of  FIG. 7-1 , according to at least one embodiment of the present disclosure; 
         FIG. 7-4  is another cross-sectional view of the bit of  FIG. 7-1 , according to at least one embodiment of the present disclosure; 
         FIG. 7-5  is a cutting profile of the bit of  FIG. 7-1 , according to at least one embodiment of the present disclosure; and 
         FIG. 8  is a method chart, according to at least one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure generally relates to devices, systems, and methods for drill bits including cutting elements.  FIG. 1  shows one example of a drilling system  100  for drilling an earth formation  101  to form a wellbore  102 . The drilling system  100  includes a drill rig  103  used to turn a drilling tool assembly  104  which extends downward into the wellbore  102 . The drilling tool assembly  104  may include a drill string  105 , a bottomhole assembly (“BHA”)  106 , and a bit  110 , attached to the downhole end of drill string  105 . 
     The drill string  105  may include several joints of drill pipe  108  connected end-to-end through tool joints  109 . The drill string  105  transmits drilling fluid through a central bore and transmits rotational power from the drill rig  103  to the BHA  106 . In some embodiments, the drill string  105  may further include additional components such as subs, pup joints, etc. The drill pipe  108  provides a hydraulic passage through which drilling fluid is pumped from the surface. The drilling fluid discharges through selected-size nozzles, jets, or other orifices in the bit  110  for the purposes of cooling the bit  110  and cutting structures thereon, cleaning the bit  110  and cutting structures thereon of any cuttings, swarf, or other material that may have accumulated on the bit  110  and/or the cutting structures, and for lifting cuttings out of the wellbore  102  as it is being drilled. 
     The BHA  106  may include the bit  110  or other components. An example BHA  106  may include additional or other components (e.g., coupled between to the drill string  105  and the bit  110 ). Examples of additional BHA components include drill collars, stabilizers, measurement-while-drilling (“MWD”) tools, logging-while-drilling (“LWD”) tools, downhole motors, underreamers, section mills, hydraulic disconnects, jars, vibration or dampening tools, steering tools, other components, or combinations of the foregoing. 
     In general, the drilling system  100  may include other drilling components and accessories, such as special valves (e.g., kelly cocks, blowout preventers, and safety valves). Additional components included in the drilling system  100  may be considered a part of the drilling tool assembly  104 , the drill string  105 , or a part of the BHA  106  depending on their locations in the drilling system  100 . 
     The bit  110  in the BHA  106  may be any type of bit suitable for degrading downhole materials. For instance, the bit  110  may be a drill bit suitable for drilling the earth formation  101 . Example types of drill bits used for drilling earth formations are fixed-cutter or drag bits. In other embodiments, the bit  110  may be a mill used for removing metal, composite, elastomer, other materials downhole, or combinations thereof. For instance, the bit  110  may be used with a whipstock to mill into casing  107  lining the wellbore  102 . The bit  110  may also be a junk mill used to mill away tools, plugs, cement, other materials within the wellbore  102 , or combinations thereof. Swarf or other cuttings formed by use of a mill may be lifted to surface, or may be allowed to fall downhole. 
       FIG. 2-1  is a perspective view of a rolling cutting structure  212 , according to at least one embodiment of the present disclosure. In some embodiments, the rolling cutting structure  212  may be wheel-shaped, or generally wheel-shaped. The rolling cutting structure  212  has an outer surface  214 . A plurality of cutting elements  216  may be attached to the outer surface  214  or inserted into a pocket in the outer surface  214 . For example, the plurality of cutting elements  216  may be attached to the rolling cutting structure  212  using any method, including braze, weld, mechanical fastener, press-fit, interference fit, or any other type of connection. 
     In some embodiments, a hard material forms the cutting element  216  or a substrate thereof. Substrates according to embodiments of the present disclosure may be formed of cemented carbides, such as tungsten carbide, titanium carbide, chromium carbide, niobium carbide, tantalum carbide, vanadium carbide, or combinations thereof cemented with iron, nickel, cobalt, or alloys thereof. For example, a substrate may be formed of cobalt-cemented tungsten carbide. Ultrahard layers according to embodiments of the present disclosure may be formed of, for example, polycrystalline diamond, such as formed of diamond crystals bonded together by a metal catalyst such as cobalt or other Group VIII metals under sufficiently high pressure and high temperatures (sintering under HPHT conditions), thermally stable polycrystalline diamond (polycrystalline diamond having at least some or substantially all of the catalyst material removed), or cubic boron nitride. Further, it is also within the scope of the present disclosure that the ultrahard layer may be formed from one or more layers, Which may have a gradient or stepped transition of diamond content therein. In such embodiments, one or more transition layers (as well as the other layer) may include metal carbide particles therein. Further, when such transition layers are used, the combined transition layers and outer layer may collectively be referred to as the ultrahard layer, as that term has been used in the present application. That is, the interface surface on which the ultrahard layer (or plurality of layers including an ultrahard material) may be formed is that of the cemented carbide substrate. 
     In some embodiments, the cutting elements  216  may be conical or frustoconical in shape. In other embodiments, the cutting elements  216  may have an outer surface that is convex or concave. In still other embodiments, the cutting elements  216  may have an outer surface that has multiple taper angles, multiple radii of curvature, different concavities, at least one straight and at least one curved section, any other cutting element geometry, or combinations thereof. The cutting elements  216  may have non-planar surfaces that are directed radially outward from the outer surface  214 . In yet other embodiments, the cutting elements  216  may be apexed, pointed, ridged, or have any other shape. In further embodiments, the cutting elements may be a cross-sectional shape including one or more of round (e.g., circular, ellipsoidal), polygonal (e.g., hexagonal, pentagonal, square, or polygon of any side), or non-polygonal (e.g., straight and curved edges). In some embodiments, the cutting elements  216  may be radially symmetrical. The cutting elements  216  may include one, two, three, four, five, six, or more planes of symmetry. In other embodiments, the cutting elements  216  may be asymmetric, or include no plane of symmetry. In the same or other embodiments, the cutting elements may have a non-symmetric three-dimensional shape, including points that are located away from the longitudinal axis of the cutting elements. The cutting elements  216  may include diamond, such as polycrystalline diamond, or may be any suitable cutting element. 
     As noted above, the plurality of cutting elements  216  may be attached to the outer surface  214  or inserted into a pocket in the outer surface  214 . In some embodiments, the cutting elements  216  only extend from the outer surface  214  of the rolling cutting structure  212  in the radial direction and do not extend from a leading face or trailing face of the rolling cutting structure  212 . In some embodiments, each cutting element  216  has a respective cutting element axis  215  that generally extends through a center of the substrate of the cutting element  216  and a center of a cutting face of the cutting element. The cutting element axes  215  may extend radially from the outer surface  214  of the rolling cutting structure  212 . In some embodiments, the cutting element axes  215  of one or more rows may be perpendicular to an axis  213  (e.g., journal axis) of the rolling cutting structure  212 . Due to the shape and profile of the outer surface  214 , the angle between the cutting element axis and the outer surface  214  where the cutting element is attached may be different than the angle between the cutting element axis and the axis  213  of the rolling cutting structure  212 . 
     Although wheels are generally described through the specification with regard to the rotating cutting structure  212 , in some embodiments, the wheels are cone or truncated cone rolling cutting structures. 
     In some embodiments, the rolling cutting structure  212  may include one or more rows of cutting elements  216 . A first row (e.g., leading row) of cutting elements  216  may include one or more primary cutting elements  216 , and a second row (e.g., trailing row) of cutting elements may include one or more secondary cutting elements  217  attached to the outer surface  214  of the rolling cutting structure  212 . The primary and secondary cutting elements  216 ,  217  may be diamond inserts, or may be any cutting element used in downhole drilling. In some embodiments, the rolling cutting structure  212  may only include the cutting elements  216 , without the secondary cutting elements  217 . In some embodiments, at least 50 percent of the cutting elements have an ultrahard coating. In some embodiments, at least 90 percent of the cutting elements have an ultrahard coating. In some embodiments, all of the cutting elements have an ultrahard coating. 
     In some embodiments, the rolling cutting structure  212  may include three or more rows of cutting elements. The shapes of cutting elements may vary between rows or among rows. For example, a primary or leading row may have conical cutting elements, and a secondary or trailing row may have domed cutting elements. Furthermore, the nominal size (e.g., diameter, characteristic width, extension from the outer surface  214 ) of the cutting elements may vary between rows, or among cutting elements within a row. For example, the cutting elements of a leading row may have a smaller diameter than the cutting elements of a trailing row, and the cutting elements of a tertiary row may be approximately the same size or smaller than the cutting elements of the leading row. Furthermore, the extension of the cutting elements from the outer surface  214  may vary between the rows. The extension of the cutting elements  216  in the leading row may be greater than the extension of secondary cutting elements  217  in one or more trailing rows. Due to the journal angle of the rolling cutting structure  212  of some embodiments, the secondary cutting elements  217  of one or more secondary rows may extend further relative to a face of the bit than the primary cutting elements  216  of the leading row despite shorter extensions of the secondary cutting elements  217  from the outer surface  214  than the primary cutting elements  216 . That is, in some embodiments the cutting profile of the secondary cutting elements  217  may extend further from the leading face of the bit than the cutting profile of the primary cutting elements  216 . The cutting elements of the primary row and any tertiary rows may be configured to engage the formation and reduce wear on the trailing edge of the blade with the rolling cutting structure  212 . 
