Patent Publication Number: US-11035177-B2

Title: Shaped cutters

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure generally relates to cutting elements for use on rotary drill bits for drilling subterranean formations. More specifically, the present disclosure relates to cutting elements having a shaped upper surface including at least one spoke for cutting and/or failing subterranean formations during drilling. The present disclosure also relates to drill bits incorporating one or more of such cutting elements. 
     BACKGROUND 
     Rotary drill bits are often used to drill a variety of subterranean formations. Different types of rotary drill bits are known in the art including, e.g., fixed-cutter bits (which are often referred to as “drag bits”), rolling-cutter bits (which are often referred to in the art as “rock bits”), diamond-impregnated bits, and hybrid bits, e.g., both fixed cutters and rolling cutters. Generally, rotary drill bits include cutting elements attached to the bit body. During operation, the drill bit is rotated and advanced into the subterranean formation. As the drill bit rotates, the cutting elements cut, crush, shear, and/or abrade away the formation material to form a wellbore in the subterranean formations. 
     Many cutting elements having superhard cutting faces suffer from cracking, spalling, chipping and partial fracturing of the cutting surface at a region of the cutting element subjected to the highest load during drilling, e.g., the critical region. The critical region encompasses the portion of the cutting surface that makes contact with the subterranean formation during drilling. The critical region is subjected to high magnitude stresses from dynamic normal loading, and shear loadings imposed on the cutting face of the cutting element during drilling. Because cutting elements are typically inserted into a drag bit at a rake angle, the critical region includes a portion of the superhard surface near and including a portion of the layer&#39;s circumferential edge that makes contact with the subterranean formations during drilling. 
     The high magnitude stresses at the critical region alone or in combination with other factors, such as residual thermal stresses, can result in the initiation and growth of cracks across the cutting face of cutting elements. Cracks may cause the separation of a portion of the cutting face, rendering the cutting element ineffective or resulting in cutting element failure. When this happens, drilling operations may have to cease to allow for recovery of the drag bit and for replacement of the ineffective or failed cutting element. The high stresses, particularly shear stresses, can also result in delamination of the ultrahard layer at the interface. 
     Thus, the need exists for cutting elements that can withstand high loading at the critical region imposed during drilling to improve operating life. Additionally, the need exists for cutting elements that cut efficiently at designed speed and loading conditions to regulate the amount of cutting load in changing formations. The need also exists for improved drill bit stability. 
     BRIEF SUMMARY 
     In some embodiments, the present disclosure relates to a cutting element, the cutting element comprising: a substantially cylindrical substrate; a superabrasive table positioned on the cylindrical substrate, the superabrasive table comprising: a cutting face having a substantially planar portion surrounding a central recess, the planar portion extending laterally to an outer circumferential edge; and at least one spoke disposed on the cutting face, the spoke extending radially from a periphery of the recess to the outer circumferential edge. In some aspects, each spoke comprises an upper surface having an interior region adjacent the periphery of the recess and an outer region adjacent the edge of the cutting face, wherein the upper surface has an upper surface width that decreases from the interior region to the outer region. In some aspects, the spoke is raised in relation to the planar portion of the cutting face. In some aspects, the spoke comprises an interior region adjacent the periphery of the recess and an outer region adjacent the edge of the cutting face, wherein the spoke has a height that increases from the interior region to the outer region, and wherein the spoke has a maximum height at the outer region. In some aspects, the spoke comprises an interior region adjacent the periphery of the recess, an outer region adjacent the edge of the cutting face, and an upper lateral spoke surface extending therebetween, wherein the spoke comprises sidewalls on opposing sides of the upper lateral spoke surface, each of the sidewalls extending from the upper lateral spoke surface to the planar portion of the cutting face. In some aspects, each of the sidewalls are transverse relative to the upper lateral spoke surface of the spoke and the planar portion of the cutting face, wherein each sidewall increases in height from the interior region to the outer region. In some aspects, the cutting element comprises at least four spokes equidistantly spaced on the cutting face, wherein the planar portion is divided into four separate planar portions, each pair of adjacent spokes being separated by a respective planar portion. In some aspects, the recess is substantially circular and is defined by a laterally extending convex surface and a longitudinally extending circumferential side wall. In some aspects, the superabrasive table comprises a chamfered region between the edge of the cutting face and a sidewall of the cylindrical substrate. 
     In some embodiments, the present disclosure relates to a cutting element, the cutting element comprising: a substantially cylindrical substrate; a superabrasive table positioned on the cylindrical substrate, the superabrasive table comprising: a cutting face having a substantially planar central region and an outer circumferential cutting edge; a plurality of spokes extending radially outward from the central region to the edge of the cutting face, wherein each spoke comprises an interior region adjacent the central region, an outer region adjacent the edge of the cutting face, and an upper surface extending therebetween, wherein a ratio of an upper surface width at the interior region to the upper surface width at the outer region ranges from 0.5:1 to 2:1; and a plurality of depressions, each depression extending between adjacent spokes and from a periphery of the central region to the outer circumferential cutting edge of the cutting face. In some aspects, the upper surface of each spoke is substantially co-planar and continuous with the central region. In some aspects, the upper surface of each spoke has a width that is substantially constant from the interior region to the outer region. In some aspects, the upper surface of each spoke has a width that decreases from the interior region to the outer region. In some aspects, each depression has a depth that increases from an interior radial region to an outer radial region, wherein each depression merges with the cutting edge. In some aspects, each depression merges with a portion of one or more spokes at the interior region adjacent the central region. In some aspects, the cutting face does not include a substantially planar outer lateral circumferential portion adjacent the cutting edge of the cutting face. In some aspects, each spoke increases in height from the interior region to the outer region, wherein the spoke has a maximum height at the outer region. In some aspects, each spoke includes sidewalls on opposing sides of the upper surface, each of the sidewalls extending from the upper surface to the depression. In some aspects, each sidewall extends from the upper surface to the depression of an associated spoke at a transverse angle. In some aspects, the cutting element comprises at least four spokes equidistantly spaced on the cutting face, wherein each of the at least four spokes are symmetrically arranged on the cutting face, wherein each of the at least four spokes are continuous and co-planar with the central region. In some aspects, the upper surface has a minimum upper surface width in an intermediate region between the central region and the outer region. In some aspects, an interior region of each depression forms an angle ranging from 45° to 180° between adjacent spokes. In some aspects, each depression has a depth that is constant or decreases from an interior radial region to an outer radial region. In some aspects, the cutting face includes a substantially planar outer lateral circumferential portion adjacent the cutting edge of the cutting face. In some aspects, each spoke comprises an interior region adjacent the central region, an outer region adjacent the edge of the cutting face, and an upper surface extending therebetween, wherein the upper surface has a minimum upper surface width in an intermediate region between the central region and the outer region. 
     In some embodiments, the present disclosure relates to a cutting element, the cutting element comprising a superabrasive table positioned on the cylindrical substrate, the superabrasive table comprising: an asymmetric cutting face having a substantially planar central region and an outer circumferential cutting edge; a plurality of spokes extending radially outward from the central region to the edge of the cutting face, each spoke comprises an interior region adjacent the central region, an outer region adjacent the cutting edge of the cutting face, and an upper surface extending therebetween, wherein each spoke includes sidewalls on opposing sides of the upper surface; and a plurality of depressions, each depression extending between adjacent spokes and from a periphery of the central region to the outer circumferential cutting edge of the cutting face. In some aspects, each spoke has a leading sidewall and a trailing sidewall and, when taken in the clockwise direction, the leading sidewall has a shorter length than the trailing sidewall. In some aspects, each spoke has a leading sidewall and a trailing sidewall and, when taken in the clockwise direction, the leading sidewall has a longer length than the trailing sidewall. In some aspects, the sidewalls of each of the spokes are not mirror images of each other. In some aspects, at least one of the sidewalls is convex. In some aspects, at least one of the sidewalls is concave. In some aspects, the upper surface of each spoke is substantially co-planar continuous with the central region. In some aspects, the cutting element comprises at least four spokes spaced apart on the cutting face, wherein each of the at least four spokes are continuous and co-planar with the central region. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of a rotary drill bit including cutting elements according to embodiments of the present disclosure. 
         FIG. 2A  shows a perspective view of a cutting element according to embodiments of the present disclosure. 
         FIG. 2B  shows a top plan view of the cutting element of  FIG. 2A  according to embodiments of the present disclosure. 
         FIG. 2C  shows a partial cross-sectional view of a superabrasive table of the cutting element of  FIG. 2A  along line A showing a profile of a radial spoke relative to planar depression on the cutting face, according to embodiments of the present disclosure. 
         FIG. 3  shows a perspective view of the superabrasive table of a cutting element having a central recess according to some embodiments of the present disclosure. 
         FIG. 4  shows a perspective view of the superabrasive table of the cutting element having a planar cutting surface according to embodiments of the present disclosure. 
         FIG. 5A  shows a perspective view of the superabrasive table of the cutting element having a planar cutting surface according to embodiments of the present disclosure. 
         FIG. 5B  shows a top plan view of the cutting element of  FIG. 5A  according to embodiments of the present disclosure. 
         FIG. 6  shows a perspective view of a superabrasive table of a cutting element having a planar cutting surface according to embodiments of the present disclosure. 
