Patent Publication Number: US-10760346-B2

Title: Rotatable cutters and elements, earth-boring tools including the same, and related methods

Description:
TECHNICAL FIELD 
     Embodiments of the present disclosure generally relate to devices and methods involving cutting and other rotatable elements for earth-boring tools used in earth boring operations and, more specifically, to cutting elements for earth-boring tools that may rotate in order to alter the rotational positioning of the cutting edge and cutting face of the cutting element relative to an earth-boring tool to which the cutting element is coupled, to earth-boring tools so equipped, and to related methods. 
     BACKGROUND 
     Various earth-boring tools such as rotary drill bits (including roller cone bits and fixed-cutter or drag bits), core bits, eccentric bits, bi-center bits, reamers, and mills are commonly used in forming bore holes or wells in earth formations. Such tools often may include one or more cutting elements on a formation-engagement surface thereof for removing formation material as the earth-boring tool is rotated or otherwise moved within the borehole. 
     For example, fixed-cutter bits (often referred to as “drag” bits) have a plurality of cutting elements affixed or otherwise secured to a face (i.e., a formation-engagement surface) of a bit body. Cutting elements generally include a cutting surface, where the cutting surface is usually formed out of a superabrasive material, such as mutually bound particles of polycrystalline diamond. The cutting surface is generally formed on and bonded to a supporting substrate of a hard material such as cemented tungsten carbide. During a drilling operation, a portion of a cutting edge, which is at least partially defined by the peripheral portion of the cutting surface, is pressed into the formation. As the earth-boring tool moves relative to the formation, the cutting element is dragged across the surface of the formation and the cutting edge of the cutting surface shears away formation material. Such cutting elements are often referred to as “polycrystalline diamond compact” (PDC) cutting elements, or cutters. 
     During drilling, cutting elements are subjected to high temperatures due to friction between the cutting surface and the formation being cut, high axial loads from the weight on bit (WOB), and high impact forces attributable to variations in WOB, formation irregularities and material differences, and vibration. These conditions can result in damage to the cutting surface (e.g., chipping, spalling). Such damage often occurs at or near the cutting edge of the cutting surface and is caused, at least in part, by the high impact forces that occur during drilling. Damage to the cutting element results in decreased cutting efficiency of the cutting element. When the efficiency of the cutting element decreases to a critical level the operation must be stopped to remove and replace the drill bit which is a large expense for an operation utilizing earth-boring tools. 
     Securing a PDC cutting element to a drill bit restricts the useful life of such cutting element. As the cutting edge of the diamond table and the substrate wear down a so-called “wear flat” is created necessitating increased weight on bit to maintain a given rate of penetration of the drill bit into the formation due to the increased surface area presented. In addition, more than half of the cutting element is never used unless the cutting element is heated to remove it from the bit and then rebrazed with an unworn portion of the cutting edge presented for engaging a formation. 
     Attempts have been made to configure cutting elements to rotate such that the entire cutting edge extending around each cutting element may selectively engage with and remove material. By utilizing the entire cutting edge, the effective life of the cutting element may be increased. Many designs for rotating cutting elements allow the cutting element to freely rotate even when under a cutting load. Rotating under a load results in wear on internal surfaces exposing the cutting element to vibration which can damage the cutting elements reducing their life, and may result in uneven wear on the cutting edge of the cutting element. 
     BRIEF SUMMARY 
     In some embodiments, the present disclosure includes a rotatable cutter for use on an earth-boring tool. The rotatable cutter may comprise a rotatable element and a stationary element. The rotatable element may include a cutting surface and a first interface surface on respective sides of a support structure. The stationary element may be coupled to the rotatable element. The rotatable element may be configured to move relative to the stationary element along a longitudinal axis of the rotatable cutter. The stationary element may have a second interface surface. The first interface surface of the rotatable element and the second interface surface of the stationary element may define a releasable interface. The releasable interface may be configured to substantially inhibit rotation of the rotatable element when the two surfaces are at least in partial contact. 
     In additional embodiments, the present disclosure includes an earth-boring tool. The earth-boring tool may have at least one rotatable element fixed thereto. The rotatable element comprises a movable element, a sleeve element, and an engagement feature. The movable element may include a surface to engage a portion of a subterranean borehole, and a shoulder. The movable element may be at least partially disposed within the sleeve element, and configured to “float” over the sleeve element in a direction along a longitudinal axis of the movable element. The movable element may also rotate about the longitudinal axis of the rotatable element. There may be at least a portion of the movable element spaced from the sleeve element. The engagement feature may be positioned on at least one of the shoulder of the movable element or the sleeve element. The engagement feature may be configured to at least partially inhibit rotation of the movable element relative to the sleeve element when the shoulder of the movable element contacts the sleeve element. 