     The rolling cutting structure  212  may include a journal bore  218 . The journal bore  218  may extend the width  219  of the rolling cutting structure  212 . In some embodiments, a journal and journal axle may be configured to be inserted into the journal bore  218 , and the rolling cutting structure  212  may rotate about the journal axle. 
       FIG. 2-2  is a cross-sectional view parallel to a longitudinal or rotational axis of the rolling cutting structure  212  shown in  FIG. 2-1 , according to at least one embodiment of the present disclosure. The rolling cutting structure  212  may be cylindrical, or approximately cylindrical. The rolling cutting structure  212  has a wheel width  219 . The wheel width  219  may be less than a wheel diameter  220 . For example, the wheel width  219  may be less than 50% of the wheel diameter  220 . In other examples, the wheel width  219  may be less than 40% of the wheel diameter  220 . In still other examples, the wheel width  219  may be less than 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20% 17.5%, 15%, 12.5%, 10%, 8%, 6%, or 5% of the wheel diameter  220 . Thus, because the wheel width  219  is less than, and even much less than, than the wheel diameter  220 , the rolling cutting structure  212  may be wheel-shaped. In other words, a wheel-shaped rolling cutting structure  212  has a wheel width  219  that is less than or significantly less than the wheel diameter  220 . In at least one embodiment, it may be critical that the wheel width  219  is less than 50% of the wheel diameter  220 . In other embodiments, it may be critical that the wheel width  219  is less than 35% of the wheel diameter  220 . These percentages may strike a balance between being supported in a blade (not shown) of a bit and strength of the rolling cutting structure  212 . 
     In some embodiments, a wheel-shaped rolling cutting structure  212  is non-conical (e.g., partially conical, frustoconical, truncated conical, domed, spherical, hemispherical, partially spherical, ellipsoidal, egg-shaped, paraboloidal, and so forth). In other embodiments, the wheel-shaped rolling cutting structure  212  is, e.g., partially conical, frustoconical, truncated conical, or the like. 
     A wheel-shaped rolling cutting structure  212  may include a bevel, such as beveled portion  222 . The bevel  222  may be a different size and/or geometry on each side of the wheel-shaped rolling cutting structure, may be identical on each side of the wheel-shaped rolling cutting structure as shown in  FIG. 2-2 , or may be located only on one side of the wheel-shaped rolling cutting structure. When a bevel  222  is located on one side only or is different on both sides of the wheel-shaped rolling cutting structure, it may appear to be partially conical, and this geometry is considered to be within the scope of the present disclosure. In some embodiments, the wheel diameter  220  may be the same or approximately the same (i.e., within 5%) at a first side  223 - 1  as a second side  223 - 2  of the rolling cutting structure. In some embodiments, the rolling cutting structure  212  may be symmetrical about a plane transverse or perpendicular to the wheel width  219 . 
     In some embodiments, the wheel width  219  may be in a range having an upper value, a lower value, or upper and lower values including any of 0.3 in. (7.62 mm), 0.4 in. (10.16 mm), 0.5 in. (12.70 mm), 0.6 in. (15.24 mm), 0.7 in. (17.78 mm), 0.8 in. (20.32 mm), 0.9 in. (22.86 mm), 1.0 in. (25.40 mm), 1.25 in. (31.75 mm), 1.5 in. (38.1 mm), 1.75 in. (44.45 mm), 2.0 in. (50.8 mm), 2.25 in. (57.15 mm), 2.5 in. (63.50 mm), 2.75 in. (69.85 mm), 3.0 in. (76.2 mm), 3.5 in. (88.90 mm), 4.0 in. (101.6 mm), or any value therebetween. For example, the wheel width  219  may be greater than 0.3 in. (7.62 mm). In another example, the wheel width  219  may be less than 4.0 in. (101.6 mm). In yet other examples, the wheel width  219  may be any value in a range between 0.3 in. (7.62 mm) and 4.0 in. (101.6 mm). 
     In some embodiments, the wheel diameter  220  may be in a range having an upper value, a lower value, or upper and lower values including any of 2.0 in. (5.08 cm), 2.5 in. (6.35 cm), 3.0 in. (7.62 cm), 3.5 in. (8.89 cm), 4.0 in. (10.16 cm), 4.5 in. (11.43 cm), 5.0 in. (12.70 cm), 5.5 in. (13.97 cm), 6.0 in. (15.24 cm), 7.0 in. (17.78 cm), 8.0 in. (20.32 cm), 9.0 in. (22.86 cm), 10.0 in. (25.40 cm), 12 in. (30.48 cm), 14 in. (35.56 cm), 16 in. (40.64 cm), 18 in. (45.72 cm), 20 in. (50.80 cm), 21 in. (53.34 cm), 22 in. (55.88 cm), 24 in. (60.96 cm) 25 in. (63.50 cm), or any value therebetween. For example, the wheel diameter  220  may be greater than 1.0 in. (2.54 cm). In another example, the wheel diameter  220  may be less than 10.0 in. (25.40 cm). In yet other examples, the wheel diameter  220  may be any value in a range between 1.0 in. (2.54 cm) and 10.0 in. (25.40 cm). 
     In some embodiments, the wheel diameter  220  may be a diameter percentage of a bit diameter. In some embodiments, the diameter percentage may be in a range having an upper value, a lower value, or upper and lower values including any of 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or any value therebetween. For example, the diameter percentage may be greater than 10%. In another example, the diameter percentage may be less than 75%. In yet other examples, the diameter percentage may be any value in a range between 10% and 75%. In some embodiments, it may be critical that the diameter percentage is at least 50% to provide for a greater percentage of cutting of the formation by the rolling cutting structure  212 . 
     The outer surface  214  may be located on a radially outer surface of the rolling cutting structure  212 . In some embodiments, the outer surface  214  may include an upper portion  221 . In at least one embodiment, the upper portion  221  may be flat. In some embodiments, the upper portion  221  may be curved (e.g., elliptical, semicircular) or frustoconical. In the embodiment shown, longitudinally across the upper portion  221 , the wheel diameter  220  may remain constant, may not change, or may change only slightly. The cutting elements  216  may be attached to the outer surface  214  at the upper portion  221 . In some embodiments, the rolling cutting structure  212  may include a beveled portion  222  along the outer surface  214 . For example, across the beveled portion  222 , the wheel diameter  220  may decrease toward a side edge  223  of the rolling cutting structure  212 . The beveled portion  222  may help to prevent the rolling cutting structure  212  from contacting the wellbore bottom as the rolling cutting structure engages the formation. Furthermore the beveled portion  222  may help to reduce stress, and therefore cracking, spalling, and breaking, of the rolling cutting structure  212  at the intersection between the outer surface  214  and the side edge  223 . In some embodiments, the outer surface  214  may be beveled along both edges of the rolling cutting structure  212 . In other embodiments, the outer surface  214  may be beveled along a single edge of the rolling cutting structure. One or more cutting elements  216  or rows of cutting elements may be disposed on the beveled portions of the outer surface  214 . For example, leading and/or trailing rows of cutting elements may be disposed on the beveled portions of the outer surface  214 . The one or more cutting elements  216  may not extend axially beyond a leading or trailing face of the rolling cutting structure  212 . 
     In some embodiments, the rolling cutting structure  212  may include an axial race  225 . The axial race  225  may be configured to accept an axial bearing or an axial seal. The rolling cutting structure  212  may include a thrust washer cavity  227 . A thrust washer (not shown) may be inserted between the thrust washer cavity  227  and a blade (not shown) to provide bearing support between the rolling cutting structure  212  and the blade. In at least one embodiment, a thrust washer cavity  227  may be located on either side of the rolling cutting structure  212 . 
       FIG. 3-1  is a representation of a bit  310 , according to at least one embodiment of the present disclosure. The bit  310  may include one or more blades  324 . The bit  310  may be formed of a matrix material, an alloy material (e.g., steel), or any combination thereof. In some embodiments, one or more portions of the bit  310  are formed by an additive manufacturing process. The blade  324  may include a fixed cutting structure and a rolling cutting structure  312 . The rolling cutting structure  312  may include at least some of the same features and characteristics as the rolling cutting structure  212  described in relation to  FIG. 2-1  and  FIG. 2-2 . 
     In some embodiments, the fixed cutting structure  330  may include one or more fixed cutting elements  332 . In some embodiments, the fixed cutting elements  332  may be standard PDC cutting elements. In other embodiments, the fixed cutting elements  332  may be any other type of cutting element used in downhole drilling tools. In some embodiments, the fixed cutting elements  332  may be brazed or welded to the blade  324 . In other embodiments, the fixed cutting elements  332  may be attached to the blade  324  with a rotating connection, such that each fixed cutting element  332  independently rotates about its own longitudinal axis. Therefore, the fixed cutting structure  330  means that the location of the fixed cutting elements  332  do not change with respect to the blade  324 . 