         FIG. 7  shows a perspective view of a superabrasive table of a cutting element having a planar cutting surface according to embodiments of the present disclosure. 
         FIG. 8  shows a perspective view of a superabrasive table of a cutting element having a planar cutting surface according to embodiments of the present disclosure. 
         FIG. 9  shows a perspective view of a superabrasive table of a cutting element having three radially extending spokes according to embodiments of the present disclosure. 
         FIG. 10  shows a perspective view of a superabrasive table of a cutting element having depressed regions according to embodiments of the present disclosure. 
         FIG. 11  shows a perspective view of a superabrasive table of a cutting element having depressed regions according to embodiments of the present disclosure. 
         FIG. 12  shows a perspective view of a superabrasive table of a cutting element having an asymmetric planar cutting surface according to embodiments of the present disclosure. 
         FIG. 13  shows a perspective view of a superabrasive table of a cutting element having an asymmetric planar cutting surface according to embodiments of the present disclosure. 
         FIG. 14  shows a perspective view of a superabrasive table of a cutting element having an asymmetric planar cutting surface according to embodiments of the present disclosure. 
         FIG. 15  shows a perspective view of a superabrasive table of a cutting element having an asymmetric planar cutting surface according to embodiments of the present disclosure. 
         FIG. 16  shows a perspective view of a superabrasive table of a cutting element having an asymmetric planar cutting surface according to embodiments of the present disclosure. 
         FIG. 17  shows performance characteristics of shaped cutter elements according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Introduction 
     The present disclosure relates to cutting elements having shaped cutting surfaces that can withstand high loading at the critical region during drilling thereby enhancing operating life. The shaped cutting elements provide a relatively high rate of penetration and increased depth of drilling, while at the same time minimizing the effects of wear and the tendency for breakage of the cutting element. In particular, the orientation and placement of the individual cutting elements on the rotary drill bit can improve the rate of penetration, speed, and loading conditions, and can compensate for the amount of cutting load in changing formations. For example, the cutter profile, e.g., the exposure of the cutting element as well as the back rake and side rake of the cutting element on the rotary drill bit, have been found to significantly contribute to increased drilling depth before failure of one or more cutting elements. Additionally, the shaped cutter surfaces have substantially improved impact resistance, abrasion resistance and hydraulic efficiency during drilling. 
     The inventors have found that cutting elements with sharp cutting edges or small back rake angles provide a high rate of penetration (“ROP”), but are often subject to instability and are susceptible to chipping, cracking or partial fracturing when subjected to high forces normal to the working surface. For example, large forces can be generated when the cutter digs or gouges deep into a formation or when sudden changes in formation hardness produce sudden impact loads. Small back rake angles also tend to exhibit less delamination resistance when subjected to shear load. Cutters with large back rake angles, in contrast, are often subjected to heavy wear, abrasion and shear forces resulting in chipping, spalling, and delaminating due to excessive downward force or “weight on bit” (WOB) required to obtain reasonable ROP. Thick ultrahard layers may provide abrasion wear, but are often susceptible to cracking, spalling, and delaminating as a result of residual thermal stresses associated with forming thick ultrahard layers on the substrate. The susceptibility to such deterioration and failure mechanisms is accelerated when combined with excessive load stresses. 
     The inventors have discovered that using cutting elements with shaped cutting surfaces, as described herein, can better withstand high loading at the critical region during drilling to enhance operating life. The cutters with shaped working surfaces can cut efficiently at designed speed, penetration, and loading conditions, and can compensate for the amount of cutting load in changing formations. The shaped cutting surfaces have been found to contribute to reduced chipping, cracking or partial fracturing when subjected to high forces normal to the working surface in response to increased cutting depth. Additionally, the inventors have found that the shaped cutter surfaces provide efficient chip removal and increased stability to provide selectable cutting characteristics for different locations on the rotary drill bit. 
     As used herein, the phrase “rotary drill bits” or “drill bit” refers generally to any type of drilling tool, e.g., drag bits, roller cone bits, hybrid bits (e.g., including both fixed cutters and roller elements), coring bits, percussion bits, bi-center bits, reamers, and other so-called “hole-opening” tools. It is contemplated that the cutting elements described herein can be used in conjunction with any type of rotary drill bit that is used to cut or otherwise remove formation material to form or enlarge a bore in the formation. 
     Rotary Drill Bit 
       FIG. 1  illustrates an example of a rotary drill bit  100  according to embodiments of the present disclosure. The rotary drill bit  100  of  FIG. 1  is intended to be a representative example of drill bits, e.g., drag bits, for drilling formations. The rotary drill bit  100  is designed to be rotated around its central axis  102 . The drill bit comprises a bit body  104  connected to a shank  106  having a tapered threaded coupling  108  for connecting the bit to a drill string (not shown). The drill bit may further include a bit breaker surface  111  for cooperating with a wrench to tighten and loosen the coupling to the drill string. The exterior surface of the bit body  104  is intended to face generally in the direction of boring and is referred to as bit face. The face generally lies in a plane perpendicular to the central axis  102  of the bit. The bit body  104  is not limited to any particular material. In some embodiments, the bit body  104  comprises steel or a matrix material, e.g., powdered tungsten carbide cemented by metal binder. 
     During drilling operation, the rotary drill bit  100  may be coupled to the drill string. As the rotary drill bit  100  is rotated within the wellbore via the drill string, drilling fluid may be pumped down the drill string, through the internal fluid plenum and fluid passageways within the bit body  104  of the rotary drill bit  100 , and out from the rotary drill bit  100  through nozzles  117 . Formation cuttings generated by the cutting elements of the bit body  104  may be carried with the drilling fluid through the fluid courses (e.g., “junk slots”), around the rotary drill bit  100 , and back up the wellbore through the annular space within the wellbore outside the drill string. 
     The bit body  104  may include a plurality of raised blades  110  that extend from the face of the bit body  104 . In some embodiments, the plurality of blades  110  extend radially along the bit face and are circumferentially spaced structures extending along the leading end or formation engaging portion of the bit body  104 . Each blade  110  may extend generally in a radial direction, outwardly to the periphery of the bit body  104 . For example, the blades  110  may generally extend from the cone region proximate the longitudinal axis, or central axis  102 , of the bit, upwardly to the gage region, or maximum drill diameter of bit. In some embodiments, the blades  110  are substantially equally spaced around the central axis  102  of the bit and each blade  110  sweeps or curves backwardly in the direction of rotation indicated by arrow  115 . 
     The bit body  104  further includes a plurality of superabrasive cutting elements  112 , e.g., polycrystalline diamond compact (“PDC”) cutting elements, disposed on radially outward facing surfaces of each of the blades  110 . For example, a plurality of discrete cutting elements  112  may be mounted on each blade  110 . Each discrete cutting element  112  may be disposed within a recess or pocket in each blade  110 . The cutting elements  112  may be mounted to a rotary drill bit  100  either by press-fitting or otherwise locking the stud (e.g., substrate portion of cutting element) of the cutting elements  112  into a receptacle on a drag bit, or by brazing a portion of the cutting elements  112  directly into a preformed pocket, socket or other receptacle on the face of a bit body  104 . 
     Cutting elements  112  used in rotary drill bits are often PDC cutting elements. It has been known in the art that PDC cutters perform well on drag bits. PDC cutting elements include a polycrystalline diamond (PCD) material, which may be characterized as a superabrasive or superhard material. Such polycrystalline diamond materials are formed by sintering and bonding together small diamond grains (e.g., diamond crystals), under conditions of high temperature and high pressure, in the presence of a catalyst material to form polycrystalline diamond. 
     In the rotary drill bit  100 , the cutting elements  112  may be placed along the forward (in the direction of intended rotation) side of the blades  110 , with their working surfaces facing generally in the forward direction for shearing the earth formation when the rotary drill bit  100  is rotated about its central axis  102 . In some embodiments, the blade  110  may comprise one or more rows of cutting elements  112  disposed on the blade  110 . For example, the blade  110  may comprise a first row of primary cutters and a second row of backup cutters. A plurality of primary cutting elements may be mounted side-by-side along each blade. The secondary cutting elements may be mounted rearwardly from the primary cutters on the blade  110 . The secondary cutting elements may rotationally follow the primary cutters at selected back rake and side rake angle. For example, the secondary cutting elements may be spaced rearwardly from the primary cutting elements to cut or abrade a kerf region formed between adjacent primary cutters. In some embodiments, at least one of the cutting elements, e.g., a secondary cutter, is clocked relative to a kerf region formed by a rotationally preceding cutter, e.g., a primary cutter. As used herein, clocked refers to aligning a spoke of the cutting element with a kerf region. 
     In some aspects, the secondary cutting elements may be mounted on another blade  110  from the primary cutters. Although the figures only show a few secondary cutting elements mounted on each blade  110 , any number of the primary cutting elements may be provided with an associated secondary cutting element. As well known in the art, cutting elements  112  are radially spaced such that the groove or kerf formed by cutting elements  112  overlaps to a degree with kerfs formed by one or more cutting elements  112  in other rows. 
