Patent Publication Number: US-11655681-B2

Title: Inner cutter for drilling

Description:
PRIORITY CLAIM 
     This application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 62/776,021, filed Dec. 6, 2018, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The disclosure generally relates to the field of drilling components, and more particularly to drill bit components. 
     Wellbores are frequently formed in geological formations using rotary drill bits. Various types of rotary drill bits are known in the art, whereby the wellbore is drilled by powered rotation of the drill bit against a formation under an axial load. A fixed cutter drill bit, for example, includes a circumferentially spaced structures known as blades. A plurality of cutters mounted at different fixed positions on the blades are responsible for cutting through the rock by mechanically destroying and removing rock in the drill bit path. The cutter(s) with the shortest radius from the drill bit&#39;s axis of rotation is/are commonly referred to as the innermost or center cutters. Each of the cutters can include a substrate, such as carbide, and a superhard, wear-resistant cutting material, such as a polycrystalline diamond compact (PDC) material mounted on the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the disclosure can be better understood by referencing the accompanying drawings. 
         FIG.  1 A  is an elevation view of a drilling system with a drill bit with cutters. 
         FIG.  1 B  is a diagram illustrating a drill bit in accordance with various embodiments of the disclosure. 
         FIG.  2    is an isometric view of a fixed-cutter drill bit with cutters. 
         FIG.  3    includes a set of profiles corresponding to the cutters and blades on a drill bit. 
         FIG.  4 A  depicts a first view of an embodiment of a first innermost cutter. 
         FIG.  4 B  depicts a second view of the embodiment of the first innermost cutter. 
         FIG.  5    depicts a view of another embodiment of a first innermost cutter. 
         FIGS.  6 - 7    depict views of a second innermost cutter. 
         FIG.  8    includes views of a third innermost cutter and a fourth innermost cutter. 
         FIG.  9    is a view of a fifth cutter. 
         FIG.  10    is a top view of a first example bottom hole pattern formed as a result of the drilling with a drill bit having an innermost cutter. 
         FIG.  11    is a top view of second example bottom hole pattern formed as a result of the drilling with a drill bit having an innermost cutter. 
         FIG.  12    is an isometric view of a third example bottom hole pattern formed as a result of the drilling with a drill bit having an innermost cutter. 
         FIG.  13    is a flowchart of a method according to one or more embodiments to the disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The description that follows includes example systems, methods, techniques, and program flows that describe various embodiments of the disclosure. However, it is understood that these embodiments can be practiced without these specific details. For instance, this disclosure refers to cutters having one, two, or three reliefs in illustrative examples. Embodiments of this disclosure can be also applied to cutters having any other number of reliefs. In other instances, well-known instruction instances, protocols, structures and techniques have not been shown in detail in order not to obfuscate the description. 
     Embodiments of drill bits as described in this disclosure include drill bits configured to perform drilling operations in geological formations to create a borehole, for example in an oil or gas well environment. Embodiments of the drill bits are configured to generate and allow the recovery of micro cores as part of the drilling operation. A micro core may comprise a solid piece of the foundation material thru which any of the embodiments of a drill bit as described herein may be operating to drill through. A micro core may be a generally cylindrical shaped piece of the foundation material having a diameter in cross-section that is less than a diameter in cross-section of the borehole being created by the drill bit. In various examples, a micro core includes a piece of foundation material having a diameter in a range of 10 to 40 millimeters (mm) in cross-section. In various embodiments, a micro core has a length dimension along a longitudinal axis of the cylindrical shaped micro core that is at least two time the diameter in cross-section of the same micro core. As further described below, embodiments of the drill bit configured to generate micro cores as part of the drilling process include a recessed center area at the bottom portion or area of the drill bit, the bottom portion or area of the drill bit configured to contact and drill away the terminus portion of a borehole being formed by the drill bit. The recessed center area is at least partially enclosed by the one or more innermost cutters of the drill bit, wherein the inner most cutters is configured to generate a micro core within the recessed center area as the drill bit proceeds into the formation material being drilled by the drilling process. The one or more inner most cutters may further be configured to fracture the micro core from the remainder of the foundation material once the micro core is formed as part of the drilling operation. Embodiments of the drill bit may further include an escapeway that allows the micro cores, once fractured from the foundation material, to be conveyed toward the top surface of the borehole being formed by the drilling operation, for example in a flow of drilling fluid being circulated to and/or thru the drill bit. 
     In various embodiments of the drill bits described herein, the innermost cutter can include a relief on the cutting material of the cutting surface, wherein at least one end of the relief is located at and interrupts a cutting arc. The relief can be formed in various indented shapes, such as a linear indentation, a curved groove, etc. The relief can include various specific shapes. For example, the relief can include a first curved edge, followed by a straight edge, followed by a second curved edge, wherein a curved edge can be any edge wherein two sides of the cutting surface material are at an angle less than zero. In some embodiments, the first curved edge and the second curved edge can cooperate to increase the edge toughness of the cutting surface. In some embodiments, drilling using a straight edge of the relief results in the generation of a micro core using the drill bit. The second curved edge can operate to fracture the micro core under the side load of the drill bit. Additionally, in some embodiments, the cutting arc of engagement between an innermost cutter of the drill bit and a formation can be longer than any other cutters on the drill bit. 
     By using one or more of the innermost cutters described in this disclosure, a drill bit can be used to generate a series of micro cores as the drilling progresses. Forming these micro cores as part of the drilling process may increase the overall efficiency of the drilling process due in part to an increased susceptibility of the micro core to be fractured from the foundation material being drilled and/or conveyed away from the terminus of the borehole in one larger size piece of material. In addition, the larger single piece of foundation material included as part of the micro cores being generated by the drilling process may allow for easier capture and testing of the materials being generated at any particular stage of the drilling process. By generating a rock sample that is easier to remove from the borehole and to perform testing on, the embodiments of the drill bits as described in this disclosure may increase the efficiency and effectiveness of a coring procedure during drilling. 
       FIG.  1 A  is an elevation view of a drilling system with a drill bit with cutters. A drilling system  100  is configured to drill into one or more geological formations to form a wellbore  107   a ,  107   b , sometimes also referred to as a borehole. The drilling system  100  can include a drill bit  101  and a well site  106 . Drill bit  101  may comprise any embodiments of the drill bits described in this disclosure, or any equivalents thereof, including drill bits configured with one or more innermost cutters as described in this disclosure, or any equivalents thereof, which may be configured to generate micro cores as part of a drilling operation. Various types of drilling equipment such as a rotary table, mud pumps and mud tanks (not expressly shown) can be located at the well surface or well site  106 . The well site  106  can include a drilling rig  102  that can have various characteristics and features associated with a “land drilling rig”. However, other drill bits can be satisfactorily used with drilling equipment located on offshore platforms, drill ships, semi-submersibles and drilling barges. 