     A journal axle (not shown) may be inserted into a journal cavity  331  in the leading surface of the blade  324 . The journal axle may be secured to the blade  324  using fastener inserted through a cavity  333  at the trailing surface of the blade  324 . For example, a threaded fastener may be inserted into a bolt cavity  333 . The journal axle may secure the rolling cutting structure  312  to the blade  324 . The rolling cutting structure  312  may then rotate about the journal axle. The rolling cutting structure  312  may be secured within a slot  348  of the blade  324 . In some embodiments, as shown in  FIG. 3-1 , one or more slots  348  may be open to a central cavity  385  of the bit  310 . The central cavity  385  may be open to the bit axis  334  and one or more junk slots of the bit  310  as shown in  FIG. 3-1 , or separated from one or more junk slots as shown in  FIG. 5-1 . The rolling cutting structures  312  and the fixed cutting structures  330  may be disposed between the central cavity  385  and the gauge of section of the bit  310 . 
       FIG. 3-2  is a representation of the bit  310  of  FIG. 1 , according to at least one embodiment of the present disclosure. The blade  324  has a leading edge  326  and a trailing edge  328 . In some embodiments, the fixed cutting structure  330  may be located at the leading edge  326  of the blade  324 . The rolling cutting structure  312  may be located at or near a trailing edge  328  of the blade  324 . Thus, the fixed cutting structure  330  and the rolling cutting structure  312  may be located on the same blade (e.g., blade  324 ). The rolling cutting structure  312  may be located within the slot  348  of the blade  324 . 
     In the embodiment shown in  FIG. 3-2 , the bit  310  includes three blades  324 . The three blades  324  may be evenly spaced around a circumference of the bit  310 . In other words, the blades  324  may be spaced 120° apart. In other embodiments, the bit  310  may include less than or more than three blades. For example, the bit  310  may include two blades, spaced 180° apart. In other examples, the bit  310  may include four blades, spaced 90° apart. In yet other examples, the bit  310  may include five, six, seven, eight, nine, ten, or more blades spaced evenly around the circumference of the bit  310 . In at least one embodiment, two or more blades may be spaced unevenly around the circumference of the bit  310 . In other words, two or more blades may have different angular spacing with respect to the other blades of the bit  310 , which could, e.g., result in rolling cutting structures that are unevenly spaced around the bit. The blades  324  may include a fixed cutting structure  330  on the leading edge  326  of the blade  324 , and a rolling cutting structure  312  at the trailing edge  328  of the blade  324 . In at least one embodiment, the rolling cutting structure  312  may be at the leading edge  326  of the blade  324 . 
     In some embodiments, each blade  324  may include a rolling cutting structure  312 . In other embodiments, at least one blade  324  may not include a rolling cutting structure  312 . A bit having a plurality of rolling cutting structures  312  that are not located on each blade  324  of the bit may have one, two, three, four, five, six, seven, eight, nine, ten, or more rolling cutting structures  312 . The more rolling cutting structures  312  may be evenly spaced around a circumference of the bit  310 . For example, the bit  310  may include two rolling cutting structures  312 , spaced 180° apart. In other examples, the bit  310  may include three rolling cutting structures  312 , spaced 120° apart. In yet other examples, the bit  310  may include four, five, six, seven, eight, nine, ten, or more rolling cutting structures  312  spaced evenly around the circumference of the bit  310 . In at least one embodiment, two or more rolling cutting structures  312  may be spaced unevenly around the circumference of the bit  310 . In other words, two or more rolling cutting structures  312  may have different angular spacing with respect to the other rolling cutting structures  312  of the bit  310 . For example, the bit  310  may include two rolling cutting structures  312 , spaced within 30° of 180° apart. That is, the bit  310  may include a first rolling cutting structure  312  space between 150° and 210° of a second rolling cutting structure  312 . Asymmetric spacing of the rolling cutting structures  312  about the bit axis  334  may reduce harmonic vibrations while drilling. 
     In some embodiments, the rolling cutting structures  312  perform a majority of the formation removal during drilling, while the fixed cutting structures  330  clean up the cutting profile of the rolling cutting structures  312 . In other embodiments, the fixed cutting structures  330  may perform a majority of the formation removal during drilling, while the rolling cutting structures  312  clean up the cutting profile of the fixed cutting structures  330 . Including both fixed cutting structures  330  and rolling cutting structures  312  on a blade may improve the rate or penetration and/or the amount of feet drilled before refitting or repairing the bit  310 . Furthermore, rolling cutting structures  312  located on the bit  310  may provide the operator with greater control of the bit, which may improve control over azimuth and inclination while drilling straight or a dogleg. 
     Each rolling cutting structure  312  has a journal axle axis  355 , around which the rolling cutting structure  312  rotates. The journal axle axis  355  may be offset from a bit rotational axis  334  with a roller offset  336 . A reference circle  337  may be centered on the bit rotational axis  334  and have a radius equal to the roller offset  336 . In some embodiments, the roller offset  336  may be a percentage of the bit diameter  338 . In some embodiments, the roller offset  336  percentage may be in a range having an upper value, a lower value, or upper and lower values including any of 5%, 10%, 15%, 20%, 22%, 24%, 25%, 26%, 28%, 30%, 35%, 40%, 45%, or any value therebetween. For example, the roller offset  336  percentage may be greater than 5%. In another example, the roller offset  336  percentage may be less than 45%. In yet other examples, the roller offset  336  percentage may be any value in a range between 5% and 45%. In some embodiments, a roller offset  336  percentage of 20% or greater may be critical to the operation of the bit  310 . 
     As the roller offset  336  increases, the rotational rate of the rolling cutting structures  312  may change, and the cutting elements  316  may scrape the formation with a longer scrape as compared with lower roller offsets  336 . This increased contact scraping along the formation may allow each cutting element  316  to remove more material. The conical shape of the cutting elements  316  may be wear and erosion resistant. In this manner, by using a high roller offset  336  and conical cutting elements  316 , the bit  310  may experience an increased rate of penetration and/or a greater bit durability. 
     A reference line  357  perpendicular to the bit rotational axis  334  may extend from the bit rotational axis  334  to the journal axle axis  355 . A reference circle  337  may be centered on the bit rotational axis and have a radius equal to the roller offset  336 . In other words, the reference circle  337  may be circumscribed around each of the journal axle axes  355  at the roller offset  336 . A tangent line  339  may be tangent to the reference circle  337  at the journal axle axis  355 . A journal axle orientation angle  341  may be an angle between the journal axle axis  355  and the tangent line  339 . In some embodiments, the journal axle orientation angle  341  may be in a range having an upper value, a lower value, or upper and lower values including any of 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, or any value therebetween. For example, the journal axle orientation angle  341  may be 45° or less. In another example, the journal axle orientation angle  341  may be 30° or less. In yet other examples, the journal axle orientation angle  341  may be 15° or less. In still other embodiments, the journal axle orientation angle may be greater than 30°. 
     In at least one embodiment, the reference line  357 , which is perpendicular to both the bit rotational axis  334  and the tangent line  339 , may be a cutting element distance  311  from a cutting element tip  313 . The cutting element tip  313  may be the furthest extent of the cutting element  316  from the rolling cutting structure  312 , or the portion of a cutting element  316  that engages the formation first during drilling. The cutting element distance  311  may be the closest distance to the cutting element tip  313  from the reference line  357  in a plane perpendicular to the bit rotational axis  334  when the cutting element top  313  is at the bottom-most point of rotation of the rolling cutting structure  312  about the journal axis  355 . In some embodiments, the cutting element distance  311  may be in a range having an upper value, a lower value, or upper and lower values including any of 0.1 in. (2.54 mm), 0.2 in. (5.08 mm), 0.3 in. (7.62 mm), 0.4 in. (10.16 mm), 0.5 in. (12.70 mm), 0.6 in. (15.24 mm), 0.7 in. (17.78 mm), 0.8 in. (20.32 mm), 0.9 in. (22.86 mm), 1.0 in. (25.40 mm), or any value therebetween. For example, the cutting element distance  311  may be greater than 0.1 in. (2.54 mm). In another example, the cutting element distance  311  may be less than 1.0 in. (25.40 mm). In yet other examples, the cutting element distance  311  may be any value in a range between 0.1 in. (2.54 mm) and 1.0 in. (25.40 mm). 
     The cutting element distance  311  may be offset in a positive or negative direction. The offset direction may help determine the direction that the rolling cutting structure  312  rolls about the journal  346 . In other words, cutting element distance  311  may be offset in the direction of rotation of the bit (e.g., a positive offset) or against the direction of rotation of the bit (e.g., a negative offset). The direction of offset of the cutting element distance  311  may change the direction of rotation of the rolling cutting structure as the bit rotates. A positive offset may cause the rolling cutting structure  312  to rotate from the center of the bit (e.g., from the bit rotational axis or near the bit rotational axis) toward the outside or the gauge of the bit. A negative offset may cause the rolling cutting structure  312  to rotate from the outside or the gauge of the bit toward the center of the bit. In some embodiments, a rotation from the center of the bit toward the outside or gauge of the bit may be desired as material removed by the cutting elements  316  may be pushed away from the bit rotational axis and the central fluid port (e.g., the central fluid port  340  of  FIG. 3-2 ), thereby helping to prevent clogging the central fluid port. In some embodiments, a first rolling cutting structure  312  is arranged on the bit  310  with a positive offset and a second rolling cutting structure  312  is arranged on the bit  310  with a negative offset, thereby configuring the first rolling cutting structure and the second rolling cutting structure to rotate in opposite directions. 