     In some aspects, the secondary cutting element may lie at the same radial distance from the axis of rotation of the bit as its associated primary cutting element. In the example shown in  FIG. 1 , the cutters are arranged along blades to form a structure cutting or gouging the formation and then pushing the resulting debris into the drilling fluid which exits the rotary drill bit  100  through the nozzles  117 . The drilling fluid in turn transports the debris or cuttings uphole to the surface. 
     In some embodiments, the cutting elements  112  may comprises PDC cutters. However, in other embodiments, not all of the cutters need to be PDC cutters. The PDC cutters in this example have a working surface made primarily of super hard, polycrystalline diamond, or the like, supported by a substrate that forms a mounting stud for placement in a pocket formed in the blade  110 . In some embodiments, each of the PDC cutters is fabricated discretely and then mounted—by brazing, press fitting, or otherwise into pockets formed on bit. This example of a drill bit includes gage pads  114 . In some applications, the gauge pads of drill bits such as rotary drill bit  100  can include an insert of thermally stable, sintered polycrystalline diamond (TSP). 
     Generally, each blade  110  includes a cone region, a nose region, a shoulder region, and a gage region. Fluid ports are disposed about the face of the bit body  104  and are in fluid communication with at least one interior passage provided in the interior of bit body. In some aspects, fluid ports include nozzles  117  disposed therein to better control the expulsion of drilling fluid from bit body into fluid courses and junk slots in order to facilitate the cooling of cutters on bit and the flushing of formation cuttings up the borehole toward the surface when bit is in operation. 
     In some embodiments, the cutting elements  112  are embedded or mounted on the blades at a selected back rake and a selected side rake depending on their location on the blade  110 . The cutting elements  112  may be strategically located on the respective blades  110  in desired forward sweep, back rake and side rake configurations to facilitate optimum cutting efficiency and channeling of drilling fluid pumped through the rotary drill bit  100  around the blades  110  and cutting elements  112  to clear the cutting elements  112  of formation cuttings in an optimal manner. 
     As mentioned, the back rake and side rake of each cutting element may be dependent on the location of the cutting element on the blade. In some aspects, the back rake of the cutting element(s) in the cone region ranges from 5° to 45°, e.g., from 10° to 40°, from 15° to 35°, or from 20° to 30°. In terms of upper limits, the back rake of the cutting element(s) in the cone region is less than 45°, e.g., less than 40°, less than 30°, or less than 20°. In terms of lower limits, the back rake of the cutting element(s) in the cone region is greater than 5°, e.g., greater than 10°, greater than 15°, or greater than 18°. In some aspects, the side rake of the cutting element(s) in the cone region ranges from 0° to 10°, e.g., from 1° to 9°, from 2° to 8°, or from 4° to 6°. In terms of upper limits, the side rake of the cutting element(s) in the cone region is less than 10°, e.g., less than 8°, less than 6°, or less than 5°. In terms of lower limits, the side rake of the cutting element(s) in the cone region is greater than 0°, e.g., greater than 1°, greater than 2°, or greater than 4°. 
     In some aspects, the back rake of the cutting element(s) in the nose region ranges from 10° to 30°, e.g., from 12° to 28°, from 15° to 25°, or from 18° to 22°. In terms of upper limits, the back rake of the cutting element(s) in the nose region is less than 30°, e.g., less than 28°, less than 25°, or less than 22°. In terms of lower limits, the back rake of the cutting element(s) in the nose region is greater than 10°, e.g., greater than 12°, greater than 15°, or greater than 18°. In some aspects, the side rake of the cutting element(s) in the nose region ranges from 5° to 20°, e.g., from 6° to 18°, from 7° to 16°, or from 8° to 14°. In terms of upper limits, the side rake of the cutting element(s) in the nose region is less than 20°, e.g., less than 18°, less than 15°, or less than 12°. In terms of lower limits, the side rake of the cutting element(s) in the nose region is greater than 5°, e.g., greater than 6°, greater than 7°, or greater than 8°. 
     In some aspects, the back rake of the cutting element(s) in the shoulder region ranges from 10° to 30°, e.g., from 12° to 28°, from 15° to 25°, or from 18° to 22°. In terms of upper limits, the back rake of the cutting element(s) in the shoulder region is less than 30°, e.g., less than 28°, less than 25°, or less than 22°. In terms of lower limits, the back rake of the cutting element(s) in the shoulder region is greater than 10°, e.g., greater than 12°, greater than 15°, or greater than 18°. In some aspects, the side rake of the cutting element(s) in the shoulder region ranges from 5° to 20°, e.g., from 6° to 18°, from 7° to 16°, or from 8° to 14°. In terms of upper limits, the side rake of the cutting element(s) in the shoulder region is less than 20°, e.g., less than 18°, less than 15°, or less than 12°. In terms of lower limits, the side rake of the cutting element(s) in the shoulder region is greater than 5°, e.g., greater than 6°, greater than 7°, or greater than 8°. 
     In some aspects, the back rake of the cutting element(s) in the gage region ranges from 15° to 50°, e.g., from 20° to 45°, from 25° to 40°, or from 30° to 35°. In terms of upper limits, the back rake of the cutting element(s) in the gage region is less than 50°, e.g., less than 45°, less than 40°, or less than 35°. In terms of lower limits, the back rake of the cutting element(s) in the gage region is greater than 15°, e.g., greater than 20°, greater than 25°, or greater than 30°. In some aspects, the side rake of the cutting element(s) in the gage region ranges from 0° to 10°, e.g., from 1° to 9°, from 2° to 8°, or from 4° to 6°. In terms of upper limits, the side rake of the cutting element(s) in the gage region is less than 10°, e.g., less than 8°, less than 6°, or less than 5°. In terms of lower limits, the side rake of the cutting element(s) in the gage region is greater than 0°, e.g., greater than 1°, greater than 2°, or greater than 4°. 
     The cutting elements  112  may have cutting faces having the same general shape, or the cutting elements  112  may have various shapes. The cutting faces of the elements may also differ in size according to their position on the blade  110  of the rotary drill bit  100 . Additionally, cutting elements  112  may have differing cutting profiles, e.g., exposure heights, such that those elements extending further from the bit face are more exposed (e.g., high profile) to the formation material than those which are mounted at a relatively lower height (e.g., low profile) from the bit face. In some embodiments, cutting elements have a limited amount of exposure generally perpendicular to the selected portion of the formation-facing surface in which the superabrasive cutter is secured to control the effective depth-of-cut of at least one superabrasive cutter into a formation when the bit is engaging a formation during drilling. 
     In some embodiments, the cutting elements  112  having the smallest cutting face, as measured by surface contact surface area, will generally be mounted so as to have the greatest exposure to the formation, while the cutting elements having the largest cutting face will have the least exposure to the formation. This arrangement increases the stability of the bit by creating relatively tall and sharply tapered ridges between the kerfs which provide the side forces helpful in resisting bit vibration. The most exposed cutters may either have more or less negative back rake relative to the other cutters as dependent upon the type of formation being cut. 
     Shaped Cutters 
       FIG. 2A  is a perspective view of a cutting element  200  according to one embodiment of the present disclosure. The cutting element  200  includes a cutting element substrate  202  having a superabrasive table  204  thereon. The superabrasive table  204  may comprise a superabrasive material, e.g., a PCD material, having a cutting face  206 . In some aspects, superabrasive materials may comprise natural diamond, synthetic diamond, cubic boron nitride, diamond-like carbon materials, or combinations thereof. In some aspects, the cutting element  200  includes a diamond table  204 . The cutting element substrate  202  may have a generally cylindrical shape as shown in  FIG. 2A . 
     The superabrasive table  204  may be formed or mounted on the cutting element substrate  202 . In some aspects, the cutting element substrate  202  and the superabrasive table  204  may be distinct and separate components. That is, the cutting element substrate  202  and the superabrasive table  204  may separately formed and subsequently attached together. The cutting element substrate  202  may comprise a material that is relatively hard and resistant to wear, or may comprise the same material as the superabrasive table  204 . For example, the cutting element substrate  202  may comprise a ceramic-metal composite material, e.g., cermet. In some aspects, the cutting element substrate  202  may include a cemented carbide material, such as a cemented tungsten carbide material, in which tungsten carbide particles are cemented together in a metallic binder material. The metallic binder material may include, for example, cobalt, nickel, iron, or alloys and mixtures thereof. 
     The cutting element  200  may be a PDC cutter. The PDC cutter may be formed by placing a substrate, e.g., a sintered carbide substrate, into the container of a press. A mixture of diamond grains or diamond grains and catalyst binder is placed atop the substrate and treated under high pressure, high temperature conditions. In doing so, metal binder migrates from the substrate and passes through the diamond grains to promote intergrowth between the diamond grains. As a result, the diamond grains become bonded to each other to form the diamond layer, and the diamond layer is in turn integrally bonded to the substrate. The substrate often comprises a metal-carbide composite material, such as tungsten carbide-cobalt. The deposited diamond layer is often referred to as the “diamond table” or “abrasive layer.” 
     In some aspects, the cutting element substrate  202  may comprise two layers, including a layer immediately supporting the superabrasive table  204 , which may be formed and bonded to another piece of like diameter. In some aspects, the layers of the superabrasive table  204  may comprise the same material or may comprise different materials. In any case, the cutting elements  200  may be secured in pockets on blades  110 , e.g., by brazing, as depicted in  FIG. 1 . 