     The drilling system  100  can include a drill string  103  associated with the drill bit  101  that can be used to rotate the drill bit  101  in a radial direction  105  around a bit rotational axis  104  of form a wide variety of wellbores  107   a ,  107   b ; such as a generally vertical wellbore  107   a  or a generally horizontal wellbore  107   b  as shown in  FIG.  1 A . Various directional drilling techniques and associated components of a bottom hole assembly (BHA)  120  of the drill string  103  can be used to form the generally horizontal wellbore  107   b . For example, lateral forces can be applied to the drill bit  101  proximate a kickoff location  113  to form the generally horizontal wellbore  107   b  extending from the generally vertical wellbore  107   a . Each of the wellbores  107   a ,  107   b  can be drilled to a drilling distance, which is the distance between the well surface and the furthest extent of each of the wellbores  107   a ,  107   b , respectively. 
     The BHA  120  can be formed from a wide variety of components configured to form the wellbores  107   a ,  107   b . For example, the components  121   a ,  121   b  and  121   c  of BHA  120  can include, but are not limited to the drill bit  101 , drill collars, rotary steering tools, directional drilling tools, downhole drilling motors, reamers, hole enlargers or stabilizers. The number of components such as drill collars and different types of components  121   a ,  121   b ,  121   c  included in the BHA  120  can depend upon anticipated downhole drilling conditions and the type of wellbore that will be formed by the drill string  103  and the drill bit  101 . The wellbore  107   a  can be defined in part by a casing string  110  that can extend from the well site  106  to a selected downhole location. Various types of drilling fluid can be pumped from the well site  106  through the drill string  103  to the drill bit  101 . The components  121   a ,  121   b , and  121   c  can be attached to the drill bit  101  at an uphole end  158  of the drill bit  101 . 
     Drilling fluids can be directed to flow from the drill string  103  to respective nozzles included in the drill bit  101 . The drilling fluid can be circulated back to the well site  106  through an annulus  108  defined in part by an outside diameter  112  of the drill string  103  and an inside diameter  111  of the casing string  110 . The drill bit  101  can include a plurality of blades  152   a - 152   g . Each of the plurality of blades  152   a - 152   g  can be disposed outwardly from the exterior of a bit body  151  of the drill bit  101 . Each of the plurality of blades  152   a - 152   g  can include a set of cutters  153  that can drill away material surrounding the drill bit  101  in a downhole direction  159 . The bit body  151  can be generally cylindrical and the blades  152   a - 152   g  may comprise any suitable type of projections extending outwardly (i.e. in a radial direction from the bit rotational axis  104 ) from the bit body  151 . The arrangements of the blades and/or the circulation of the drilling fluids may be utilized in various embodiments to urge fractured micro cores away from a bottom area and/or the recessed central area of the drill bit as further described below, for example to enable more efficient drilling and/or allow for capture and inspection/testing/and other analysis of the captured micro cores being generated as part of a drilling operation. 
       FIG.  1 B  is a diagram  160  illustrating a drill bit  161  in accordance with various embodiments of the disclosure. Drill bit  161  may be an embodiment of drill bit  101  that may be included as part of drilling system  100  as illustrated and described with respect to  FIG.  1 A . Referring back to  FIG.  1 B , drill bit  161  may include any of the features, such as cutters and reliefs, arranged to perform any of the functions and/or to provide any of the features of the drill bits and cutters as illustrated and described throughout this disclosure, and any equivalents thereof. 
     As illustrated in  FIG.  1 B , diagram  160  includes drill bit  161  coupled to a drill collar  162  that may include a plurality of drill pipes forming a drill string and extending into a borehole, the borehole generally indicated as the borehole below a bracket indicated by reference number  165 , (hereinafter “borehole  165 ”). Borehole  165  includes borehole walls  164  that extend from surface  163  to a terminus  167  of the borehole. As shown in  FIG.  1 B , the terminus  167  of borehole  165  has a shape that generally conforms to contours of a distal or “bottom” portion  177  of drill bit  161 . Embodiments of drill bit  161  may include one or more blades, illustrated in  FIG.  1 B  as blades  172 A and  172 B. Each of blades  172 A and  172 B includes a plurality of cutters (not shown in  FIG.  1 B  for clarity sake, but for example cutters  203 ,  FIG.  2   ). Each of blades  172 A,  172 B includes a respective inner most cutter  173 A,  173 B. Inner most cutters  173 A and  173 B are positioned adjacent to sidewalls  171  of a recessed central opening in the bottom portion of drill bit  161 , the sidewalls extending from a bottom portion  177  of the drill bit to a central drill bit surface  170  that is recessed away from the bottom portion of the drill bit. As shown in  FIG.  1 B , the sidewalls  171  are spaced around the recessed central opening in the bottom portion  177  of the drill bit  161  so that as the drill bit is operated to extend the borehole  165  further into formation  169 , a micro core  175  is formed from a portion of the formation cut away on the sides by the innermost cutters  173 A and  173 B. Micro core  175  extends into the recessed central opening and toward central drill bit surface  170  of drill bit  161 . In some embodiments, the shape of micro core  175  is generally an upright cylinder, although embodiments of micro core  175  are not necessarily limited to having an upright cylindrical shape. As further described below, inner most cutters  173 A,  173 B include at least one relief, illustrated in  FIG.  1 B  as reliefs  174 A,  174 B, respectively. The reliefs having a particular shape, such as but not limited to a non-circular or a non-elliptical shape, that is configured to produce a side force on micro core  175  as part of the drilling operation. This side force may contribute to producing a fracture  176  that separates micro core  175  from the remainder of formation  169 . In various embodiments, the drilling process utilizing drill bit  161  may progress downward within borehole  165  to the extent that the micro core  175  comes into direct contact with the central drill bit surface  170 . Pressure applied to the micro core  175  by the contact with central drill bit surface  170  may contribute to producing the fracture  176  that separates micro core  175  from the remainder of formation  169 . In other embodiments, inner most cutters  173 A,  173 B may fracture the micro core  175  without and/or before the micro core  175  comes into contact with central drill bit surface  170  of drill bit  161 . 