     The bit  310  may include a central fluid port  340 . In some embodiments, the central fluid port  340  may be located at the bit rotational axis  334 . In other embodiments, the central fluid port  340  may be located at the juncture or the center of all of the slots  348  for the rolling cutting structures  312 . In this manner, the central fluid port  340  may flush cuttings from the rolling cutting structures  312 . Furthermore, the central fluid port  340  may clean the rolling cutting structures  312 . In some embodiments, the bit  310  may include more than one central fluid port  340  in the central cavity  385 . For example, the bit  310  may include the same number of central fluid ports  340  as rolling cutting structures  312 . In other examples, the bit  310  may include more central fluid ports  340  than rolling cutting structures  312 . In still other examples, the bit  310  may include fewer central fluid ports  340  than rolling cutting structures  312 . In some embodiments, the central fluid port  340  may include a nozzle that pressurizes and directs the flow of drilling fluid out of the bit  310 . In other embodiments, the central fluid port  340  may not include a nozzle, but may vent directly from a fluid chamber inside the body of the bit. 
     The bit  310  may include a blade nozzle  342 . The blade nozzle  342  may be located in a depression or junk slot between blades  324 . In some embodiments, the blade nozzle  342  may direct drilling fluid across the fixed cutting structure  330 . This may help wash cuttings away from the fixed cutting structure  330  and clean the cutting elements of the fixed cutting structure  330 . In some embodiments, each blade  324  may have a blade nozzle  342 . In some embodiments, each blade  324  may include more than one blade nozzle  342  to better clean the fixed cutting structure. 
     The blade  324  may include a support leg  344  at the trailing edge  328  of the blade  324 . The support leg  344  may support an end of the rolling cutting structure  312 . For example, a journal axle may be inserted into a cavity in the blade  324  at the leading edge  326  or the trailing edge  328 . A first end of the journal axle may be supported by the leading edge  326  of the blade  324 , and a second end of the journal axle may be supported by the support leg  344 . 
       FIG. 3-3  is a cross-sectional view of a blade  324 , according to at least one embodiment of the present disclosure. The blade  324  may include a journal cavity  331  and a rolling slot  348 . The rolling slot  348  may be wide enough to allow a rolling cutting structure  312  to be inserted into the rolling slot  348 . To secure the rolling cutting structure  312  to the blade  324 , the journal  346  may be inserted into the journal cavity  331  and through a journal bore  318  in the rolling cutting structure  312  when the rolling cutting structure  312  is inserted in the rolling slot  348 . 
     In some embodiments, the journal  346  may be secured to the blade  324  with a journal attachment  350 . The journal attachment may include a threaded fastener  351 , such as a screw or a bolt. The threaded fastener  351  may be inserted through a bolt hole  352  and into matching threads in the journal  346 . As the threaded fastener  351  is tightened, the journal  346  may be drawn towards the bolt hole  352 . A washer  353  may spread the load of the tightened threaded fastener  351  across the bolt hole  352 . Thus, the journal  346  may be securely fastened to the blade  324  in the journal cavity  331 . The threaded fastener  351  may be accessed through a bolt cavity  333  in the blade  324 . 
     In some embodiments, the journal cavity  331  may extend across the rolling slot  348  to the other side (i.e., trailing edge  328 ) of the blade  324 . Therefore, the journal  346  may be supported on both a journal first end  354 - 1  and a journal second end  354 - 2 . The blade  324  may include a support leg  344  located at a trailing edge  328  of the blade  324 . The bolt cavity  333  and the bolt hole  352  may be located in the support leg  344 , and the journal cavity  331  may extend into the support leg  344 . Thus, the journal  346  may be inserted into the journal cavity  331 , inserted through the journal bore  318  of the rolling cutting structure  312 , inserted into a portion of the journal cavity  331  on the support leg  344 , and secured to the blade  324  at the journal attachment  350 . In this manner, the journal  346  may be supported at the journal first end  354 - 1  near or at the leading edge  326  and at the journal second end at the support leg  344  near or at the trailing edge  328 . Because the journal  346  supports the rolling cutting structure  312 , the rolling cutting structure  312  is supported by the blade near the leading edge  326  and by the support leg  344  near or at the trailing edge  328 . 
     In at least one embodiment, the blade  324  may not include a support leg  344 . In this manner, the journal cavity  331  may extend through the blade  324 , and the rolling cutting structure  312  may be cantilevered out in the trailing direction behind the blade  324 . For example, the journal cavity  331  may be strengthened using hardened materials or additively manufactured structures internal to the leading edge of the blade  324 . This may account for any additional forces caused by the cantilevered rolling cutting structure  312  on the blade  324 . 
     In some embodiments, the journal cavity  331  may be located on the leading edge  326  of the blade  324 . For example, the journal cavity  331  may be located below the fixed cutting structure  330  on the leading edge  326  of the blade  324 . The bolt cavity  333  may be located on the support leg  344 , or in other words, on the trailing edge  328  of the blade  324 . In other embodiments, the journal cavity  331  may be located on the trailing edge  328  of the blade  324 , and the bolt cavity  333  may be located on the leading edge  326  of the blade  324 . 
     In some embodiments, the journal  346  may be a journal axle. Grease for the journal  346  may be located in a grease reservoir  356 . The grease reservoir  356  may be integrally formed within the journal  346  or may be a separate component disposed within the journal  346 . Grease may be communicated to the journal axle through grease ports  358  in the journal  346 . The journal  346  may have an increased diameter or cross-sectional area in the section of the cavity  331  that supports the journal  346 . This may increase the volume of the grease reservoir  356 , thereby allowing greater lubrication and/or operational lifetime of the journal  346 . In at least one embodiment, the grease reservoir  356  may be offset from the journal axle axis  355  to accommodate placement of one or more of the grease ports  358 . The journal axle may include a sleeve that extends around an exterior of the journal  346 . In some embodiments the sleeve may extend at least partially into the journal cavity  331 . The sleeve may help to secure the journal  346  in place and spread any load experienced by the journal  346 . A compensation hole  364  through the journal  346  and the journal attachment  350  may facilitate distribution of the grease from the reservoir  356  by exposure to the downhole pressure. Additionally, a fastener  365  (e.g., snap ring) may be configured to secure the grease reservoir  356  within the journal  346 . 
     In some embodiments, a plurality of bearings  323  are disposed in bearing races  325  between the rolling cutting structure  312  and the blade  324 . In some embodiments, a friction bearing provides axial support along the journal axis  355  between the rolling cutting structure  312  and the portions of the blade  324  along the slot  348 . As noted above with  FIG. 2-2 , thrust washers  360  may be arranged in thrust washer cavities  327  of the rolling cutting structure  312 . These thrust washers  360  and bearings  323  may be configured to center the rolling cutting structure within the slot  348 . In some embodiments, the thrust washers  360  are radially outside the bearings  323  or friction bearing. One or more journal seals  361  are configured to reduce or eliminate intrusion of drilling fluid into the journal system. In some embodiments, one or more reservoir seals  362  are configured to isolate the grease within the journal. The journal seals  361  and reservoir seals  362  may include, but are not limited to o-rings, oval seals, bullet seals, or other types of seals. 
     The cutting elements  316  of the rolling cutting structure  312  may have an exposure, which is a distance that the cutting elements  316  may cut into the formation. Furthermore, the fixed cutting elements  332  of the fixed cutting structure  330  may have an exposure. In some embodiments, the fixed cutting elements  332  exposure may be the same as the cutting elements  316  exposure. In some embodiments, the fixed cutting elements  332  exposure may be different than the cutting elements  316  exposure. The differing exposures may be seen in a view where the fixed cutting elements  332  and the cutting elements  316  are rotated into the same plane about the bit axis  334  for comparison. 
     For example, the cutting elements  316  of the rolling cutting structure  312  may have a greater exposure than the fixed cutting elements  332 . In other words, the cutting elements  316  may extend further into the formation than the fixed cutting elements  332  at a given location. Therefore, in at least one embodiment, the cutting elements  316  extend past the end of the bit  310  further than the fixed cutting elements  332 . In this manner, the cutting elements  316  may cut more of the formation than the fixed cutting elements. In some embodiments, the fixed cutting elements  332  may clean up the wellbore bottom from material left uncut by the cutting elements  316 . 
     The cutting elements  316  exposure may be positive or negative. As used in this disclosure, a positive exposure is the extent the cutting elements  316  extends past the other cutting elements (e.g., the fixed cutting elements or cutters on the other rolling cutting structures). A negative exposure is the extent below the other cutting elements (e.g., the fixed cutting elements or cutters on the other rolling cutting structures) that the cutting elements  316  may be positioned. In some embodiments, the cutting elements  316  exposure may be in a range having an upper value, a lower value, or upper and lower values including any of −0.300 in. (−7.62 mm), −0.250 in. (−6.35 mm), −0.200 in. (−5.08 mm), −0.150 in. (−3.81 mm), −0.100 in. (−2.54 mm), −0.075 in. (−1.91 mm), −0.050 in. (−1.27 mm), −0.025 in. (−0.64 mm), 0.025 in. (0.64 mm), 0.050 in. (1.27 mm), 0.075 in. (1.91 mm), 0.100 in. (2.54 mm), 0.150 in. (3.81 mm), 0.200 in. (5.08 mm), 0.250 in. (6.35 mm), 0.300 in. (7.62 mm), or any value therebetween. For example, the cutting elements  316  exposure may be greater than −0.300 in. (−7.62 mm). In another example, the cutting elements  316  exposure may be less than 0.300 in. (7.62 mm). In yet other examples, the cutting elements  316  exposure may be any value in a range between −0.300 in. (−7.62 mm) and 0.300 in. (7.62 mm). In some embodiments, the cutting elements  316  exposure could be less than −0.300 in. (−7.62 mm) or greater than 0.300 in. (7.62 mm). In at least one embodiment, it may be critical that the exposure is between −0.050 in. (−1.27 mm) and 0.050 in. (1.27 mm) to provide the maximum rate of penetration and prevent excessive wear of the cutting elements  316 . In some embodiments, different rolling cutting structures  312  may have different exposures. For example, one or more rolling cutting structures  312  may have a negative exposure, one or more rolling cutting structure  312  may have a positive exposure, and one or more rolling cutting structure  312  may have an exposure of 0 in. (0 mm), or any combination thereof. 