     An interface  208  may be defined between the cutting element substrate  202  and superabrasive table  204 . The interface  208  between the cutting element substrate  202  and superabrasive table  204  may be substantially planar. The term “substantially planar” should also be understood to encompass cutting elements  200  having grooved, ridged or other non-planar interfaces between the superabrasive table  204  and the supporting substrate  202 . For example, the surface of the cutting element substrate  202  in contact with the superabrasive table  204  may include one or more concave or convex portions. In this example, the surface of the superabrasive table  204  that contacts the surface of the cutting element substrate  202  may include a corresponding concave or convex portion to form a press-fit. 
     In some aspects, the superabrasive table  204  may have a chamfered edge  210 . The chamfered edge  210  may be interposed between the cutting face  206  and the side of the superabrasive table  204 . The chamfered edge  210  of the superabrasive table  204  shown in  FIG. 2A  has a single chamfer surface  212 . In some embodiments, the chamfered edge  210  also may have additional chamfer surfaces. The additional chamfer surfaces may be oriented at chamfer angles that differ from the chamfer angle of the chamfer surface  212 . In some embodiments, one or more edge portions, e.g., arcuate edges, may be employed in lieu of, or in addition to, one or more chamfered surfaces at a peripheral edge of the superabrasive table  204 . 
     The superabrasive table  204  positioned on the cutting element substrate  202  includes a cutting face  206  distal to the cutting element substrate  202 . The cutting face  206  includes at least one substantially planar portion  214  surrounding or adjacent to a recess  216 . As shown in  FIG. 2B , the recess  216  may be located at central region of the cutting face  206 , e.g., at or proximate to the longitudinal centerline of the cutting element  200 . The planar portion  214  extends laterally from the periphery of the recess  216  to an outer circumferential edge  218  of the cutting face  206 . The recess  216  can be a recessed center region that reduces cross-face cracking. 
     In some aspects, the planar portion  214  is transverse to the longitudinal centerline of the cutting element  200 . For example,  FIG. 2C  shows a cross-sectional profile of a planar portion  214  relative to the recess  216 . The planar portion  214  may extend radially from a region  215  adjacent the central recess  216  at a sloped downward angle to the outer circumferential edge  218  of the cutting face  206 . In some aspects, the planar portion  214  may have a maximum height at a region  215  adjacent the central recess  216 . The planar portion  214  may be at an angle ranging from 0° to 90°, relative to the centerline of the cutting element, e.g., from 5° to 80°, from 10° to 70°, from 20° to 60°, or from 30° to 50°. In some aspects, the planar portion  214  may form a 90° angle with the centerline of the cutting element. In some aspects, the planar portion  214  may have an arcuate radial cross-section defined in the cutting face  206 . 
     The planar portions  214  may be positioned proximate to a peripheral edge of the cutting element  200 . In some aspects, the plurality of planar portions  214  may be proximate to the chamfer surface  212 , and may extend generally radially from proximate the peripheral edge to a central recess region  216  of the cutting element  200  proximate a longitudinal central axis of the cutting element  200 . Each planar portion  214  may be defined by an arcuate cross-section having a primary surface with a cross-sectional dimension defined by a radius R 1 . 
       FIGS. 2A and 2B  each show at least one radially extending spoke  220  disposed on the cutting face  206  of the superabrasive table  204 . In some embodiments, the planar portion  214  may be segmented by the spokes  220  into a plurality of planar portions  214 . The spokes  220  may extend radially from a periphery of the central recess  216  to the outer circumferential edge  218 . The spoke  220  may be formed of integral regions of the superabrasive table  204  and may comprise the same superabrasive material as the superabrasive table  204 . 
     The radially extending spokes  220  may segment the planar portion  214  into generally annular planar portions  214  having an arcuate radial cross-section defined in the cutting face  206  of the cutting element  200 . For example, the cutting face  206  of the cutting element  200  may include at least four radially extending spokes  220  equidistantly spaced on the cutting face  206 . In this embodiment, the planar portion  214  is divided into four separate planar portions  214 . In particular,  FIGS. 2A and 2B  show that each pair of adjacent spokes  220  are separated by a respective planar portion  214 . 
     Each spoke  220  may traverse at least a portion of the planar portion  214 . That is, each spoke  220  may extend at least partially between the outer periphery of the recess  216  (i.e., a region at or proximate the central axis) to an outer circumferential edge  218  of the cutting face  206 . For example, each spoke  220  may traverse the entire planar portion  214  and extend from adjacent the central recess  216  to the outer circumferential edge  218  of the cutting face  206 . In some embodiments, each spoke  220  may traverse only a portion of the planar portion  214 , and therefore, may not reach the periphery and/or the central recess of the cutting face  206 . 
     In some embodiments, each radially extending spoke  220  may comprise an upper surface  222  that may be raised in relation to the substantially planar surfaces  214  of the cutting face  206 . As shown in  FIG. 2A , the upper surface  222  of the spokes  220  may, in some embodiments, be generally planar. In some embodiments, the upper surface  222  of the spoke  220  may be parallel or transverse to the substantially planar portions  214 . 
     As shown in  FIG. 2B , each spoke  220  comprises an interior region  226  and an outer region  228 . The interior region  226  is adjacent the periphery of the recess  216  and the outer region  228  is adjacent the outer circumferential edge of the cutting face  206 . In some aspects, the spoke  220  increases in height from the interior region  226  to the outer region  228 . In some aspects, each spoke  220  may have a maximum height at the outer region  228 . In some aspects, each spoke  220  may have an upper surface  222  that is substantially planar and having a uniform height. As shown in  FIG. 2B , the upper surface  222  of the spoke  220  may have a greater width (laterally relative to the spoke) at the interior region  226  than the outer region  228  of the upper surface  222 . That is, the width of the upper surface  222  decreases from the interior region  226  adjacent the periphery of the central recess  216  to the outer region  228  adjacent the circumferential edge  218  of the cutting face  206 . In some aspects, the width of the upper surface  222  may be uniform and substantially constant from the interior region  226  to the outer region  228 . 
     In some aspects, each spoke  220  comprises side surfaces  224  on opposing sides of the upper lateral spoke surface  222 . The side surfaces  224  of the radially extending spokes  220  may be sloped or angled relative to the substantially planar surfaces  214  of the cutting face  206 . The side surfaces  224  of each spoke  220  may incline toward the substantially planar surfaces  214  of the cutting face  206 . In other words, the side surfaces  224  of the radially extending spoke  220  may extend from the substantially planar surface  214  upward, away from the substantially planar surface  214 , to the upper surface  222  of the spoke  220 . As shown in  FIG. 2B , the side surfaces  224  of the spoke  220  may have a greater width at the outer region  228  than the interior region  226 . That is, the width of the side surfaces  224  increases from the interior region  226  adjacent the periphery of the central recess  216  to the outer region  228  adjacent the edge of the cutting face  206 . In some aspects, the width of the upper surface  222  may be uniform and substantially constant from the interior region  226  to the outer region  228 . 
     As shown in  FIG. 2C , the recess  216  has a depth lower than the maximum height the planar portion  214 . In some aspects, the recess  216  may be located at the longitudinal centerline of the cutting element, e.g., the recess overlaps with the longitudinal centerline of the cutting element. The recess  216  may be circular, oval, cylindrical, polygonal, or irregularly shaped. In some aspects, the recess  216  is substantially circular. In this aspect, the diameter of the recess may vary widely, and may range, for example, from 5-80% of the total cutter diameter, e.g., from 10-75%, from 20 to 70%, from 30 to 65%, from 40 to 60% or from 50 to 60% of the total cutter diameter. 
     It is contemplated that the values of the dimensions of the identified features of the cutting element may, in some embodiments, be larger or smaller than these example values, depending on an intended application of the cutting element. In some embodiments, the planar portion  214  has a transverse cross-sectional shape may be defined by further shapes, e.g., a circular arc. For example, a cross-section of the planar portion  214  may be generally defined as one or more of an elliptical arc, a symmetric curved shape, an asymmetric curved shape, a symmetric V-shape, or an asymmetric V-shape. 
     The diameter of the planar portion  214  may vary widely, and may range, for example, from 5 to 80% of the total cutter diameter, e.g., from 5 to 60%, from 5 to 50%, from 5 to 40%, from 5 to 25% or from 5 to 10% the total cutter diameter. In some aspects, the ratio of the diameter of the recess to the diameter of the planar portion ranges from 0.5:1 to 5:1, e.g., from 0.5:1 to 4:1, from 0.5:1 to 3:1, from 0.5:1 to 2:1, or from 0.5:1 to 1:1. 
     The height of the cutting element (e.g., the substrate and the superabrasive table) may range 1 cm to 10 cm, e.g., from 1.2 cm to 8 cm, from 1.4 cm to 6 cm, from 1.8 cm to 4 cm, or from 2 cm to 3 cm. In some aspects, the height of cutting elements may be a function of the diameter of the cutting element or the diameter of the recess. In some embodiments, the diameter of the cutting element ranges from 0.1 cm to 0.5 cm, e.g., from 0.15 cm to 0.4 cm, from 0.2 cm to 0.355 cm, from 0.203 cm to 0.355 cm, or from 0.225 cm to 0.345 cm. 