     Further embodiments of the present disclosure include a method for at least partially inhibiting the rotation of a rotatable cutting element on an earth-boring tool. The method includes moving a cutting element along a longitudinal axis of the rotatable cutting element within a sleeve element. A first engagement surface of the cutting element may be engaged with a second engagement surface of the sleeve element. The cutting element may be arrested by at least one of a frictional engagement or an interference engagement between the first engagement surface and the second engagement surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the specification concludes with claims particularly pointing out and distinctly claiming embodiments of the present disclosure, the advantages of embodiments of the disclosure may be more readily ascertained from the following description of embodiments of the disclosure when read in conjunction with the accompanying drawings in which: 
         FIG. 1  illustrates a fixed-cutter earth-boring tool commonly known as a “drag-bit,” in accordance with embodiments of the present disclosure; 
         FIG. 2  is an isometric view of a rotatable cutter in accordance with an embodiment of the present disclosure; 
         FIG. 3  is an exploded view of a rotatable cutter in accordance with embodiments of the present disclosure; 
         FIG. 4  is an exploded view of a rotatable cutter in accordance with another embodiment of the present disclosure; 
         FIG. 5A  is an isometric view of a stationary element in accordance with an embodiment of the present disclosure; and 
         FIG. 5B  is an isometric view of a movable element in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The illustrations presented herein are not meant to be actual views of any particular earth-boring tool, rotatable cutting element or component thereof, but are merely idealized representations employed to describe illustrative embodiments. The drawings are not necessarily to scale. 
     Disclosed embodiments relate generally to rotatable elements (e.g., cutting elements) for earth-boring tools that may rotate in order to alter the positioning of the cutting element relative to an earth-boring tool to which the cutting element is coupled. For example, such a configuration may enable the cutting element to present a continuously sharp cutting edge with which to engage a downhole formation while still occupying substantially the same amount of space as conventional fixed cutting elements. Some embodiments of such rotatable cutting elements may include a stationary element, a rotatable element, and a releasable interface between a surface of the rotatable cutting element and a surface of the stationary element. The releasable interface may act to substantially inhibit the rotatable cutting element from rotating relative to the stationary element when the surface of the rotatable cutting element is in contact with the surface of the stationary element. 
     Such rotatable elements may be implemented in a variety of earth-boring tools, such as, for example, rotary drill bits, percussion bits, core bits, eccentric bits, bi-center bits, reamers, expandable reamers, mills, drag bits, roller cone bits, hybrid bits, and other drilling bits and tools known in the art. 
     As used herein, the term “substantially” in reference to a given parameter means and includes to a degree that one skilled in the art would understand that the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances. For example, a parameter that is substantially met may be at least about 90% met, at least about 95% met, or even at least about 99% met. 
     Referring to  FIG. 1 , a perspective view of an earth-boring tool  10  is shown. The earth-boring tool  10  may have blades  20  in which a plurality of cutting elements  100  may be secured. The cutting elements  100  may have a cutting table  101  with a cutting surface  102 , which may form the cutting edge of the blade  20 . The earth-boring tool  10  may rotate about a longitudinal axis of the earth-boring tool  10 . When the earth-boring tool  10  rotates, the cutting surface  102  of the cutting elements  100  may contact the earth formation and remove material. The material removed by the cutting surfaces  102  may then be removed through the junk slots  40 . The earth-boring tool  10  may include nozzles  50 , which may introduce drilling fluid, commonly known as drilling mud, into the area around the blades  20  to aid in removing the sheared material and other debris from the area around the blades to increase the efficiency of the earth-boring tool  10 . 
     In applications where the cutting elements  100  are fixed, only the edge of the cutting surface  102  of the cutting elements  100  that is exposed above the surface of the blade  20  will contact the earth formation and wear down during use. By rotating the cutting element  100 , relatively more of (e.g., a majority of, a substantial entirety of) the edge of the cutting surface  102  may be exposed to wear and may act to extend the life of the cutting element  100 . 
     In applications where the cutting elements  100  are allowed to rotate while actively engaging the earth formation wear may occur on the internal parts of the cutting elements  100 . Internal wear may impede rotation or cause vibration, both of which may cause the cutting element  100  to fail prematurely. Inhibiting the rotation of the cutting element  100  while the cutting element  100  is actively engaging the earth formation, in accordance to embodiment disclosed herein, may further extend the life of the cutting element  100 . 