     Once separated from formation  169 , a micro core such as micro core  175  may be urged upward through an escapeway  180  between blades  172 A and  172 B, for example by a fluid pressure generated by a fluid, such as drilling mud, that is being expelled from the drill bit  161  through one or more nozzles (not specifically shown in  FIG.  1 B , but for example one or more nozzles  256 ,  FIG.  2   ) in the drill bit. A fractured micro core generated by the operation of drill bit  161  may be urged to move along escapeway  180  in the direction indicated by arrow  181 , (as generally illustrated by micro core  182 ), toward annulus  166  located between borehole walls  164  and drill collar  162 , and be expelled at surface  163 . As micro core  175  is removed from the central area and/or bottom area of drill bit  161  and as drilling progresses, additional micro cores may be formed by inner most cutters  173 A,  173 B. These additional micro cores may then be fractured from formation  169 , and removed from the bottom area of drill bit  161  as described above. The ability of drill bit  161  to repeat the process of producing, fracturing, and removing micro cores from the bottom area of the drill bit  161  and the borehole terminus  167  may provide any of the features and advantages as described throughout this disclosure, such as more efficient drilling and/or the ability to determine a drilling/formation status as a result of and as related to micro core drilling and drill bits. 
       FIG.  2    is an isometric view of a fixed-cutter drill bit with cutters. In various embodiments, drill bit  200  may be similar to or the same as drill bit  101  as illustrated and described with respect to  FIG.  1 A . In various embodiments, drill bit  200  may be similar to or the same as drill bit  161  illustrated and described with respect to  FIG.  1 B . 
     Referring back to  FIG.  2   , drill bit  200  can be designed and formed in accordance with various embodiments and can have many different designs, configurations, and/or dimensions according to the particular application of the drill bit  200 . An uphole end  208  of the drill bit  200  can include a shank  210  with threads  211  formed thereon. In some embodiments, the threads  211  can be used to releasably engage the drill bit  200  with a BHA. For example, with reference to  FIG.  1 A , the threads  211  can releasably engage with the BHA  120 , whereby the drill bit  200  can rotate relative to a bit rotational axis  204 . In some embodiments, with reference to  FIG.  1 A , the bit rotational axis  204  can be the same as the bit rotational axis  104 . A downhole end  209  of the drill bit  200  can include a plurality of blades  202   a - 202   g  with respective junk slots or fluid flow paths disposed therebetween. Additionally, drilling fluids can be communicated via one or more nozzles  256 . 
     The plurality of blades  202  (e.g., blades  202   a - 202   g ) can be disposed outwardly from the exterior of a bit body  201  of the drill bit  200 . The bit body  201  can be generally cylindrical and the blades  202  can be any suitable type of projections extending outwardly (i.e. in a radial direction from the bit rotational axis  204 ) from the bit body  201 . For example, a portion of each blade  202  can be coupled to the exterior of the bit body  201 , while another portion of each blade  202  projects away from the exterior of the bit body  201 . The blades  202  can have a wide variety of configurations including, but not limited to, substantially arched, helical, spiraling, tapered, converging, diverging, symmetrical, and/or asymmetrical. 
     In some cases, one or more blades  202  can have a substantially arched configuration extending from proximate the bit rotational axis  204  of the drill bit  200 . The arched configuration can be defined in part by a generally concave, recessed shaped portion extending from a location proximate to the bit rotational axis  204 . The arched configuration can also be defined in part by a generally convex, outwardly curved blade portion disposed between the concave, recessed blade portion and outer portions of each blade which correspond generally with the outside diameter of the rotary drill bit. 
     The blades  202   a - 202   g  can include primary blades disposed about the bit rotational axis. For example, the blades  202   a ,  202   c , and  202   e  can be primary blades or major blades, wherein the inner end  212   a  of the blade  202   a , the blade  202   c , and the blade  202   e  can be disposed closely adjacent to the bit rotational axis  204  and closer to the bit rotational axis  204  than the remainder for the respective blades. The blades  202   a - 202   g  can also include at least one secondary blade (“minor blade”) disposed between the primary blades. Thus, the blades  202   b ,  202   d ,  202   f , and  202   g  shown in  FIG.  2    on the drill bit  200  can be secondary blades, wherein the inner end of a secondary blade is not as close to the bit rotational axis  204  as the inner end of a primary blade. For example, the inner ends  212   b  of the secondary blades  202   b ,  202   d ,  202   f ,  202   g  can be disposed on the downhole end  209  of the drill bit  200  at a distance from the bit rotational axis  204  that is at least 1.5 times, at least 2 times, at least 3 times, or between 1.5 and 5 times, between 2 and 5 times, or between 3 and 5 times, inclusive, of the distance of the farthest of inner ends  212   a  of the primary blades  202   a ,  202   c ,  202   e  from the bit rotational axis  204 . The number and location of secondary blades and primary blades can vary such that the drill bit  200  includes fewer or greater secondary and primary blades than are shown in  FIG.  2   , and the number of primary blades can be greater or less than the number of secondary blades. The blades  202  can be disposed symmetrically or asymmetrically with regard to each other and the bit rotational axis  204 , where the disposition can be based on the downhole drilling conditions of the drilling environment. 
     The inner ends  212   a  of the blades  202   a ,  202   c , and  202   e , are disposed closely adjacent to the bit rotational axis  204 . The inner ends  212   a , along with a portion of the bit body  201 , form a central bit surface  213 . During drilling, formation material adjacent the central bit surface  213  can either fracture and degrade with the surrounding formation during drilling, or it can form a short column of uncut formation. If a column of uncut formation is formed, the central bit surface  213  can crush or destroy the column of uncut formation as drilling progresses. In some embodiments, the column of uncut formation can be free from the drill bit  200  and can remain unmoved by circulation fluid that circulates solid material to the surface of the wellbore  107 . 
     The central bit surface  213  can be adapted to limit wear if it crushes or destroys uncut formation or as a result of drilling fluid flow. For example, portions of the central bit surface  213 , such as the inner ends  212   a , a portion of the bit body  201 , or an outer portion of the one or more nozzles  256 , can be formed from or layered with a superhard material, wherein a superhard material can be defined as any material having an abrasion toughness and/or fracture toughness that exceeds tungsten carbide. For example, superhard materials can include diamond, a PDC, and/or various hardened ceramic materials. Any two, a plurality of, or all of the inner ends  212   a  can have a longest distance from one another through the bit rotational axis  204  that is approximately between 0.0 and 0.5 inches. Alternatively, any two, a plurality of, or all of the inner ends  212   a  can have a longest distance from one another, as measured through the bit rotational axis  204 , that is between 0 and 1/10 the total diameter of the drill bit  101 . In drill bits wherein each of the inner ends of the blades are the same radial distance away from a bit rotational axis, the inner ends of any blades  202  attached to the bit  200  can be arranged and constructed in the same manner as the inner ends  212   a  as described herein. 