     In some embodiments, the cutting elements  316  exposure may be adjustable. For example, a larger diameter rolling cutting structure  312  may increase the exposure of the cutting elements  316 . In other examples, larger cutting elements  316  may increase the exposure of the cutting elements  316 . In some examples, a combination of changing the diameter of the rolling cutting structure  312  and the size of the cutting elements  316  may change the exposure of the cutting elements  316 . 
     The journal  346  has a journal axle axis  355 . The rolling cutting structure  312  may rotate about the journal  346  on a journal axle about the journal axle axis  355 . In some embodiments, the journal axle axis  355  may be parallel to a reference line  357 , the reference line  357  being perpendicular to a bit rotational axis (such as the bit rotational axis  334  of  FIG. 3-2 ). A journal angle  359  may be the angle between the journal axle axis  355  and the reference line  357 . In some embodiments, the magnitude of the journal angle  359  may be in a range having an upper value, a lower value, or upper and lower values including any of 0°, 5°, 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, 30°, 35°, 40°, 45° or any value therebetween. For example, the journal angle  359  may be greater than 0°. In another example, the journal angle  359  may be less than 45°. In yet other examples, the journal angle  359  may be any value in a range between 0° and 45°. In some embodiments, the journal angle  359  may be greater than 45°. 
     In some embodiments, the journal angle  359  may affect the angle at which the cutting elements  316  engage the formation. Therefore, the journal angle  359  may be optimized for the angle at which the cutting elements  316  engage the formation. A journal angle of 17° or within 10° of 17° may be critical to optimize the drilling of the bit. The journal angle  359  may be positive or negative. In some embodiments, the cutting elements  316  may be attached to the rolling cutting structure to affect the angle at which the cutting elements  316  engage the formation. For example a first row of cutting elements  316  may be arranged with cutting element axes perpendicular to the axis of the rolling cutting structure  312 , and a second row of cutting elements  317  may be arranged with cutting element axes at a different angle to the axis of the rolling cutting structure. Thus, in some embodiments, the cutting elements  316  of the rolling cutting structure  312  may be attached to provide a desired angle of engagement with the formation regardless of the journal angle  359 . 
       FIG. 3-4  is a cutting-element profile of the bit  310  of  FIG. 3-1 , according to at least one embodiment of the present disclosure. A cutting element profile  329  represents the outermost extent of the cutting elements (e.g., cutting elements  316  of  FIG. 3-2 ) on a rolling cutting structure (e.g., rolling cutting structure  312  of  FIG. 3-2 ), as rotated about a bit rotational axis  334 . A secondary cutting element profile  335  represents the outermost extent of the secondary cutting elements (e.g., secondary cutting elements  217  of  FIG. 2-1 ), as rotated about the bit rotational axis  334 . A fixed cutting element profile  345  represents the outermost extent of the fixed cutting elements (e.g., fixed cutting elements  332  of  FIG. 3-3 ), as rotated about the bit rotational axis  334 . 
     As may be seen, the cutting element profile  329  extends the furthest downward, or has the highest exposure approximately halfway between the bit rotational axis  334  and the borehole wall. The cutting elements that have the highest exposure may experience the greatest forces and remove a majority of the formation while drilling. Thus, the cutting element profile  329  indicates that the cutting elements perform most of the cutting in the bit. In other embodiments the fixed cutting element profile  345  may extend further downward than the cutting element profile  329 . Thus, the fixed cutting element profile would cut the majority of the formation in the region halfway between the borehole wall and the bit axis  334 . From a center portion of the profiles inside of where the fixed cutting element profile  345  extends the furthest downward, the cutting element profile  329  may extend further downward than the secondary cutting element profile  335  and would therefore cut the majority of the formation in this zone. 
     The exposure of the cutting elements  316  of the one or more rolling cutting structures  312  may differ from the exposure of the fixed cutting elements  332  on the blades  324 . The fixed cutting elements  332  may be configured to engage the formation in one or more of a gauge section  370 , a shoulder section  372 , a nose section  374 , or any combination thereof. In some embodiments, the fixed cutting elements  332  on the blades  324  may be configured to not engage with the formation in a cone region  376  of the bit nearest the bit axis  334 . As illustrated in  FIG. 3-4 , the exposure  345  of the fixed cutting elements  322  may not include the cone region  376  nearest the bit axis  334 .  FIGS. 3-1 and 3-2  illustrate embodiments of the bit  310  without fixed cutting elements in the cone region  376 . That is, the cutting elements  316  of the rolling cutting structures  312  may be the only cutting structures within the cone region  376 . One or more rows of the cutting elements  316  may have exposure to the formation in at least the cone region  376 . The exposures  329  and  335  of the cutting elements  316  on the rolling cutting structures  312  may overlap with the exposure  345  of the fixed cutting elements  332  in one or more of the nose region  374 , the shoulder region  372 , and the gauge region  370 . In some embodiments, the exposures  329  and  335  of the cutting elements  316  on the rolling cutting structures  312  are less than or equal to the exposure  345  of the fixed cutting elements  332  wherever the respective exposures overlap. 
       FIG. 3-5  is a cross sectional view of the blade  324  of  FIGS. 3-2 and 3-3  taken transverse to the view shown in  FIG. 3-3 , according to at least one embodiment of the present disclosure. The journal cavity  331  has a journal cavity height  343  extending from a journal cavity top  375  to a journal cavity bottom  347 . The journal cavity  331  further has a journal cavity width  349 . 
     In some embodiments, the journal cavity  331  may have a generally circular cross section. In other embodiments, the journal cavity  331  may have cross section with a domed top section and a domed bottom section, with a straight middle section. In still other embodiments, the journal cavity may have an ellipsoidal cross section. In yet other embodiments, the journal cavity  331  may be approximately rectangular shaped, or rectangular with rounded corners. In still other embodiments, the journal cavity  331  may have a cross-section that is polygonal, including polygons of  5  or more sides. 
     In some examples, the journal cavity width  349  may be the same as the journal cavity height  343 . For example, the journal cavity  331  may be approximately square or circular. In other examples, the journal cavity  331  may be rectangular or ellipsoidal, meaning that journal cavity width  349  may be less than the journal cavity height  343 . In some embodiments, a rectangular journal cavity  331  may have a more favorable force distribution for the forces experienced by the blade  324 . 
       FIG. 4  is an embodiment of a sleeve  460 , according to at least one embodiment of the present disclosure. The sleeve  460  may include a back plate  461 . In some embodiments, the back plate  461  may be configured to abut against an inner surface of a rolling cavity (e.g., rolling slot  348  of  FIG. 3-2 ). In some embodiments, two sleeves  460  may be placed on either side of a rolling slot (e.g., rolling slot  348  of  FIG. 3-3 ). Thus, a plurality of sleeves may be configured to support a rolling cutting structure (e.g., rolling cutting structure  212  of  FIG. 2-1 ). 
     A sleeve extension  462  may extend from the back plate  461  with the sleeve extension journal bore  463  extending therethrough. The sleeve extension has a top surface  464  and a bottom surface  465 . A top thickness  466  may be the thickness of the sleeve extension  462  between the sleeve extension journal bore  463  and the top surface  464 . A bottom thickness  467  may be the thickness of the sleeve extension  462  between the journal bore and the bottom surface  465 . 
     In some embodiments, the sleeve  460  may have an outer profile that matches the profile of the journal cavity (e.g., journal cavity  331  of  FIG. 3-5 ), and an inner profile that matches the outer circumference of the journal (e.g., journal  346  of  FIG. 3-3 ). Therefore, the profile of the journal cavity may be different than the profile of the journal. In this manner, the sleeve  460  may distribute the forces experienced by the rolling cutting structure to the journal cavity. Thus, the journal cavity may be designed to distribute forces from the rolling cutting structure (e.g., the rolling cutting structure  312  of  FIG. 3-1 ) to the blade, and the sleeve  460  may be designed to nest the journal within the journal cavity, and to transfer forces experienced by the journal from the rolling cutting structure to the journal cavity. 