     In some embodiments, the height of the cutting element may be quantified as 0.35*cutting element diameter, or up to 0.5*cutting element diameter. In some aspects, the height of the cutting element may be quantified as 1.5*recess diameter, or up to 2*recess diameter. The ratio of the height of the cutting element to the diameter of the cutting element and/or the recess may range from about 0.1:1 to 6:1, e.g., from about 0.5:1 to 3:1 or from 1:1 to 2:1. In some embodiments, the ratio of the diameter of the central recess to the diameter of the cutting element may range from about 0.1:1 to 1:1, e.g., from about 0.2:1 to 0.8:1 or from 0.4:1 to 0.6:1. 
     The contemplated cutting element design may include any number of parameters that can be used to characterize a bit design which include the cutter locations and orientations (e.g., radial and angular positions, heights, profile angles, back rake angles, side rake angles, etc.) and the cutter sizes (e.g., diameter), shapes (i.e., geometry) and bevel size. Additional bit design parameters may include the bit profile, bit diameter, number of blades on bit, blade geometries, blade locations, junk slot areas, bit axial offset (from the axis of rotation), cutter material make-up (e.g., tungsten carbide substrate with hardfacing overlay of selected thickness), etc. 
     In some embodiments, the recess  216  includes a laterally extending convex surface  219 . The convex surface  219  may have a maximum height that is equivalent to a height of the planar portion  214  at a region  215  adjacent to the periphery of the recess  216 . In some aspects, the convex surface  219  may have a maximum height that is greater than or less than the height of the planar portion  214  at a region  215  adjacent to the periphery of the recess  216 . 
     In some embodiments, the cutting element may not include a convex in the recess. For example,  FIG. 3  shows a perspective view of the superabrasive table  304  of a cutting element having a central recess  316  with a planar surface. The superabrasive table  302  may comprise a recess  316  having a planar interior surface  317 . The depth of the recess  316  may be greater than the maximum height of the planar surface  314 . The planar interior surface  317  may be positioned longitudinally below both the radially extending spoke  320  and a portion of the planar portion  314 . In other words, the planar interior surface  317  of the central recess  316  may be positioned within the volume of the superabrasive table  304 . 
     Although the embodiment of  FIG. 3  is shown with a central recess, other embodiments are contemplated that may not include a central recess. For example,  FIG. 4  shows a superabrasive table  400  having a cutting face  402  with a shaped cutter surface according to another embodiment of the present disclosure. In the embodiment shown in  FIG. 4 , the superabrasive table  400  includes a cutting face  402  having a substantially planar central region  404 . A plurality of spokes  406  extend radially outward from the central region  404  to the outer circumferential cutting edge  408  of the cutting face  402 . A plurality of depressions  410  extend between adjacent spokes from a periphery of the central region  404  to the outer circumferential cutting edge  408  of the cutting face  402 . In this embodiment, the cutting face  402  includes a plurality of spokes  406  having an upper surface  412  that is substantially coplanar and continuous with the central region  404  of the cutting face  402 . 
     As shown in  FIG. 4 , the cutting face  402  includes four equidistantly spaced radially extending spokes  406  that extend radially outward from the central region  404  to form a substantially cross-shaped member. Each spoke  406  has an upper surface  412  that is substantially coplanar with the central region  404 . Each spoke  406  may also be continuous with the central region  404 . As used herein, “continuous” refers to a surface that has no breaks or gaps. In the embodiment shown in  FIG. 4 , the entirety of the cross-shaped member may be substantially continuous and planar. That is, each of the radially extending spokes  406  and the central region  404  may be formed on a single plane on the cutting face  402 . In this embodiment, the width of each of the radially extending spokes  406  is substantially constant from the central region  404  to the outer circumferential cutting edge  408 . In some aspects, one or more of the radially extending spokes  406  may have the greatest width adjacent the central region  404  and the smallest width adjacent the outer circumferential cutting edge  408 . 
     Each radially extending spoke  406  may include an interior region adjacent the central region  404 , an outer region adjacent the edge  408  of the cutting face  402 , and an upper surface extending therebetween. In some embodiments, the width of the spoke  406  at the interior region may be larger than the width of the spoke  406  at the outer region. In some cases, the ratio of the width of the spoke at the interior region to the width of the spoke at the outer region ranges from 0.5:1 to 10:1, e.g., from 0.6:1 to 8:1, from 0.8:1 to 7:1, from 0.9:1 to 6:1, from 1:1 to 5:1, or from 2:1 to 4:1. In some cases, each of the radially extending spokes comprises an upper surface having a substantial constant width. In embodiments where the ratio of the width of the spoke at the interior region to the width of the spoke at the outer region is approximately 1:1, the spoke may have a substantially rectangular shape. 
       FIG. 5A  shows a superabrasive table  500  having a cutting face  502  with a shaped cutter surface according to another embodiment of the present disclosure. In the embodiment shown in  FIG. 5A , the superabrasive table  500  includes a cutting face  502  having a substantially planar central region  504 . A plurality of spokes  506  extend radially outward from the central region  504  to the outer circumferential cutting edge  508  of the cutting face  502 . A plurality of depressions  510  extend between adjacent spokes  506  from a periphery of the central region  504  to the outer circumferential cutting edge  508  of the cutting face  502 . In this embodiment, the cutting face  502  includes a plurality of radially extending spokes  506  having an upper surface that is substantially coplanar and continuous with the central region  504  of the cutting face  502 . 
     The superabrasive table  500  may further include a plurality of depressions  510  segmented by the radially extending spokes  506 . Each depression  510  may extend between adjacent spokes  506  from a periphery of the central region  504  to the outer circumferential cutting edge  508  of the cutting face  502 . Each of the depressions  510  may be sloped or angled relative to the central region  504 , the spokes  506 , or both. For example,  FIG. 5A  shows the depressions  510  sloping downward (in the proximal direction relative to the substrate (not shown)), relative to the longitudinal axis of the table  500 , from a region adjacent the central region  504  of the cutting face  502  toward the outer periphery  508  of the cutting face  502 . In this embodiment, the depth of the depression  510  relative to the central region  504  increases from an interior radial region to an outer radial region. In some aspects, the depression  510  may merge with the central region  504  and/or the radially extending spokes  506  at an interior region adjacent the central region  504 . 
       FIG. 5B  shows a top plan view of the superabrasive table of  FIG. 5A . Each spoke  506  may comprise an interior region  514  adjacent the central region  504 , an outer region  516  adjacent the circumferential edge  508  of the cutting face  502 , and an upper surface  512  extending therebetween. In some aspects, the upper surface  512  of each spoke  506  may have a width that is substantially constant from the interior region  514  to the outer region  516 . In other aspects, as shown, the upper surface  512  of each spoke  506  may have a width that decreases from the interior region  514  to the outer region  516 . The upper surfaces  512  of each of radially extending spokes  506  may be continuous with a central region  504  of the cutting element  500 , as shown in  FIGS. 5A and 5B . The upper surface  512  of each radially extending spoke  506  may extend from an outer periphery of the cutting face  502  toward a substantially planar central region  504  of the cutting face  502  in a direction toward the central axis. In some aspects, the radially extending spoke  506  may have a substantially hourglass shape. That is, the upper surface  512  of each spoke  506  has a minimum upper surface width in an intermediate region between the central region  504  and the outer region  516 . 
     In some aspects, each spoke  506  may increase in height from the interior region  514  to the outer region  516 . That is, the spoke  506  may have a maximum height at the outer region  516  adjacent the outer circumferential edge  508  of the cutting face  502 . Conversely, each spoke  506  may decrease in height from the interior region  514  to the outer region  516 . That is, the spoke  506  may have a maximum height at the interior region  514  adjacent the central region  504  of the cutting face  502 . In some embodiments, the upper surface  512  of the spoke  506  may extend from a substantially planar surface near an outer periphery  508  of the superabrasive table  500  radially inward, toward the central axis, away from the substantially planar surface  510 . 
     Each of the spokes  506  may include sidewalls  518  on opposing sides of the upper surface  512 . The sidewalls  518  may extend from the upper surface  512  to the depression  510 . In some aspects, each sidewall  518  may extend from the upper surface  512  to the depression  510  at a transverse angle to the upper surface  512  of the spoke  506 . In the embodiments shown in  FIGS. 5A and 5B , the sidewalls  518  on opposing sides of the upper surface  512  increase in height from the interior region  514  to the outer region  516 . In some embodiments, each sidewall decreases in height from the interior region to the outer region. 
       FIG. 6  illustrates a shaped cutting surface of cutting elements according to some embodiments of the present disclosure. In the embodiment shown in  FIG. 6 , the superabrasive table  600  comprises a cutting element having a shaped cutting face  602 . As previously discussed with respect to  FIG. 5A , the cutting face  602  may include a central region  604  and a plurality of spokes  606  radially extending from the central region  604  to the outer periphery  608  of the cutting face  602 . In this embodiment, the plurality of radially extending spokes  606  having an upper surface  612  that is substantially coplanar and continuous with the central region  604  of the cutting face  602 . For purposes of discussion for  FIG. 6 , the central region  604  and plurality of spokes  606  will be collectively referred to as the “cutting surface.” 