     The blades  202  and the drill bit  200  can rotate about the bit rotational axis  204  in the direction defined by directional arrow  205 . Each blade  202  can have a leading (or front) surface disposed on one side of the blade in the direction of rotation of the drill bit  200  and a trailing (or back) surface disposed on an opposite side of the blade away from the direction of rotation of the drill bit  200 . The blades  202  can be positioned along the bit body  201  such that they have a spiral configuration relative to the bit rotational axis  204 . Alternatively, the blades  202  can be positioned along the bit body  201  in a generally parallel configuration with respect to each other and the bit rotational axis  204 , as shown in  FIG.  2   . 
     The blades  202  include a set of cutters  203  disposed outwardly from outer portions of each blade  202 . For example, a portion of the set of cutters  203  can be projected away from the exterior portion of blade  202 . The set of cutters  203  may comprise any suitable device configured to cut into a formation, such as various types of compacts, buttons, inserts, and gage cutters known in the art to be used with a wide variety of fixed-cutter drill bits. 
     One or more of the cutters  203  can include a substrate with a layer of hard cutting material disposed on one end of the substrate  220 . The layer of hard cutting material may comprise a superhard material, such as a PDC material. The substrate may comprise carbide, such as tungsten carbide. With reference to  FIG.  1 A , the layer of hard cutting material can provide a cutting surface  214  for cutter  203 , a portion of which can engage adjacent portions of the formation to form a wellbore such as the wellbores  107   a ,  107   b . The contact of the cutting surface  214  with the formation can form a cutting zone associated with each cutter  203 . The edge of the cutting surface  214  located within the cutting zone can be referred to as the cutting edge of a cutter  203 . If cutter  203  has a cutting surface that is circular or circular in cross-section, then the cutting edge will have an arced portion referred to as the cutting arc. The length of the arced portion of the cutting edge is referred to as the cutting arc length. Cutter  203  can also include a side surface  215 . The cutters within the set of cutters  203  that are closest to one of the inner ends  212   a  can be considered innermost cutters. For example, cutter  243  is the closest cutter to one of the inner ends  212   a  relative to any other cutter on the blade  202   a , and can thus be considered as an innermost cutter. 
       FIG.  3    includes a set of profiles corresponding to the cutters and blades on a drill bit.  FIG.  3    includes a dashed box  300  and a dashed box  350 . The dashed box  300  shows a cutter profile  304 , blade profiles  305  and a set of cutters  322 - 327 . The blade profiles  305  correspond to the exterior surfaces of the blades near the cutters  322 - 327 . For example, with reference to  FIG.  2   , the blade profiles  305  can correspond to the exterior surfaces of the blades  202   a - 202   c . The set of cutters  322 - 327  includes the innermost cutter  322 . The innermost cutter  322  is located closest to the bit rotational axis  314  with respect to all of the cutters in the set of cutters  322 - 327 . Each of the innermost cutters can have a cutting arc that can comprise of either connected or disconnected segments from each other, wherein the cutting arc of a cutter can be the collective portion of a cutter surface boundary that cuts a formation during drilling. In some embodiments, the total cutting arc length of an example cutter can be less than a flat circular or oval cutting arc length that would be exhibited if the cutting surface of the example cutter were entirely circular or oval. 
     The innermost cutter  322  can include a flat surface  315  that is located within and interrupts the cutting arc  316  of the innermost cutter  322  such that the cutting arc has at least two portions located at opposite ends of the flat surface  315 . In addition, the innermost cutter  322  has a reduced cutting arc length as compared to a flat circular cutting arc length of a similar cutter with a cutting surface that is flat and/or entirely circular, such as the cutting surface of the cutter  327 . As a result, a combined track profile of a drill bit having the innermost cutter  322  can be reduced on the side adjacent to the bit rotational axis  314 , as shown by the innermost cutter  322 . The profile of the innermost cutter  322  can be circular throughout the majority of the profile, and non-circular in an area corresponding to the flat surface  315  on the side adjacent the bit rotational axis  314  and generally parallel to the bit rotational axis  314 , such that the non-circular profile can form an angle of within +/−3° of the bit rotational axis  314 , wherein the angle can be represented by the angle formed between the bit rotational axis  314  and the profile line  319 ). 
     The dashed box  350  shows a cutter profile  354 , blade profiles  355  and a set of cutters  372 - 377 . The blade profiles  355  correspond to the exterior surfaces of the blades near the cutters  372 - 377 . For example, with reference to  FIG.  2   , the blade profiles  355  can correspond to the exterior surfaces of the blades  202 . The set of cutters  372 - 377  includes the innermost cutter  372 . The innermost cutter  372  is located closest to the bit rotational axis  364  with respect to all of the cutters in the set of cutters  372 - 377 . 
     The innermost cutter  372  can include a relief  365  that is located within and interrupts its cutting arc  366  so that the cutting arc has at least two portions located at opposite ends of the relief  365 . In addition, the innermost cutter  372  has a reduced cutting arc length as compared to a flat circular cutting arc length of a similar cutter with a cutting surface that is both flat and entirely circular, such as the cutting surface of the cutter  377 . As a result, a drill bit having the innermost cutter  372  can have a track diagram in which the profile of the innermost cutter  372  is reduced on the side adjacent to the bit rotational axis  364 , as shown in the innermost cutter  372 . The profile of the innermost cutter  372  can be non-circular in an area corresponding to the relief  365  on the side adjacent the bit rotational axis  364  and its corresponding profile line  369  can form an acute angle with the uphole end of the bit rotational axis  364 . The acute angle can be greater than 3° and less than or equal to of 35°, or greater than 3° and less than or equal to 10°. While depicted with one relief  365 , the innermost cutter  372  can have multiple reliefs. The non-circular profile in an area corresponding to the relief  365  can include both curved and straight edges. 
     The non-circular cutter profiles in areas corresponding to the flat surface  315  or the relief  365  can reduce the surface area of their respective profiles as compared to circular cutter profiles. For example, the flat surface  315  and/or the relief  365  can reduce the surface area of their respective cutters  322 ,  372  by at least 5%, at least 10%, at least 30%, or by between 5% and 45%, between 5% and 30%, between 10% and 45%, between 10% and 30%, between 30% and 45%, inclusive. For example, the closest distance  307  between the innermost cutter  322  and the bit rotational axis  314  can be between 0 centimeters and five centimeters, inclusive. The closest distance  357  between the innermost cutter  372  and the bit rotational axis  364  can be between 0 centimeters and five centimeters, inclusive. In some embodiments, the closest distance  307  between the innermost cutter  322  and the bit rotational axis  364  can be a ratio up to 0.3 of the radius of the drill bit body. In some embodiments, the closest distance  357  between the innermost cutter  372  and the bit rotational axis  364  can be a ratio up to 0.3 of the radius of the drill bit body. 