     In some embodiments, the top thickness  466  may be the same as the bottom thickness  467 . In other embodiments, the top thickness  466  may be different from the bottom thickness  467 . In this manner, the relative position of the journal within the journal cavity may be adjusted by providing sleeves  460  with differing top thicknesses  466  and bottom thicknesses  467 . In other words, the height of the journal within the journal cavity may be adjusted by changing the sleeve  460  to a sleeve  460  having a different top thickness  466  and a different bottom thickness  467 . Therefore, the rolling cutting structure may have an adjustable height. This may allow the height of the rolling cutting structure to be changed with respect to the rest of the bit. Specifically, the height or position of the rolling cutting structure with respect to the fixed cutting structure may be changed. In other words, the exposure of the cutting elements (e.g., cutting elements  316  of  FIG. 3-3 ) may be changed or adjusted relative to the fixed cutting elements (e.g., fixed cutting elements  332  of  FIG. 3-3 ) by changing the sleeve  460 . In other embodiments, other adjustment mechanisms may be used. For example, a ratcheting mechanism, a flow control valve, a stepper motor, or other adjustment mechanism may be used to adjust the height of the journal. Examples of adjustment mechanisms may be seen in United States Patent Publication Number 2018/0087323, filed Mar. 27, 2016, which is hereby incorporated by reference in its entirety for all purposes. 
     Similarly, a side thickness  469  of the sleeve  460  may be adjusted. In this manner, the offset (e.g., roller offset  336  of  FIG. 3-2 ) may be adjusted. In other words, the offset of the rolling cutting structure may be adjustable. For example, a sleeve  460  having different side thicknesses  469  may be inserted into the journal cavity, thereby changing the offset of the rolling cutting structure. In some embodiments, the side thickness  469 , the top thickness  466 , and the bottom thickness  467  may be changed at the same time. In other words, both the journal offset and the journal height may be adjusted at the same time. 
     In some embodiments, the sleeve  460  may be reversible. In other words, the sleeve  460  may be able to be installed such that the top surface  464  engages a bottom surface of the journal cavity and a bottom surface  465  may engage a top surface of the journal cavity, and vice versa. In this manner, the height and exposure of the journal and the rolling cutting structure may be quickly adjusted, e.g., in the field at the drill rig. 
       FIG. 5-1  is a perspective view of a representation of a bit  510 , according to at least one embodiment of the present disclosure. The bit  510  may include at least some of the same features and characteristics as the rolling cutting structures and bits described in relation to  FIG. 2-1  through  FIG. 4 . The bit  510  may include a plurality of blades  524 . In the embodiment shown, the bit  510  includes a plurality of fixed cutting structures  530  and rolling cutting structures  512 . The rolling cutting structures  512  may be attached to a blade  524  using a journal  546  installed in a journal cavity  531 . The fixed cutting structures of a blade  524  with a rolling cutting structure  512  may be split into an upper blade section  580  and a lower blade section  581  to facilitate the journal cavity  531 . The upper blade section  580  and the lower blade section  581  may each have a plurality of fixed cutting elements arranged thereon. 
       FIG. 5-2  is a bottom view of the bit  510  of  FIG. 5-1 . As may be seen, in some embodiments, the bit  510  may include four blades (collectively  524 ). A first blade  524 - 1  may include a first fixed cutting structure  530 - 1  at a leading edge  526  of the first blade  524 - 1 . A rolling cutting structure (collectively  512 ) may be attached to the first blade  524 - 1  at a trailing edge  528 . The rolling cutting structure  512  may be attached to the first blade  524 - 1  and supported by a support leg  544 . A second blade  524 - 2  may include a single cutting structure, i.e., the second fixed cutting structure  530 - 2 . In some embodiments, slots  548  for the rolling cutting structures  512  may be open to a central cavity  585 , as shown in  FIG. 5-2 . 
     In some embodiments, the bit  510  include a first set of blades and a second set of blades. The first set of blades may include two or more first blades  524 - 1 . The second set of blades may include two or more second blades  524 - 2 . 
     The bit  510  may have twice as many fixed cutting structures (collectively  530 ) as rolling cutting structures  512 . In some embodiments, a secondary blade, or fixed cutting structure  530 , may be located on either side or both sides of each rolling cutting structure  512 . In other words, each fixed cutting structure  530  may have a rolling cutting structure  512  located on a first side of the fixed cutting structure  530 , and a fixed cutting structure  530  on a second side of the fixed cutting structure. 
     In some embodiments, the first blade  524 - 1  may only include a rolling cutting structure  512 , without a first fixed cutting structure  530 - 1 . In such an embodiment, the bit  510  has six blades  524 , each blade  524  including a single cutting structure. 
     In some embodiments, the bit  510  may include a first rolling cutting structure  512 - 1  and a second rolling cutting structure  512 - 2 . Both rolling cutting structures  512 - 1 ,  512 - 2  may have a journal angle (e.g., journal angle  359  of  FIG. 3-3 ). Because the first rolling cutting structure  512 - 1  is located on the opposite side of the bit  510  from the second rolling cutting structure  512 - 2 , the first rolling cutting structure  512 - 1  appears to be angled in a different direction from the second rolling cutting structure  512 - 2 . However, the rolling cutting structures  512 - 1 ,  512 - 2  are angled in the same rotational direction. However, in some embodiments, because of the journal angle, the formation may not be completely worn away near the bit rotational axis  534 . In some embodiments, a separation distance between cutting elements across the bit rotational axis  534  may be between 0 to 1.0 inches, 0.25 to 0.75 inches, 0.3 to 0.6 inches, or approximately 0.5 inches. Therefore, the rolling cutting structures  512 - 1 ,  512 - 2  may include a second row of secondary cutting elements (e.g., the secondary cutting elements  217  of  FIG. 2-1 ). These secondary cutting elements may assist in removing the formation at the bit rotational axis  534 . 
       FIG. 5-3  is a side view of the bit  510  of  FIG. 5-1 , according to at least one embodiment of the present disclosure. As discussed above, the rolling cutting structure  512  may be secured to the bit  510  using a journal  546  installed in a journal cavity  531 . In some embodiments, the journal cavity may be installed in a slot  548  of a blade  524  below a fixed cutting structure  530 . However, this may reduce the amount of available room for fixed cutting elements  532  on the fixed cutting structure  530 . Therefore, in some embodiments, one or more gauge cutting elements  568  may be located near or above the rolling cutting structure  512 . Thus, in at least one embodiment, the fixed cutting structure  530  may have a set of fixed cutting elements  532  located separately from the gauge cutting elements  568 . That is, the fixed cutting structure  530  of the blade  524  may have the upper blade section  580  and the lower blade section  581   
       FIG. 6  is a bottom view of a representation of a bit  610 , according to at least one embodiment of the present disclosure. The bit  610  may include at least some of the same features and characteristics as the rolling cutting structures and bits described in relation to  FIG. 2-1  through  FIG. 5-3 . The bit  610  may include a plurality of blades  624 . Each blade  624  may include a fixed cutting structure  630  on a leading edge  626  and a rolling cutting structure  612  on a trailing edge  628  of the blade  624 . 
     In this manner, the bit  610  may include an equal number of fixed cutting structure  630  to rolling cutting structures  612 . In other words, a fixed cutting structure  630  may be located on either side of each rolling cutting structure  612 , and a rolling cutting structure  612  may be located on either side of each fixed cutting structure  630 . 
     A central gap  670  (e.g., central cavity) may be located at the convergence of the plurality of rolling cutting structures  612 . The central gap  670  may include a plurality of central fluid jets  672 . The plurality of central fluid jets  672  may be directed at the rolling cutting structures  612  such that the central fluid jets  672  clean the rolling cutting structures  612  and flush cuttings from the central gap  670 . In some embodiments, the bit  610  may include a central fluid jet  672  for each rolling cutting structure  612 . In other embodiments, there may be more central fluid jets  672  than rolling cutting structures. In still other embodiments, there may be fewer central fluid jets  672  than rolling cutting structures. 
     In some embodiments, the cutting elements  616  may not reach completely to the center of the bit  610 . Therefore, there may be a separation distance  676  between two opposing rolling cutting structures  612 . This separation distance  676  may be a result of the journal offset, the journal angle, the placement of the rolling cutting structures  612  in general, or any combination of the foregoing. In some embodiments, one or more central cutting elements  674  may be placed on the bit  610  at the center of the central gap  670  to break up any formation that is not broken by the rolling cutting structure  612 . The separation distance  676  may be between approximately 0.1 to 1.0 inches, 0.25 to 0.75 inches, 0.3 to 0.6 inches, or approximately 0.5 inches. In some embodiments, the separation distance  676  between opposing rolling cutting structures  612  may be negative. That is, the cutting elements  616  of the opposing rolling cutting structures  612  may overlap a plane through the bit axis  634  such that the cutting profile extends across the bit axis  634 . These rolling cutting structures  612  are arranged on different planes, which is configured to eliminate interference of the cutting elements  616 . 
     In other embodiments, two opposing rolling cutting structures  612  may be placed or adjusted to reduce the separation distance  676 . For example, two opposing rolling cutting structures  612  may be placed with a smaller roller offset than the other two rolling cutting structures  612 . In other examples, two opposing rolling cutting structures  612  may have larger wheel diameters (e.g., wheel diameter  220  of  FIG. 202 ) than the other two rolling cutting structures  612 . In still other examples, some combination of rolling cutting structure placement, wheel diameter, and a central cutting element  674  may help to break up the formation not cut in the central gap  670 . 