     The cutting surface on the cutting face  602  may generally have a polygonal shape, e.g., cross-shaped polygon, star-shaped polygon, triangular, etc. For example, the cutting surface may include four equidistantly spaced radially extending spokes  606  that extend radially from a central region  604  outwardly to the outer circumference  608  of the cutting face  602 . In embodiment shown in  FIG. 6 , the entirety of the cutting surface has an upper surface  612  that is substantially co-planar and continuous. It is contemplated, however, the cutting surface may include an upper surface  612  that is not coplanar as discussed above. For example, the radially extending spokes  606  may slope downwardly from the central region  604  of the cutting surface outwardly toward the outer circumference  608  of the cutting face  602 , or vice versa. Additionally, the radially extending spokes  606  and/or central region  604  may include grooves or protrusions. 
     Each spoke  606  of the cutting surface includes an interior region  614  adjacent the central region  604  and an outer region  616  adjacent the edge of the cutting face  602 . The upper surface  612  extends between the interior region  614  and the outer region  616 . In the embodiment shown in  FIG. 6 , the upper surface  612  of each spoke  606  has a width that decreases from the interior region  614  to the outer region  616 . In this respect, the each spoke  606  is substantially triangular with various geometric attributes, e.g., width of the spoke, height of the spoke, angles formed by the spoke at the apex, etc. 
       FIG. 7  shows another embodiment of the shaped cutting surface having a cutting surface  704  including a plurality of spokes  706 . In some aspects, the width of the spoke  706  at the interior region  714  may be less than the radius (R 1 ) of the cutting face  702 , e.g., less than R 1 , less than 0.9 R 1 , less than 0.75 R 1 , less than 0.5 R 1 , or less than 0.33 R 1 . In some aspects, the width of the spoke  706  at the outer region  716  may be less than the radius of the cutting face  702 , e.g., less than 0.75 R 1 , less than 0.5 R 1 , less than 0.33 R 1 , or less than 0.25 R 1 . In some aspects, the width of the spoke  706  at the interior region  714  may be substantially equivalent to the width of the spoke  706  at the outer region  716 . In the embodiment shown in  FIG. 7 , the width of the spoke  706  at the interior region  714  is substantially larger than that shown in  FIG. 6 . In this respect, the cutting surface  704  of  FIG. 7  has a much larger surface area, e.g., contact surface, than the cutting surface of  FIG. 6 . In some embodiments, the plurality of spokes comprises greater than 25% of the total surface area of the cutting face, e.g., greater than 30%, greater than 40%, greater than 50%, or greater than 60%. In some cases, the cutting surface (e.g., the plurality of spokes taken together with the central region), comprises greater than 40% of the total surface area of the cutting face, e.g., greater than 50%, greater than 60%, greater than 70%, or greater than 80%. 
     The superabrasive table  700  may further include one or more regions  710  separated by the cutting surface  704 . Each region  710  may extend between adjacent spokes  706  from a periphery of the central region  708  of the cutting surface  704  to the outer circumferential edge of the cutting face  702 . Each of the regions  710  may be sloped or angled relative to the cutting surface  704  of the cutting face  702 . As shown in  FIG. 7 , each of the regions  710  slope downwardly from an interior radial region  714  adjacent the central region  708  of the cutting surface  704  towards an outer radial region  716  of the cutting face  702 . In these embodiments, the depth of each of the regions  710  increases from an interior radial region  714  to an outer radial region  716 . In some aspects, a portion of the region  710  adjacent the central region  708 , e.g., proximate to the interior radial region  714 , merges with a portion of the cutting surface  704 . For example, portion of the region  710  adjacent the central region  708  may merge with a portion of the spoke  706  and/or the central region  708  of the cutting surface  704 . 
     As shown in  FIG. 8 , the upper surface  812  of the radially extending spoke  806  may not extend completely across the cutting face  802  to the circumferential edge of the cutting face  802 . That is, the radially extending spoke  806  may positioned radially inward from a substantially planar portion of the cutting face  802  adjacent a cutting edge of the cutting face  802 . For example,  FIG. 8  shows a radially extending spoke  806  extending from an interior region  814  adjacent the central region  808  to an exterior region  816  adjacent the cutting edge of the cutting face  802 . The substantially planar portion may separate the termination point of the spoke  806  and the circumferential edge of the cutting face  802 , e.g., interface of the cutting face and the chamfer. In this embodiment, the upper surface  812  of the cutting surface  804  is substantially continuous and coplanar. The cutting surface  804  may include a star-shaped member, optionally having three, four, five, six or more points, disposed on the cutting face  802 . In some aspects, the cutting surface  804  may be integrally formed on the cutting face  802  and the entirety of the cutting surface  804  is raised in relation to a substantially planar cutting face  802 . In this embodiment, the regions  810  may be planar and flat. 
     In some aspects, the upper surface  812  of at least one spoke  806  is angled relative to a substantially planar surface of cutting surface  804  of the superabrasive table. Each radially extending spoke  806  may have a substantially uniform circumferential width along a radially extending length. However, in additional embodiments, the circumferential width of a radially extending spoke  806  may vary along a radially extending length. 
     As shown in  FIG. 9 , the superabrasive table  900  may comprise a cutting face  902  having three radially extending spokes  904 . The three radially extending spokes  904  segment the cutting face  902  into three distinct regions  906  separated by each of the spokes  904 . The radially extending spokes  904  may be equidistantly spaced on the cutting face. For example, the radial distance between each of the radially extending spokes  904  may be equivalent from any distance along the diameter of the cutting face  902 . In this respect, each segmented region  906  separated by the radially extending spokes  904  may have substantially the same surface area and/or radius. In some embodiments, the radially extending spokes  904  may be unevenly spaced between each of the radially extending spokes  904 , e.g., Y-shaped, T-shaped, or variations thereof. 
     Each of the segmented regions  906  may extend between adjacent spokes  904  from a periphery of the central region  910  of the cutting face  902  to the outer periphery  914  of the cutting face  902 . The segmented regions  906  may be sloped or angled relative to the upper surface of the radially extending spokes  904 . As shown in  FIG. 9 , the segmented regions  906  may decline from a region  912  adjacent the central region  910  of the cutting face towards the outer periphery  914  of the cutting face. For example, the segmented regions  906  may have the greatest height at the region  912  adjacent the central region  910 . Conversely, the segmented regions  906  may have the greatest height at the region adjacent the outer periphery  914  of the cutting face  902 . In some aspects, the depth of the segmented regions  906  may be substantially constant from the region  912  adjacent the central region  910  to the outer periphery  914  of the cutting face  902 . 
     In some embodiments, a cutter element employing the superabrasive table  900  shown in  FIG. 9  may be useful as a low profile cutter. That is, the cutter element may be mounted on the rotary drill bit to have a relatively low exposure height, e.g., a low profile cutter. For example, in a fixed cutter drill bit having radially-spaced sets of cutter elements, the cutter element sets preferably overlap in rotated profile and include at least one low profile cutter element. The low profile element is mounted to have a relatively low exposure height. Providing an arrangement of low and, for example, high profile cutter elements, tends to increase the bit&#39;s ability to resist vibration and provides an aggressive cutting structure, even after significant wear has occurred. 
       FIG. 10  shows another embodiment of the shaped cutter element having one or more depressed regions. The superabrasive table  1000  of the cutting element may comprise a cutting face  1002  having one or more radially extending spokes  1004  that segment the cutting face  1002  into one or more regions defined in the cutting face  1002 . In the embodiment shown in  FIG. 10 , a plurality of depressed regions  1006  are positioned proximate to a peripheral edge  1008  of the cutting face  1002 , e.g., proximate to the chamfer. For example, a generally triangular depressed region  1006  may be defined in the cutting face  1002  of the superabrasive table  1000 , which may be divided into segments by the radially extending spokes  1004 . In some embodiments, an interior region of each depression, adjacent the central region, forms an obtuse angle between adjacent spokes. In some embodiments, an interior region of each depression between adjacent spokes forms an angle ranging from 90° to 180°, e.g., from 95° to 170°, from 100° to 160°, or from 120° to 140°. 
     As shown in  FIG. 10 , the entirety of the one or more regions  1006  is positioned radially inward from a substantially planar portion  1014  of the cutting face  1002  adjacent a peripheral edge  1008  of the cutting face  1002  with respect to a longitudinal axis of superabrasive table  1000 . That is, one or more depressed regions  1006  formed on the cutting face  1002  may extend radially from proximate the substantially planar peripheral edge portion  1014  to a central region  1012  of the cutting face  1002 . In this embodiment, at least a portion of the region  1006  does not extend to the peripheral edge  1008  of the cutting face  1002 . In other words, a portion of region  1006  is separated by the substantially planar portion  1014  from the peripheral edge  1008  of the cutting face  1002 . 