     The innermost cutter  322 ,  372  can have a flattened cutting surface with a flat surface  315 , or relief  365  that can be wavy, angled, or curved. In addition, the innermost cutter  322 ,  372  can have more than one relief, allowing the cutter to be rotated in a socket in a drill bit once it is worn on one side, and after rotation, used to continue drilling without replacement of the innermost cutter  322 ,  372 . If the innermost cutter  322 ,  372  was rotated so that an alternate relief were located in the cutting area, then the alternate relief can have an associated and similar cutting arc length. In some embodiments, a cutter can have multiple reliefs, wherein each of the multiple reliefs have similar or identical geometry. In some embodiments, a different relief can be placed at regular intervals around the circumference of innermost cutter  322 . For example, a cutter can have reliefs with relief centers on opposite sides of the cutting surface (i.e. spaced radially 180 degrees from one another). As an additional example, a cutter can have three reliefs with relief centers spaced radially 120 degrees from one another. 
       FIG.  4 A  depicts a first view of an embodiment of a first innermost cutter.  FIG.  4 A  is a top view a cutter  400 , which can serve as an example of the innermost cutter  322  or the innermost cutter  372  of  FIG.  3   .  FIG.  4 B  is an isometric view of the cutter  400 . The cutter  400  includes a relieved cutting surface  414  having a first relief  416  and a second relief  456 . In some embodiments, the relieved cutting surface  414  can include one or more reliefs such that each relief creates an angle between the edge of the relief that defines a portion of the face, and the edge of the relief that defines a portion of the side of the cutter. The first relief  416  and the second relief  456  can have various shapes and dimensions. For example, each of the first relief  416  and the second relief  456  can start at approximately 10% of the radius from the center  434  of the relieved cutting surface  414  to the edge  431  at an angle between 1-5 degrees, wherein the radius can be the maximum distance  443  from the cutting surface center  434  to the cutting surface edge point  435 . 
     The first relief  416  can have a maximum radial distance  421  from a circular or oval cutting surface edge that would be present if the cutting surface  414  were entirely circular or oval. In some embodiments, the maximum radial distance  421  can be between ¼ and 4/4 inclusive, or between ⅓ and 4/4, inclusive of the radius or major axis of the cutting surface  414  absent the relief. The second relief  456  can have a similar maximum radial distance. The relieved cutting surface  414  can have a total cutting arc length equal to the sum of the length of the two circular portions  418  and  419 . In some embodiments, the total cutting arc length can be less than a flat circular or oval cutting arc length that would be exhibited if the cutting surface  414  were entirely circular or oval. 
     The relieved cutting surface  414  can be flattened and circular or oval over the majority of cutting surface  414 , with the exception of a first relief  416  and a second relief  456 , which are located within and interrupt the cutting arc of the cutter  400 . In this example, the first relief  416  is nonlinear and includes a curved edge  404 , a straight edge  406 , a curved edge  408 , and a curved edge  410 . The curved edge  404  can be convex relative to the center of the innermost cutter  400  and can be positioned at a first end of the first relief  416 . 
     A first end of the curved edge  408  can be positioned adjacent to the straight edge  406  (at an end that is opposite the end of straight edge  406  that is adjacent to the curved edge  404 ). Additionally, a second end of the curved edge  408  is positioned at a first end of the curved edge  410 . A second end of the curved edge  410  can be positioned at a second end of the first relief  416 . The curved edge  408  can fracture a micro core that has been formed by the cutter  400  under side load to failure. Additionally, similar to the curved edge  404 , the curved edge  408  and the curved edge  410  can cooperate to increase the toughness of the cutter  400 . In some embodiments, the micro core can be rock material having a diameter that is between 10 and 40 millimeters. In some embodiments, the micro core can be rock material having a diameter based on a ratio of the radius of the drill bit used to form the micro core. 
     The first relief  416  can include a modified edge that reduces the arc length of rock engagement to create a micro core. The contour of the first relief  416  can increase edge toughness based on the curved edge  404 , wherein the contour of the first relief  416  is structured in an order comprising a curved contour portion, straight contour portion, and curved contour portion. The straight edge  406  of the first relief  416  can also reduce the rock being drilled to generate a micro core. The curved edge  408  of the contour of the first relief  416  can also operate to fracture the micro core. In some embodiments, the height of the micro core can be dependent on the length of the straight edge. The first relief  416  can have a maximum radial distance  421  from a circular or oval cutting surface edge that would be present if the cutting surface  414  were entirely circular or oval, that is between ⅕ and ⅘ inclusive, or between ⅓ and ⅘, inclusive of the radius or major axis of the cutting surface  414  absent the relief. 
     The curved edge  408  and the curved edge  404  can increase the toughness of the cutter  400  by distributing stress from the loading of the cutter  400  during drilling operations. The straight edge  406  can be positioned adjacent to the curved edge  404 . The straight edge  406  can be positioned in the first relief  416  to create a mini core of the rock from the formation being cut. In some embodiments, a length of the straight edge  406  is proportional to a diameter of the cutter  400 . For example, if the diameter of the cutter  400  increases to be two times larger, the length of the straight edge  406  can also be increased to be two times larger. 
     The cutter  400  includes the second relief  456 . The second relief  456  can be dimensioned and arranged similar to the first relief  416 , or as a mirror image of the first relief  416 . Accordingly, instead of replacing the cutter  400  when the relief  416  is damaged, the cutter  400  can be rotated 180 degrees so that the second relief  456  is positioned in place of the first relief  416 . The second relief  456  then becomes the active relief. The second relief  456  can be nonlinear and can include a curved edge  464 , a straight edge  466 , a straight edge  468 , and a curved edge  470 . 
     In some embodiments, the second relief  456  can include a modified edge that reduces the arc length of rock engagement to create a micro core during drilling operations. Accordingly, the contour of the second relief  456  can increase the toughness of the edge as a result of cooperation between the curved edges  464  and  470 . The contour of the second relief  456  can reduce the rock being drilled to a micro core via cutting forces applied by the straight edge  466 . The contour of the second relief  456  can also operate to fracture the micro core under side load generated by the straight edge  468 . While the sections of the cutting surface  414  not intersected by the reliefs  416  and  456  are shown as circular, relieved cutting surface  414  can be ovoid in some embodiments. 