     A blade nozzle  678  may be located between each blade  624 . The blade nozzle  678  may be configured to clean the fixed cutting structure  630 . In some embodiments, the blade nozzle  678  may be oriented at a blade nozzle angle, relative to the bit rotational axis  634 . In some embodiments, the blade nozzle angle may be parallel to the bit rotational axis  634 . In other embodiments, the blade nozzle angle may be in a range having an upper value, a lower value, or upper and lower values including any of 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, or any value therebetween. For example, the blade nozzle angle may be greater than 5°. In another example, the blade nozzle angle may be less than 85°. In yet other examples, the blade nozzle angle may be any value in a range between 5° and 85°. In some embodiments, a blade nozzle angle of approximately 45° may be critical to effectively clean the fixed cutting structures  630 . 
       FIG. 7-1  is a perspective view of a bit  710 , according to at least one embodiment of the present disclosure. The bit  710  may include at least some of the same features and characteristics as the rolling cutting structures and bits described in relation to  FIG. 2-1  through  FIG. 6 . For example, the bit  710  may include two first blades  724 - 1  arranged opposite one another, and two second blades  724 - 2  arranged transverse to the first blades  724 - 1  and opposite each other. Each first blade  724 - 1  may include a fixed cutting structure  730 . Each second blade  724 - 2  may include a first rolling cutting structure  712 - 1  and a second rolling cutting structure  712 - 2 . The first rolling cutting structure  712 - 1  may be separated from the second rolling cutting structure  712 - 2  by a central support leg  772 . 
       FIG. 7-2  is a bottom view of the bit  710  of  FIG. 7-1 . Each second blade  724 - 2  may include a second blade leading edge  726 - 2  and a second blade trailing edge  728 - 2 . The first rolling cutting structure  712 - 1  may be located on the second blade leading edge  726 - 2  and the second rolling cutting structure  712 - 2  may be located on the second blade trailing edge  728 - 2 . 
     The bit  710  may include one or more central fluid ports  740 . The central fluid ports  740  may be located near the bit rotational axis  734  between second blades  724 - 2 , and configured to flush cuttings away from the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2 . A blade nozzle  742  may be located on one or more of the first blades  724 - 1  and configured to clean and wash cutting away from the fixed cutting structures  730 . An outer nozzle  774  may be located on an outer perimeter of the bit  710 . The outer nozzle  774  may be configured to further clean the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2 . 
       FIG. 7-3  is a cross-sectional view of a second blade  724 - 2  of the bit  710  shown in  FIGS. 7-1 and 7-2 . The second blade  724 - 2  may support the first rolling cutting structure  712 - 1  at the second blade leading edge  726 - 2  and the second rolling cutting structure  712 - 2  at the second blade trailing edge  728 - 2 . A first journal  746 - 1  may secure the first rolling cutting structure  712 - 1  to a first support leg  744 - 1  and the central support leg  772 . A second journal  746 - 2  may secure the second rolling cutting structure  712 - 2  to a second support leg  744 - 2  and the central support leg  772 . 
     In some embodiments, one or more of the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2  may be angled relative to the bit rotational axis  734 . For example, the first journal  746 - 1  may have a first journal axle axis  755 - 1 , about which the first rolling cutting structure  712 - 1  may rotate. The second journal  746 - 2  may have a second journal axle axis  755 - 2 , about which the second rolling cutting structure  712 - 2  may rotate. In some embodiments, the first journal axle axis  755 - 1  and the second journal axle axis  755 - 2  may be perpendicular to the bit rotational axis  734 . 
     In other embodiments, the first journal axle axis  755 - 1  may be angled with a first journal angle  759 - 1  relative to a reference line  757 , the reference line  757  being perpendicular to the bit rotational axis  734 . Similarly, the second journal axle axis  755 - 2  may have a second journal angle  759 - 2  relative to the reference line  757 . In some embodiments, the first journal angle  759 - 1  and the second journal angle  759 - 2  may have different signs. For example, the first journal angle  759 - 1  may be negative, and the second journal angle  759 - 2  may be positive. In other examples, the first journal angle  759 - 1  may be positive and the second journal angle  759 - 2  may be negative. In other embodiments, the first journal angle  759 - 1  and the second journal angle  759 - 2  may have the same sign. For example, the first journal angle  759 - 1  and the second journal angle  759 - 2  may both be positive. In other examples, the first journal angle  759 - 1  and the second journal angle  759 - 2  may both be negative. 
     As the bit  710  rotates, the rolling cutting structures  712 - 1 ,  712 - 2  may rotate about the journal axle axis  755 - 1 ,  755 - 2 . In some embodiments, the rolling cutting structures  712 - 1 ,  712 - 2  may rotate from the bit rotational axis  734  to an outer perimeter of the bit  710 . In other embodiments, the rolling cutting structures  712 - 1 ,  712 - 2  may rotate from the outer perimeter of the bit  710  to the bit rotational axis  734 . In some embodiments, both the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2  may rotate in the same direction (i.e., from the bit rotational axis  734  to the outer perimeter of the bit  710  or from the outer perimeter of the bit  710  to the bit rotational axis  734 ). In other embodiments, the first rolling cutting structure  712 - 1  may rotate in a different direction from the second rolling cutting structure  712 - 2 . For example, the first rolling cutting structure  712 - 1  may rotate from the bit rotational axis  734  to the outer perimeter of the bit  710  and the second rolling cutting structure  712 - 2  may rotate from the outer perimeter of the bit  710  to the bit rotational axis  734 . In another example, the first rolling cutting structure  712 - 1  may rotate from the outer perimeter of the bit  710  to the bit rotational axis  734  and the second rolling cutting structure  712 - 2  may rotate from the bit rotational axis  734  to the outer perimeter of the bit  710 . 
     Rolling cutting structures  712 - 1 ,  712 - 2  that rotate in opposite directions, or counter-rotating rolling cutting structures  712 - 1 ,  712 - 2 , may cut the formation in different ways, which may improve the rate of penetration of the bit  710 , the life of the bit  710 , and/or decrease maintenance of the bit  710 . For example, first cutting elements  716 - 1  on the first rolling cutting structure  712 - 1  may cut a first path in a first direction in the formation. Second cutting elements  716 - 2  on the second rolling cutting structure  712 - 2  may cut a second path in a second direction in the formation. Because the second direction is different from the first direction, then the second cutting elements  716 - 2  may not engage the formation in the same furrows or divots left by the first cutting elements  716 - 1 . This may reduce wear on the rolling cutting structures  712 - 1 ,  712 - 2 . Further, the fracture patterns of the formation caused by the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2  may be different. This may cause the formation to more easily break up and/or to break up into smaller pieces. 
     The second blade  724 - 2  may include a journal cavity  731 . The journal cavity  731  may extend through the first support leg  744 - 1  and through at least a part of the second support leg  744 - 2 . To install the rolling cutting structures  712 - 1 ,  712 - 2 , the second journal  746 - 2  may be inserted through the second rolling cutting structure  712 - 2  and into the journal cavity  731  located in the second support leg  744 - 2 . The second journal  746 - 2  may be secured to the central support leg  772 . Then the first journal  746 - 1  may be inserted into the journal cavity  731  located in the first support leg  744 - 1 , through the first rolling cutting structure  712 - 1 , and secured to the central support leg  772 . Therefore, the central support leg  772  may support one or both of the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2 . 
     In some embodiments, the first journal  746 - 1  and the second journal  746 - 2  may be independently secured to the central support leg  772 . In other embodiments, a connector bolt  776  may pass through a portion of the central support leg  772 . The connector bolt  776  may connect to both the first journal  746 - 1  and the second journal  746 - 2 . As the connector bolt  776  is placed in tension, the first journal  746 - 1  and the second journal  746 - 2  may be drawn toward and secured against the central support leg. In some embodiments, the connector bolt  776  may be a screw with the head in a cavity of one journal and the threaded portion in a cavity including matching threads of the other journal. In other embodiments, the connector bolt  776  may be any type of mechanical connector. 
     In some embodiments, a bolt cavity  733  may be located in the second support leg  744 - 2 . A threaded fastener  751  inserted into the bolt cavity  733  may secure the second journal  746 - 2  to the second support leg  744 - 2 . Therefore, the first journal may be secured inside the journal cavity  731  by being connected to the central support leg  772  and the second journal  746 - 2  through the connector bolt  776 . 
     In some embodiments, the central support leg  772  may be integrally formed with a bit body  773 . In other words, the central support leg  772  may be formed as a single piece with the bit body  773 . In other embodiments, the central support leg  772  may be formed separately and connected to the bit body  773 . For example, the central support leg  772  may be connected to the bit body  773  by braze, weld, screw, bolt, interference fit (e.g., dovetail joint), friction fit, or other means of connection. 
     In some embodiments, the central support leg  772  may include one or more wear pads or hard facing located at a bottom of the central support leg  772 . In this manner, the central support leg  772  may be protected from any portions of the formation that may not be cut by the rolling cutting structures  712 - 1 ,  712 - 2 . 
     The first rolling cutting structure  712 - 1712 - 2  may have different exposures. In some embodiments, parameters of the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2  may be changed to ensure that the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2  have the same or approximately the same exposure. 