       FIG. 11  shows another embodiment of the shaped cutter element having one or more depressed regions. In this embodiment, one or more depressed regions  1106  extend radially outward from a region adjacent the central region  1112  of the cutting face  1102  proximate a longitudinal central axis to the peripheral edge  1108  of the cutting face  1102 . That is, the cutting face shown  FIG. 11  does not include a substantially planar portion adjacent the peripheral edge  1108  of the cutting face  1102 . The depressed regions  1106  defined in the cutting face  1102  may be positioned proximate to or at the peripheral edge  1108  of the cutting face  1102 , such as proximate to the chamfer surface, and may extend generally radially from the peripheral edge  1108  to a region proximate to the central region  1112 . 
     The depressed regions  1106  may extend between adjacent spokes  1104  from a region adjacent the central region  1112  of the cutting face  1102  to the peripheral edge  1108  of the cutting face  1102 . The depressed regions  1106  may be sloped or angled relative to the upper surface of the radially extending spokes  1104 . For example, the depressed regions  1106  may slope upwardly (or downwardly) away from the longitudinal centerline of the cutting face  1102  from a region adjacent the central region  1112  of the cutting face towards the peripheral edge  1108  of the cutting face  1102 . In some embodiments, each depression has a depth that decreases from an interior radial region (e.g., adjacent the central region) to an outer radial region (e.g., adjacent the cutting edge). In some embodiments, each depression has a depth that increases from an interior radial region (e.g., adjacent the central region) to an outer radial region (e.g., adjacent the cutting edge). 
     In some embodiments, the depressed region  1106  may have the greatest depth at a region adjacent the central region  1112 . In some aspects, the depressed region  1106  may merge with the cutting face  1102  at a region adjacent the peripheral edge  1108  of the cutting face  1102  as shown in  FIG. 11 . In particular, the depressed region  1106  may be coplanar with the cutting face  1102  at a region adjacent the peripheral edge  1108  of the cutting face  1102 . In some cases, each of the spokes  1104  may have an hourglass-like shape. That is, each of the spokes  1104  may comprise an upper surface with an intermediate region between the central region  1112  and the peripheral edge  1108  that has a minimum width. In some aspects, each depression merges with a portion of one or more spokes at the interior region adjacent the central region. 
     Each of the depressed regions  1106  defined in the cutting face  1102  may be defined by an arcuate cross-section having a primary surface with a cross-sectional dimension defined by a radius. For example, each region  1106  may be an arcuate depression defined by a radius R 1 . Of course, values of the dimensions of the identified features of the cutting element may, in some embodiments, be larger or smaller than these example values, depending on an intended application of the cutting element, for example. 
     As shown in  FIG. 11 , each spoke  1104  may traverse at least a portion of the depressed region  1106  and, therefore, may extend at least partially between a central region  1112  of the superabrasive table  1100  (i.e., a region at or proximate the central axis) and a peripheral edge  1108  of the superabrasive table  1100 . For example, each spoke  1104  may traverse the entire depression  1106  and extend from the central region  1112  to the peripheral edge  1108  of the table  1100 . In some embodiments, as shown in  FIG. 11 , each radially extending spoke may comprise an upper surface that may be coplanar with the central region  1112  of the cutting face  1102 . The side surfaces of the spokes  1104  proximate the region  1106  may, in some embodiments, be generally planar and perpendicular to the upper surfaces of the spokes  1104 . 
     As shown in the embodiments of  FIGS. 12-16 , the cutting element may have shaped cutters with asymmetric cutting surfaces according to some embodiments of the present disclosure. Each of the embodiments shown in  FIGS. 12-16  provide asymmetric configurations of the cutting surface on the cutting face. In other words, the cutting surface has no axis of mirror symmetry and so defines a cutting surface having a cutting profile of an asymmetric shape. The asymmetric cutting shape may increase the depth of rock formation cut by each cutting element. In some embodiments, the superabrasive table may, for example, exhibit a non-planar, asymmetric cutting face that requires a particular orientation relative to a rotational path traveled by the cutting element in order to effectively engage the subterranean formation. In general, each of the cutting elements shown in  FIGS. 12-16  includes a cutting face having one or more radially extending spokes that may segment the cutting face into one or more regions defined in the cutting face. 
       FIG. 12  shows one embodiment of the shaped cutting element  1200  with an asymmetric cutting surface. The cutting face  1202  may comprise a plurality of radially extending spokes  1204 A-D. In some aspects, each pair of opposing spokes ( 1204 A,B and  1204 C,D) are offset on the cutting face  1202 . In particular, at least two opposing spokes  1204 A,  1204 B are offset with respect to the y-axis of the cutting face  1202  and at least two opposing spokes  1204 C,  1204 D are offset with respect to the x-axis of the cutting face  1202 . In this embodiment, the segmented regions  1206  may have different surface areas. For example, the segmented regions  1206  on opposing sides of the cutting face  1202  may have the same or substantially the same surface area and adjacent segmented regions  1206  may have different surface areas. 
     Each of the radially extending spokes  1204 A-D may have a leading wall  1208  and a trailing wall  1210 . As shown in  FIG. 12 , the leading wall  1208  may have a shorter length than the trailing wall  1210 . For example, when taken in the clockwise direction, the leading wall  1208  has a shorter length than the trailing wall  1210 . In some cases, the leading wall  1208  may have a longer length than the trailing wall  1210 . For example, when taken in the clockwise direction, the leading wall  1208  has a longer length than the trailing wall  1210 . Each of the radially extending spokes  1204 A-D may be substantially coplanar and continuous with a central region of the cutting face  1202 . 
       FIG. 13  shows another embodiment of the shaped cutting element  1300  having an asymmetric cutting face  1302 . In this embodiment, each pair of adjacent spokes  1304  may form an angle on the cutting face  1302 . The spokes  1304  may be angled with respect to an opposing spoke, or each spoke may have different angles on the cutting face with respect to the longitudinal axis of the cutting face  1302 . In particular, opposing spokes  1304  may be at different angles with respect to the longitudinal axis of the cutting face  1302  to provide an asymmetric cutting surface. For example, each pair of adjacent spokes  1304  can form an angle on the cutting face that is different from an angle formed by another pair of adjacent spokes  1304 . In some embodiments, the angle formed between each pair of adjacent spokes  1304  is the same, e.g., all four angles on the cutting face may be equivalent. In some embodiments, each pair of adjacent spokes  1304  forms an angle on the cutting face that is different and distinct than angle formed by another pair of adjacent spokes  1304 . In this embodiment, the segmented regions  1306  may have different surface areas. 
       FIGS. 14 and 15  show some embodiments of the shaped cutting element having an asymmetric cutting face. In each of  FIGS. 14 and 15 , the cutting face comprises at least four spokes extending from a central region of the cutting face, e.g., at or proximate to the longitudinal center of the cutting element, to an outer periphery of the cutting face. Each of the at least four spokes have opposing lateral sides that are not mirror images of each other, e.g., asymmetric. For example, at least one of the lateral sides of the spoke is convex and/or at least one of the lateral sides is concave. 
     In  FIG. 14 , each of the spokes  1404  comprise a leading wall  1408  and a trailing wall  1410 . In this embodiment, the leading wall  1408  comprise a convex portion and the trailing wall  1410  comprises a concave portion. In the embodiment shown in  FIG. 15 , the leading wall  1508  comprises a concave portion and the trailing wall  1510  comprise a convex portion. In these embodiments, the intersection point of each pair of adjacent spokes  1502  are generally rounded, e.g., curved. 
       FIG. 16  shows another embodiment of the shaped cutting element having an asymmetric cutting face  1602 . The cutting face  1602  may comprise a plurality of spokes  1604  that are separated by depressed regions  1606 . Each of the plurality of spokes  1604  may comprise a leading wall  1608  and a trailing wall  1610 . In this embodiment, the leading wall  1608  and the trailing wall  1610  may be substantially linear. In some aspects, the trailing wall  1610  is convex and the leading wall  1608  is linear. For example, the cutting face  1602  may comprise a trailing wall  1608  that is a concave or convex, and a leading wall  1610  that is substantially linear, or vice versa. The substantially straight edge may form a sharp intersection between each pair of adjacent spokes  1604 . 
     In the embodiments shown in  FIGS. 12-16 , the spokes are generally raised in relation to the cutting face of the superabrasive table. The spokes include an upper surface that is substantially coplanar and continuous with the central region. In some embodiments, each of the spokes may include a first side extending from the upper surface of the spoke to the cutting face and an opposing second side extending from the upper surface to the cutting face. As explained above, the first side and the second side of the spoke may be concave, convex, or substantially linear. For example, one or more spokes may include a first side surface that is convex and the second side surface of the spoke may be concave. 
     The cutting face may exhibit any desired peripheral geometric configuration (e.g., peripheral shape and peripheral size). The peripheral geometric configuration of the cutting face may be selected relative to a desired position of the cutting element on an earth-boring tool to provide the cutting face with desired interaction (e.g., engagement) with a subterranean formation during use and operation of the earth-boring tool. For example, the shape of the cutting face may be selected to facilitate one or more of shearing, crushing, and gouging of the subterranean formation during use and operation of the earth-boring tool. 