     In some embodiments, the curved edge  464  can be convex and can be positioned at a first end of the second relief  456 . The straight edge  468  can increase the toughness of the cutter  400  to reduce cracking of the cutter  400  during drilling operations. The straight edge  466  can be positioned adjacent to the curved edge  464 . The straight edge  466  can be positioned in the second relief  456  to create a mini core from the rock of the formation being cut. In some embodiments, a length of the straight edge  466  is proportional to a diameter of the cutter  400 . For example, if the diameter of the cutter  400  is doubled, the length of the straight edge  466  can also be doubled. 
     A first end of the straight edge  468  can be positioned adjacent to the straight edge  466 , wherein the first end of the straight edge  468  can be at an end that is opposite to the end that is adjacent to the curved edge  464 . Additionally, a second end of the straight edge  468  can be positioned at a first end of the curved edge  470 . A second end of the curved edge  470  can be positioned at a second end of the second relief  456 . The curved edge  466  and/or the curved edge  408  can operate to fracture the generated micro core under side load to failure. Additionally, similar to the curved edge  464 , the straight edge  468  and the curved edge  470  can provide additional toughness for the cutter  400 , wherein a curved edge can be used instead of a straight edge at the position of the straight edge  468 . 
     Although the cutter  400  is depicted as having a flattened cutting surface for which the cutting arc length or the surface area can be compared to having a portion of a circle or an oval, other portions of flattened cutting surface shapes, such as a portion of a polygon can be used in place of a circle or an oval. Alternatively, or in addition, an innermost cutter can have an irregular flattened cutting surface with a reduced cutting arc length or a reduced surface area. The cutting arc length for an innermost cutter can be compared to what it would be as calculated using a best fit cutting arc length of a best fit circle, oval, or polygon with less than ten sides for the flattened cutting surface absent the relief. For these above comparisons, the cutting arc length or surface area of the flattened cutting surface can be reduced by at least 5%, at least 10%, at least 20%; or by between 5% and 45%, between 5% and 30%, between 5% and 20%, between 10% and 45%, between 10% and 30%, between 20% and 30%, between 20% and 45%, or between 20% and 30%, inclusive as compared to the surface area of the best fit circle, oval, or polygon with less than ten sides absent the relief or reliefs. 
     The relief can extend laterally only through a portion of the layer of hard cutting material such as PDC, or it can extend laterally through all of the hard cutting material. If the relief extends laterally through all of the hard cutting material, it can then extend laterally through none, a portion of, or all of the substrate. In general, lateral extension of the relief through at most a portion of the substrate can facilitate attachment of the innermost cutter to a fixed-cutter drill bit by allowing the use of a circular pocket if the innermost cutter is circular in radial cross-section. However, extension of the relief through all of the substrate, coupled with a pocket having a wall that matches the shape of the relief, can facilitate proper placement of the innermost cutter with respect to the rotational axis of the bit. The relief can extend linearly and axially through the innermost cutter, so that it is at an approximately ninety-degree angle with respect to the cutting surface. The relief can also extend linearly at an obtuse angle with respect to the cutting surface. The relief  416  can also extend non-linearly in a shape, such as a curve, which generally forms an obtuse angle (as shown in  FIG.  4 A ) with respect to the cutting surface  414 . 
     Embodiments of cutter  400  may include a plurality of reliefs, for example but not limited to a set of two reliefs such as reliefs  416  and  456  as described above and as illustrated with respect to  FIGS.  4 A and  4 B . Other embodiments of a cutter may include a cutter having just one single relief.  FIG.  5    illustrates an example cutter  400 A comprising a single relief  416 . As shown in  FIG.  5   , cutter  400 A includes the single relief  416  having a radial distance  421  that interrupts the circular or oval cutting surface edge  431  that would otherwise be continuously round or oval in shape if not for the presence of the relief  416 . Relief  416  may include one or more, or any combination of, the elements described above with respect to relief  416  of cutter  400  and  FIGS.  4 A and  4 B , and may be configured to perform one or more, or any combination of the functions ascribed to cutter  400 . 
       FIGS.  6 - 7    depict views of a second innermost cutter.  FIG.  6    includes a dashed box  690  and a dashed box  691 .  FIG.  7    includes a dashed box  700  and a dashed box  701 . The dashed box  690  includes a schematic cutting view of an innermost cutter  600 . The dashed box  691  includes a schematic elevation view of the innermost cutter  600 . The dashed box  700  depicts a schematic cross-sectional view of the innermost cutter  600 . The dashed box  701  depicts a schematic isometric view of the innermost cutter  600 . The innermost cutter  600  can be a cutter closest to a bit rotational axis. For example, with reference to  FIG.  3   , the innermost cutter  600  can be positioned at the position of the innermost cutter  322 . 
     The innermost cutter  600  can have a wavy profile that extends inwards relative to the maximum radius of a flattened cutting surface  614  covering a substrate  620 . In some embodiments, the innermost cutter  600  includes a circular portion  628  representing a circular portion of the innermost cutter  600  that comprises the substrate  620  but does not comprise the cutting surface  614 . The flattened cutting surface  614  can have an edge  619 , wherein the edge  619  can include both straight edge portions and flat edge portions. In some embodiments, reliefs  616  of the innermost cutter  600  can have a maximum radial distance  621  from a circular or oval cutting surface edge that would be present if the cutting surface  614  were entirely circular or oval. In some embodiments, the maximum radial distance  621  can be between ⅕ and ⅘ inclusive, or between ⅓ and ⅘, inclusive of the radius or major axis of the cutting surface  614  absent the reliefs  616 . 
     The reliefs  616  can reduce the surface area of the flattened cutting surface  614  as compared to what the flattened cutting surface  614  would be if the flattened cutting surface  614  were entirely circular or oval. In some embodiments, the surface area of a cutting surface can be reduced relative to an entirely circular or oval cutting surface by at least 5%, at least 10%, at least 20%, or by between 5% and 45%, between 5% and 30%, between 5% and 20%, between 10% and 45%, between 10% and 30%, between 20% and 30%, between 20% and 45%, or between 20% and 30%, inclusive. For example, the reliefs  616  can reduce the surface of the flattened cuttings surface  614  by 30%. In some embodiments, the least length between the cutting surface  614  and the surface center  634  can be represented by the distance  618 . 
       FIG.  8    includes views of a third innermost cutter and a fourth innermost cutter.  FIG.  8    includes a dashed box  890  and a dashed box  891 , wherein the dashed box  890  is a schematic cutting view of a third innermost cutter  800 , and wherein the dashed box  891  is a schematic cutting view of a fourth innermost cutter  850 . The third innermost cutter  800  includes reliefs  816  having a curved profile that curve inwards with respect to a maximum radius of a cutting surface  814 , wherein the maximum radius can be represented as the line  803  between a surface center  804  and the edge point  805  of the cutting surface  814 . As shown in  FIG.  8   , the reliefs  816  of the third innermost cutter  800  can be centered on approximately opposite sides of the cutting surface  814  and can extent into or stop at the substrate  820 . The third innermost cutter  800  can also include a combined cutting arc length comprising the first circular portion  818  and the second circular portion  819 . In some embodiments, the third innermost cutter  800  includes a circular portion  828  representing a circular portion of the third innermost cutter  800  that comprises the substrate  820  but does not comprise the cutting surface  814 . 