     In some embodiments, the first journal  746 - 1  may be coaxial with the second journal  746 - 2 . In other words, the first journal axle axis  755 - 1  may be the same as, or coincide with, the second journal axle axis  755 - 2 . In other embodiments, the first journal axle axis  755 - 1  may be different from, or offset from, the second journal axle axis  755 - 2 , with a vertical axis offset  780 . In some embodiments, the vertical axis offset  780  may be in a range having an upper value, a lower value, or upper and lower values including any of 0.1 in. (2.54 mm), 0.2 in. (5.08 mm), 0.3 in. (7.62 mm), 0.4 in. (10.16 mm), 0.5 in. (12.70 mm), 0.6 in. (15.24 mm), 0.7 in. (17.78 mm), 0.8 in. (20.32 mm), 0.9 in. (22.86 mm), 1.0 in. (25.40 mm), 1.5 in. (38.1 mm), 2 in. (50.8 cm), or any value therebetween. For example, the vertical axis offset  780  may be greater than 0.1 in. (2.54 mm). In another example, the vertical axis offset  780  may be less than 2.0 in. (50.8 mm). In yet other examples, the vertical axis offset  780  may be any value in a range between 0.1 in. (2.54 mm) and 2.0 in. (50.8 mm). The vertical axis offset  780  may therefore wholly or in part counteract the difference in exposure between the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2 . 
     In some embodiments, the first rolling cutting structure  712 - 1  may have the same wheel diameter (e.g., wheel diameter  220  of  FIG. 2-2 ) as the second rolling cutting structure  712 - 2 . In other embodiments, the first rolling cutting structure  712 - 1  may have a different wheel diameter as the second rolling cutting structure  712 - 2 . In some embodiments, the second rolling cutting structures  712 - 2  may have a wheel diameter that is a percent of the first rolling cutting structure  712 - 1 . In some embodiments, the percentage may be in a range having an upper value, a lower value, or upper and lower values including any of 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130%, 140%, 150%, or any value therebetween. For example, the percentage may be greater than 50%. In another example, the percentage may be less than 150%. In yet other examples, the percentage may be any value in a range between 50% and 150%. Changing the wheel diameter may therefore wholly or in part counteract the difference in exposure between the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2 . 
       FIG. 7-4  is a bottom-up cross-sectional view of the bit  710  of  FIGS. 7-1, 7-2 , and  7 - 3 . In some embodiments, the first journal axle axis  755 - 1  and the second journal axle axis  755 - 2  may be coaxial, or may share a common axis. In other embodiments, the first journal axle axis  755 - 1  may be offset from the second journal axle axis  755 - 2  with a radial axis offset  782 . In some embodiments, the radial axis offset  782  may be in a range having an upper value, a lower value, or upper and lower values including any of 0.1 in. (2.54 mm), 0.2 in. (5.08 mm), 0.3 in. (7.62 mm), 0.4 in. (10.16 mm), 0.5 in. (12.70 mm), 0.6 in. (15.24 mm), 0.7 in. (17.78 mm), 0.8 in. (20.32 mm), 0.9 in. (22.86 mm), 1.0 in. (25.40 mm), or any value therebetween. For example, the radial axis offset  782  may be greater than 0.1 in. (2.54 mm). In another example, the radial axis offset  782  may be less than 1.0 in. (25.40 mm). In yet other examples, the radial axis offset  782  may be any value in a range between 0.1 in. (2.54 mm) and 1.0 in. (25.40 mm). The radial axis offset  782  may therefore wholly or in part counteract the difference in exposure between the first rolling cutting structure  712 - 1  and the second rolling cutting structure  712 - 2 . While described in reference to  FIG. 7-4 , this offset difference may also apply to the other embodiments described herein, where the rolling cutting structures are located on different blades. 
       FIG. 7-5  is an embodiment of a cutting profile  775 , according to at least one embodiment of the present disclosure. Different regions along the cutting profile  775  may be primarily cut by different cutting elements. In other words, different cutting elements may have the highest exposure along different regions of the cutting profile  775 . In the embodiment shown in  FIG. 7-5 , a central first region  777  may be cut primarily by secondary cutting elements on the rolling cutting structures (e.g., the secondary cutting elements  717  of the rolling cutting structures  712 - 1 ,  712 - 2  shown on  FIG. 7-2 ). The secondary cutting elements may be added to a rolling cutting structure specifically to cut this central first region  777 , because otherwise the primary cutting elements (e.g., the first cutting elements  716 - 1  of  FIG. 7-3 ) may not cut, or may not cut sufficiently, the central first region  777 . 
     A second region  779  may be cut primarily by primary cutting elements of a second rolling cutting structure (e.g., the first cutting elements  716 - 1  of the second rolling cutting structure  712 - 2  of  FIG. 7-3 ). A third region  781  may be cut primarily by primary cutting elements of a first rolling cutting structure (e.g., the primary cutting elements  716 - 1  of the first rolling cutting structure  712 - 1  of  FIG. 7-3 .). As may be seen, in some embodiments, the third region  781  may include the “nose” region of a bit. Thus, the primary cutting elements of the first rolling cutting structure may remove the largest amount of material. An outermost fourth region  783  may be cut by fixed cutting elements of a fixed cutting structure (e.g., fixed cutting structure  730  of  FIG. 7-2 ). This outermost fourth region  783  may include the “shoulder” and/or the “gauge” region of a bit. As discussed above with  FIG. 3-4 , the nose region  781  may be cut by fixed cutting elements of the fixed cutting structure  730  and/or by the primary cutting elements of the rolling cutting structures  712 . 
     As may be seen, one primary rolling cutting structure may have the largest cutting load. However, the remaining cutting structures may support the rolling cutting structure. Specifically, the remaining cutting structures may primarily cut sections of the formation that the primary rolling cutting structure may not be able to sufficiently reach. 
       FIG. 8  is a method chart for a method  884  of forming a drill bit, according to at least one embodiment of the present disclosure. The method  884  may include selecting a bit body at  886 . Selecting the bit body may include selecting a bit body having a specific geometry. The geometry may include one or more fixed cutting structures, one or more rolling cutting structures, and so forth. In some embodiments, selecting the bit body may include forming the bit body. For example, the bit body may be cast, machined, or manufactured using additive manufacturing. The bit body may be a matrix body, a steel body, an additively manufactured body, or any combination thereof. In other examples, selecting the bit body may include selecting the design of a bit body and manufacturing the bit body or having a third party manufacture the bit body. 
     The method  884  may include installing a rolling cutting structure at  888 . Installing the rolling cutting structure may include inserting the rolling cutting structure into a rolling cavity in the bit body and inserting a journal into a journal cavity in the bit body. Installing the rolling cutting structure may also include arranging with the journal any seals, sleeves, washers, or bearings, or any combination thereof. As described above, the journal and the sleeves may be selected and installed to adjust the exposure of the cutting elements of the rolling cutting structure. 
     The method may further include securing the rolling cutting structure to the bit body at  890 . Securing the rolling cutting structure to the bit body may include securing the journal to the bit body. Securing the journal to the bit body may include securing the journal to the trailing edge of a blade. Securing the journal to the bit body may further include securing the journal to a support leg of the blade and the main body of the blade. 
     The embodiments of the hybrid bit have been primarily described with reference to wellbore drilling operations; the hybrid bit described herein may be used in applications other than the drilling of a wellbore. In other embodiments, hybrid bits according to the present disclosure may be used outside a wellbore or other downhole environment used for the exploration or production of natural resources. For instance, hybrid bits of the present disclosure may be used in a borehole used for placement of utility lines. Accordingly, the terms “wellbore,” “borehole” and the like should not be interpreted to limit tools, systems, assemblies, or methods of the present disclosure to any particular industry, field, or environment. 
     One or more specific embodiments of the present disclosure are described herein. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, not all features of an actual embodiment may be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous embodiment-specific decisions will be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one embodiment to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     The articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements in the preceding descriptions. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. For example, any element described in relation to an embodiment herein may be combinable with any element of any other embodiment described herein. Numbers, percentages, ratios, or other values stated herein are intended to include that value, and also other values that are “about” or “approximately” the stated value, as would be appreciated by one of ordinary skill in the art encompassed by embodiments of the present disclosure. A stated value should therefore be interpreted broadly enough to encompass values that are at least close enough to the stated value to perform a desired function or achieve a desired result. The stated values include at least the variation to be expected in a suitable manufacturing or production process, and may include values that are within 5%, within 1%, within 0.1%, or within 0.01% of a stated value. 
     A person having ordinary skill in the art should realize in view of the present disclosure that equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations may be made to embodiments disclosed herein without departing from the spirit and scope of the present disclosure. Equivalent constructions, including functional “means-plus-function” clauses are intended to cover the structures described herein as performing the recited function, including both structural equivalents that operate in the same manner, and equivalent structures that provide the same function. It is the express intention of the applicant not to invoke means-plus-function or other functional claiming for any claim except for those in which the words ‘means for’ appear together with an associated function. Each addition, deletion, and modification to the embodiments that falls within the meaning and scope of the claims is to be embraced by the claims. 
     The terms “approximately,” “about,” and “substantially” as used herein represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” and “substantially” may refer to an amount that is within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of a stated amount. Further, it should be understood that any directions or reference frames in the preceding description are merely relative directions or movements. For example, any references to “up” and “down” or “above” or “below” are merely descriptive of the relative position or movement of the related elements. 
     The present disclosure may be embodied in other specific forms without departing from its spirit or characteristics. The described embodiments are to be considered as illustrative and not restrictive. Changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.