     The cutting face may exhibit a substantially consistent lateral cross-sectional shape but variable lateral cross-sectional dimensions throughout a longitudinal thickness thereof, may exhibit a different substantially consistent lateral cross-sectional shape and substantially consistent lateral cross-sectional dimensions throughout the longitudinal thickness thereof, or may exhibit a variable lateral cross-sectional shape and variable lateral cross-sectional dimensions throughout the longitudinal thickness thereof. By way of non-limiting example, the cutting face may exhibit a chisel shape, a frustoconical shape, a conical shape, a dome shape, an elliptical cylinder shape, a rectangular cylinder shape, a circular cylinder shape, a pyramidal shape, a frusto pyramidal shape, a fin shape, a pillar shape, a stud shape, a truncated version of one of the foregoing shapes, or a combination of two or more of the foregoing shapes. 
     Accordingly, the cutting face may have any desired lateral cross-sectional shape including, but not limited to, an elliptical shape, a circular shape, a tetragonal shape (e.g., square, rectangular, trapezium, trapezoidal, parallelogram, etc.), a triangular shape, a semicircular shape, an ovular shape, a semicircular shape, a tombstone shape, a tear drop shape, a crescent shape, or a combination of two or more of the foregoing shapes. The peripheral shape of cutting face may be symmetric, or may be asymmetric. 
     EXAMPLE 
     Subterranean drilling runs were performed in Dewey County, Okla. using 6.125 inch bits. Most runs were performed using flat table PDC cutters on standard rotary bits, but a select few were performed using the cutters of  FIGS. 5A and 5B . The cutters were run on rotary drill bits having 6 or 7 blades. The rotary drill bits were tested on granite formations between 20,000 and 25,000 psi. 
     The top ten longest runs were selected and compared to one another. The results are provided in  FIG. 17 . As shown, two of the top five runs, including the longest run, employed the shaped cutters described herein. In fact, the best run was 9303 feet, which bested the second best run of 5847 feet by 3456 feet, which is an increase of 59% in footage drilled. 
     Embodiments 
     Embodiment 1: A cutting element, comprising: a substantially cylindrical substrate; a superabrasive table positioned on the cylindrical substrate, the superabrasive table comprising: a cutting face having a substantially planar portion surrounding a central recess, the planar portion extending laterally to an outer circumferential edge; and at least one spoke disposed on the cutting face, the spoke extending radially from a periphery of the recess to the outer circumferential edge. 
     Embodiment 2: An embodiment of embodiment 1, wherein each spoke comprises an upper surface having an interior region adjacent the periphery of the recess and an outer region adjacent the edge of the cutting face, wherein the upper surface has an upper surface width that decreases from the interior region to the outer region. 
     Embodiment 3: An embodiment of embodiment 1, wherein the spoke is raised in relation to the planar portion of the cutting face. 
     Embodiment 4: An embodiment of embodiment 1, wherein the spoke comprises an interior region adjacent the periphery of the recess and an outer region adjacent the edge of the cutting face, wherein the spoke has a height that increases from the interior region to the outer region, and wherein the spoke has a maximum height at the outer region. 
     Embodiment 5: An embodiment of embodiment 1, wherein the spoke comprises an interior region adjacent the periphery of the recess, an outer region adjacent the edge of the cutting face, and an upper lateral spoke surface extending therebetween, wherein the spoke comprises sidewalls on opposing sides of the upper lateral spoke surface, each of the sidewalls extending from the upper lateral spoke surface to the planar portion of the cutting face. 
     Embodiment 6: An embodiment of embodiment 1, wherein each of the sidewalls are transverse relative to the upper lateral spoke surface of the spoke and the planar portion of the cutting face, wherein each sidewall increases in height from the interior region to the outer region. 
     Embodiment 7: An embodiment of embodiment 1, comprising at least four spokes equidistantly spaced on the cutting face, wherein the planar portion is divided into four separate planar portions, each pair of adjacent spokes being separated by a respective planar portion. 
     Embodiment 8: An embodiment of embodiment 1, wherein the recess is substantially circular and is defined by a laterally extending convex surface and a longitudinally extending circumferential side wall. 
     Embodiment 9: An embodiment of embodiment 1, wherein the superabrasive table comprises a chamfered region between the edge of the cutting face and a sidewall of the cylindrical substrate. 
     Embodiment 10: A cutting element for drilling subterranean formations, comprising: a substantially cylindrical substrate; a superabrasive table positioned on the cylindrical substrate, the superabrasive table comprising: a cutting face having a substantially planar central region and an outer circumferential cutting edge; a plurality of spokes extending radially outward from the central region to the edge of the cutting face, wherein each spoke comprises an interior region adjacent the central region, an outer region adjacent the edge of the cutting face, and an upper surface extending therebetween, wherein a ratio of an upper surface width at the interior region to the upper surface width at the outer region ranges from 0.5:1 to 2:1; and a plurality of depressions, each depression extending between adjacent spokes and from a periphery of the central region to the outer circumferential cutting edge of the cutting face. 
     Embodiment 11: An embodiment of embodiment 10, wherein the upper surface of each spoke is substantially co-planar and continuous with the central region. 
     Embodiment 12: An embodiment of embodiment 10, wherein the upper surface of each spoke has a width that is substantially constant from the interior region to the outer region. 
     Embodiment 13: An embodiment of embodiment 10, wherein the upper surface of each spoke has a width that decreases from the interior region to the outer region. 
     Embodiment 14: An embodiment of embodiment 10, wherein each depression has a depth that increases from an interior radial region to an outer radial region, wherein each depression merges with the cutting edge. 
     Embodiment 15: An embodiment of embodiment 10, wherein each depression merges with a portion of one or more spokes at the interior region adjacent the central region. 
     Embodiment 16: An embodiment of embodiment 10, wherein the cutting face does not include a substantially planar outer lateral circumferential portion adjacent the cutting edge of the cutting face. 
     Embodiment 17: An embodiment of embodiment 10, wherein each spoke increases in height from the interior region to the outer region, and wherein the spoke has a maximum height at the outer region. 
     Embodiment 18: An embodiment of embodiment 10, wherein each spoke includes sidewalls on opposing sides of the upper surface, each of the sidewalls extending from the upper surface to the depression. 
     Embodiment 19: An embodiment of embodiment 18, wherein each sidewall extends from the upper surface to the depression of an associated spoke at a transverse angle. 
     Embodiment 20: An embodiment of embodiment 10, comprising at least four spokes equidistantly spaced on the cutting face, wherein each of the at least four spokes are symmetrically arranged on the cutting face, wherein each of the at least four spokes are continuous and co-planar with the central region. 
     Embodiment 21: An embodiment of embodiment 10, wherein the upper surface has a minimum upper surface width in an intermediate region between the central region and the outer region. 
     Embodiment 22: An embodiment of embodiment 10, wherein an interior region of each depression forms an angle ranging from 45° to 180° between adjacent spokes. 
     Embodiment 23: An embodiment of embodiment 10, wherein each depression has a depth that is constant or decreases from an interior radial region to an outer radial region. 
     Embodiment 24: An embodiment of embodiment 23, wherein the cutting face includes a substantially planar outer lateral circumferential portion adjacent the cutting edge of the cutting face. 
     Embodiment 25: An embodiment of embodiment 23, wherein each spoke comprises an interior region adjacent the central region, an outer region adjacent the edge of the cutting face, and an upper surface extending therebetween, wherein the upper surface has a minimum upper surface width in an intermediate region between the central region and the outer region. 
     Embodiment 26: A cutting element for drilling subterranean formations, comprising: a substantially cylindrical substrate; a superabrasive table positioned on the cylindrical substrate, the superabrasive table comprising: an asymmetric cutting face having a substantially planar central region and an outer circumferential cutting edge; a plurality of spokes extending radially outward from the central region to the edge of the cutting face, each spoke comprises an interior region adjacent the central region, an outer region adjacent the cutting edge of the cutting face, and an upper surface extending therebetween, wherein each spoke includes sidewalls on opposing sides of the upper surface; and a plurality of depressions, each depression extending between adjacent spokes and from a periphery of the central region to the outer circumferential cutting edge of the cutting face. 
     Embodiment 27: An embodiment of embodiment 26, wherein each spoke has a leading sidewall and a trailing sidewall and, when taken in the clockwise direction, the leading sidewall has a shorter length than the trailing sidewall. 
     Embodiment 28: An embodiment of embodiment 26, wherein each spoke has a leading sidewall and a trailing sidewall and, when taken in the clockwise direction, the leading sidewall has a longer length than the trailing sidewall. 
     Embodiment 29: An embodiment of embodiment 26, wherein the sidewalls of each of the spokes are not mirror images of each other. 
     Embodiment 30: An embodiment of embodiment 26, wherein at least one of the sidewalls is convex. 
     Embodiment 31: An embodiment of embodiment 26, wherein at least one of the sidewalls is concave. 
     Embodiment 32: An embodiment of embodiment 26, wherein the upper surface of each spoke is substantially co-planar continuous with the central region. 
     Embodiment 33: An embodiment of embodiment 26, comprising at least four spokes spaced apart on the cutting face, wherein each of the at least four spokes are continuous and co-planar with the central region. 
     It should be understood that various different features described herein may be used interchangeably with various embodiments. For example, if one feature is described with respect to particular example, it is understood that that same feature may be used with other examples as well. 
     Although certain embodiments have been shown and described, it should be understood that changes and modifications, additions and deletions may be made to the structures and methods recited above and shown in the drawings without departing from the scope or spirit of the disclosure or the following claims.