     The fourth innermost cutter  850  depicted in the dashed box  891  includes three reliefs  866 , each having a curved profile that curves inwards with respect to a maximum radius of the cutting surface  864 , wherein the maximum radius can be represented as the line  853  between a surface center  854  and the edge point  855 . As shown in  FIG.  8   , the three reliefs  866  of the fourth innermost cutter  850  can be spaced radially around the fourth innermost cutter  850 . The fourth innermost cutter  850  also includes a combined cutting arc length comprising the first circular portion  868  and the second circular portion  869 . A substrate  870  can be below the cutting surface  864 . In some embodiments, the fourth innermost cutter  850  includes a circular portion  878  representing a circular portion of the fourth innermost cutter  850  that comprises the substrate  870  but does not comprise the cutting surface  864 . 
       FIG.  9    is a view of a fifth cutter.  FIG.  9    includes a fifth innermost cutter  900 . The fifth innermost cutter  900  includes reliefs  916 . The reliefs  916  can be angled and can have two linear portions that meet at an angle  937 . In some embodiments, the angle  937  can be between 100 degrees and 170 degrees inclusive. In some embodiments, the angle  937  can be less than 100 degrees or greater than 170 degrees. As shown in  FIG.  9   , the reliefs  916  of the fifth innermost cutter  900  can be centered on approximately opposite sides of the cutting surface  914 . The fifth innermost cutter  900  also includes a combined cutting arc length comprising the first circular portion  918  and the second circular portion  919 . A substrate  920  can be below the cutting surface  914 . In some embodiments, the fifth innermost cutter  900  includes a circular portion  928  representing a circular portion of the fifth innermost cutter  900  that comprises the substrate  920  but does not comprise the cutting surface  914 . 
       FIG.  10    is a top view of a first example bottom hole pattern formed as a result of the drilling with a drill bit having an innermost cutter.  FIG.  10    depicts a first bottom hole pattern  1000 . The first bottom hole pattern  1000  shows spiral tubes  1002  centered around a microcore center  1006 . The spiral tubes  1002  can represent cutter paths formed by rotation of a drill bit during a drilling operation. As shown in the first bottom hole pattern  1000 , the cutter paths represented by the spiral tubes  1002  avoid the microcore center  1006 . With respect to  FIG.  2   ,  FIGS.  4 A,  4 B , and  FIGS.  5 - 9   , the drill bit  200  having one or more innermost cutters similar to or the same as the cutters  400 ,  600 ,  800 , and/or  900  can be used to generate the first bottom hole pattern  1000 . 
       FIG.  11    is a top view of second example bottom hole pattern formed as a result of the drilling with a drill bit having an innermost cutter.  FIG.  11    depicts a second bottom hole pattern  1100 . The second bottom hole pattern  1100  shows spiral tubes  1102  centered around a microcore center  1106 . The spiral tubes  1102  can represent cutter paths formed by rotation of a drill bit during a drilling operation. As shown in the second bottom hole pattern  1100 , the cutter paths represented by the spiral tubes  1102  avoid the microcore center  1106 . With respect to  FIG.  2   ,  FIGS.  4 A,  4 B , and  FIGS.  5 - 9   , the drill bit  200  having one or more innermost cutters similar to or the same as the cutters  400 ,  600 ,  800 , and/or  900  can be used to form the second bottom hole pattern  1100 . 
       FIG.  12    is an isometric view of a third example bottom hole pattern formed as a result of the drilling with a drill bit having an innermost cutter.  FIG.  12    depicts a third bottom hole pattern  1200  surrounded by a portion of a rock formation  1201 . The third bottom hole pattern  1200  shows spiral tubes  1202  centered around a microcore center  1206 . In addition, the third bottom hole pattern  1200  includes cutter positions represented by the cylinders  1222 . The spiral tubes  1202  can represent paths that cutters follow during rotation of a drill bit during drilling operations. As shown in the third bottom hole pattern  1200 , the cutter paths represented by the spiral tubes  1202  avoid the microcore center  1206 . With respect to  FIG.  2   ,  FIGS.  4 A,  4 B , and  FIGS.  5 - 9   , the drill bit  200  having one or more innermost cutters similar to or the same as the cutters  400 ,  600 ,  800 , and/or  900  can be used to form the third bottom hole pattern  1200 . 
       FIG.  13    includes a flowchart  1300  illustrating a method according to various embodiments of the disclosure. Embodiments of the method include operating a drill bit configured to generate micro cores while extending a borehole into a formation material (block  1302 ). The drill bit may include any of the embodiments of a drill bit configured to generate a micro core as described throughout this disclosure, and any equivalents thereof. For example, embodiments of the drill bit may include inner most cutters that include one or more reliefs configured according to any of the embodiments of reliefs as described throughout the disclosure, and/or any equivalents thereof. For example, the innermost cutter may include a relief on the cutting material of the cutting surface, wherein at least one end of the relief is located at and interrupts a cutting arc. The relief can be formed in various indented shapes, such as a linear indentation, a curved groove, etc. The relief can include various specific shapes. For example, the relief can include a first curved edge, followed by a straight edge, followed by a second curved edge, wherein a curved edge can be any edge wherein two sides of the cutting surface material are at an angle less than zero. In some embodiments, the first curved edge and the second curved edge can cooperate to increase the edge toughness of the cutting surface. In some embodiments, drilling using a straight edge of the relief results in the generation of a micro core using the drill bit. The second curved edge can operate to fracture the micro core under the side load of the drill bit. Additionally, in some embodiments, the cutting arc of engagement between an innermost cutter of the drill bit and a formation can be longer than any other cutters on the drill bit. 
     Embodiment of the method may include fracturing a micro core generated by the drilling operation from the formation material (block  1304 ). Fracturing the micro core in various embodiments includes fracturing the micro core as a result of side load force(s) exerted on the micro core by one more inner cutters included on the drill bit performing the drilling operation that is generating the micro cores. Fracturing the micro core in various embodiments includes fracturing the micro cores as a result of a force exerted by a central drill bit surface (e.g., central drill bit surface  170 ,  FIG.  1 B ) on the micro core. In various embodiments, fracturing of the micro core may including fracturing the micro core as a result of a combination of side load force(s) exerted on the micro core by one more inner most cutters included on the drill bit and force(s) exerted on the micro core as a result of direct contact between the micro core and a central drill bit surface of the drill bit. 
     Embodiments of the one or more methods may include urging a fractured micro core away from a bottom portion or area of the drill bit performing the drilling operation. Urging of the micro core away from a bottom portion or area of the drill bit may include urging the fractured micro core along an escapeway formed between one or more blades of the drill bit. Urging the micro core away from the bottom portion or area of the drill bit may include using a flow of a fluid, such as a drilling fluid, to urge the fractured micro core away from the bottom portion or area of the drill bit. Urging the micro core away from the bottom portion or area of the drill bit in various embodiments includes conveying, for example using a fluid, the fractured micro core to a top surface and out of the borehole thru an annulus area between a drill string coupled to the drill bit and a borehole wall of the borehole. In various embodiments, the process of generating a micro core by operating the drill bit in a drilling operation, fracturing the micro core, and urging the micro core away from the bottom portion or area of the drill bit may be repeated for any number of cycles as the drilling operation is being performed, as represented by the arrow  1308  coupling block  1306  back to block  1302 . 
     Embodiments of the method may include capturing the fractured micro core (block  1310 ) and performing an inspection, testing, or other forms of analysis on the captured micro core (block  1312 ). Capturing the fracture micro core may include catching the micro core in a screening device configured to allow a fluid, such as drilling fluid, to pass through the screening device but to block and capture the micro core(s) being transported by the fluid. Inspection, testing, and/or other types of analysis of the captured micro core(s) may include any type of testing, including visual inspections by an operator such as an engineer or technician, and/or other types of testing, such as chemical analysis, X-ray analysis, imaging of the micro core using any type of imaging equipment, or any other form(s) of analysis that may be used to determine one or more physical properties present in the micro core. 
     Throughout the application, plural instances may be provided for components, operations or structures described herein as a single instance. Finally, boundaries between various components, operations and data stores are somewhat arbitrary, and particular operations are illustrated in the context of specific illustrative configurations. Other allocations of functionality are envisioned and may fall within the scope of the disclosure. In general, structures and functionality presented as separate components in the example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the disclosure. 
     As used herein, the term “or” is inclusive unless otherwise explicitly noted. Thus, the phrase “at least one of A, B, or C” is satisfied by any element from the set {A, B, C} or any combination thereof, including multiples of any element. A set of items can have only one item or more than one item. For example, a set of numbers can be used to describe a single number or multiple numbers. 
     Example embodiments of the drill bit and the methods for using a drill bit as described herein may include the following. 
     Embodiments of the disclosure can include an drill bit comprising a bit body defining a bit rotational axis, a blade attached to the bit body, and a cutter comprising a cutting arc on a cutting surface of the cutter, wherein the cutter comprises at least one relief comprising a straight edge and a curved edge having an end that interrupts the cutting arc. In some embodiments, the cutter is an innermost cutter, wherein the innermost cutter is closer to the bit rotational axis than a second cutter mounted on the blade. In one or more of the embodiments above, the curved edge is convex with respect to a center of the cutter. In one or more of the embodiments above, the curved edge is a first curved edge, and wherein the at least one relief comprises a second curved edge. In one or more of the embodiments above, the second curved edge is concave with respect to a center of the cutter. In one or more of the embodiments above, a length of the straight edge is proportional to a diameter of the cutter. In one or more of the embodiments above, the first curved edge has a first end positioned at a first end of the at least one relief, wherein the straight edge has a first end adjacent to a second end of the first curved edge, and wherein the second curved edge has a first end adjacent to a second end of the straight edge, wherein a second end of the second curved edge is positioned at a second end of the at least one relief. 
     Embodiments of the disclosure can include a system comprising a drill string, a fixed-cutter drill bit attached to the drill string, wherein the fixed-cutter drill bit comprises a bit body defining a bit rotational axis, a blade attached to the bit body, and a cutter comprising a cutting arc on a cutting surface of the cutter, wherein the cutter comprises at least one relief comprising a straight edge and a curved edge having an end that interrupts the cutting arc. In one or more of the embodiments above, the curved edge is convex. In one or more of the embodiments above, a length of the straight edge is proportional to a diameter of the cutter. In one or more of the embodiments above, the curved edge is a first curved edge, and wherein the at least one relief comprises a second curved edge. In one or more of the embodiments above, the first curved edge has a first end positioned at a first end of the at least one relief, wherein the straight edge has a first end adjacent to a second end of the first curved edge, and wherein the second curved edge has a first end adjacent to a second end of the straight edge, wherein a second end of the second curved edge is positioned at a second end of the at least one relief. In one or more of the embodiments above, the second curved edge is concave. 
     Embodiments of the disclosure may include a method comprising: operating a drill bit to generate one or more micro cores as part of a drilling process used to extend a borehole into a foundation material, wherein the drill bit comprises a bit body defining a bit rotational axis, a blade attached to the bit body, and a cutter comprising a cutting arc on a cutting surface of the cutter, wherein the cutter comprises at least one relief comprising a straight edge and a curved edge having an end that interrupts the cutting arc. Embodiments of the method may further comprise fracturing each of the one or more micro cores by applying a side load pressure generated by the cutter arc and applied to a side portion of each of the one or more micro cores as each micro core is generated by operating the drill bit; and after fracturing a given micro core of the one or more micro cores, urging the given micro core away from a terminus area of the drill bit. Embodiments of the method may further comprise capturing the fractured micro core and performing testing or other types of analysis on the captured micro core. 
     Embodiments of the invention can include a cutter and use of a cutter to form micro core in foundation rock, comprising a cutting surface, a cutting arc, and at least one relief having an end that interrupts the cutting arc, wherein the at least one relief comprises a straight edge and a curved edge having an end that interrupts the cutting arc. In one or more of the embodiments above, a length of the straight edge is proportional to a diameter of the cutter. In one or more of the embodiments above, the at least one relief is a first relief, and wherein the cutter comprises a second relief and a third relief, wherein each of the second relief and the third relief comprise a respective curved edge and a respective straight edge. In one or more of the embodiments above, the curved edge is a first curved edge, and wherein the cutter comprises a second curved edge. In one or more of the embodiments above, the second curved edge is concave. In one or more of the embodiments above, the first curved edge has a first end positioned at a first end of the at least one relief, wherein the straight edge has a first end adjacent to a second end of the first curved edge, and wherein the second curved edge has a first end adjacent to a second end of the straight edge, wherein a second end of the second curved edge is positioned at a second end of the at least one relief. In one or more of the embodiments above, the first curved edge is convex and the second curved edge is concave.