     Referring to  FIG. 2 , a perspective view of an embodiment of a rotatable cutting element  100  is shown. The rotatable cutter  100  may comprise the cutting table  101  with the cutting surface  102  and a substrate  108 . The rotatable cutter  100  may be secured to the earth-boring tool  10  ( FIG. 1 ) by fixing the exterior surface of the substrate  108  to the earth-boring tool  10 . This is commonly achieved through a brazing process. 
     Referring to  FIG. 3 , an exploded view of an embodiment of a rotatable cutter  100  is shown. The rotatable cutter  100  may include at least two components. For example, the rotatable cutter  100  may comprise a cutting element  104  portion (e.g., a rotatable element, a movable element, a cutting element portion) and a stationary element  106  (e.g., a sleeve element). The cutting element  104  may be disposed at least partially within the stationary element  106 . 
     In some embodiments, the rotatable element  104  may comprise a surface configured to engage a portion of a subterranean borehole (e.g., a cutting surface  102 ), a support structure  110 , and a shoulder  112  (e.g., first interface surface, or first engagement surface). The cutting surface  102  may be formed from a polycrystalline material, such as, polycrystalline diamond or polycrystalline cubic boron nitride. The support structure  110  of the rotatable element  104  may be formed from a hard material suitable for use in a subterranean borehole, such as, for example, a metal, alloy (e.g., steel), or ceramic-metal composite (e.g., cobalt-cemented tungsten carbide). The cutting surface  102  may be positioned on a first side of the support structure  110 , such that the cutting surface  102  may engage a portion of the subterranean borehole. The shoulder  112  may be positioned on a second side of the support structure  110 , opposite the cutting surface  102 . In some embodiments, the cutting surface  102  may be larger in diameter than the base  120  of the rotatable element  104 . In some embodiments, the support structure  110  may be the same diameter as the cutting surface  102 . The shoulder  112  may exhibit a chamfered (e.g., tapered, or conical) surface between the larger diameter of the support structure  110  and the smaller diameter of the base  120 . In some embodiments, at least a portion of the shoulder  112  may be substantially parallel (e.g., not tapered) to the cutting surface  102 . For example, a shoulder surface  113  may extend around the outer circumference of the shoulder  112 . The parallel shoulder surface  113  may rest against a top surface  115  of the stationary element  106  when the rotatable element  104  is fully disposed within the stationary element  106 . In some embodiments, a majority of (e.g., a substantial entirety of, more than half of) the shoulder  112  may comprise the parallel shoulder surface  113 . In some embodiments, the majority of the shoulder  112  may comprise a chamfered surface, as demonstrated in  FIG. 3 . 
     In some embodiments, the stationary element  106  may be formed from a hard material, such as, for example, a metal, alloy, or ceramic-metal composite. The stationary element  106  may define a void  114  (e.g., a cavity, or a bore). The stationary element  106  may have a second interface surface  116  (e.g., a second engagement surface). The second interface surface  116  may come into contact with the shoulder  112  of the rotatable element  104 . The second interface surface  116  may be complementary to the surface of the shoulder  112 . For example, the second interface surface  116  may have a complementary chamfer (e.g., taper, conical shape) to the surface of the shoulder  112 . 
     In some embodiments, the stationary element  106  and the rotatable element  104  may be coupled to one another by any suitable manner. For example, the rotatable element  104  may be coupled to the stationary element  106  with a retention element rotatably coupling the rotatable element  104  to the stationary element  106  through an internal passage. Such a retention element is disclosed in, for example, U.S. patent application Ser. No. 15/663,530, filed Jul. 28, 2017, and titled “CUTTING ELEMENT ASSEMBLIES AND DOWNHOLE TOOLS COMPRISING ROTATABLE CUTTING ELEMENTS AND RELATED METHODS,” the disclosure of which is incorporated herein in its entirety by this reference. Other embodiments may include a track with retention pins such as those disclosed in, for example, U.S. patent application Ser. No. 15/662,626, filed Jul. 28, 2017, and titled “ROTATABLE CUTTERS AND ELEMENTS FOR USE ON EARTH-BORING TOOLS IN SUBTERRANEAN BOREHOLES, EARTH-BORING TOOLS INCLUDING SAME, AND RELATED METHODS,” the disclosure of which is incorporated herein in its entirety by this reference. 
     The rotatable element  104  may be configured to move (e.g., float, or slide) relative to the stationary element  106 . The rotatable element  104  may move longitudinally along the longitudinal axis L 100  of the rotatable cutter  100 . In some embodiments, the second interface surface  116  of the stationary element  106  may be configured to limit the longitudinal movement of the rotatable element  104 . For example, when the cutting surface  102  is engaged with an earth formation the rotatable element  104  may be displaced into the stationary element  106  along the longitudinal axis L 100  of the rotatable cutter  100  until the shoulder  112  contacts the second interface surface  116 . 
     In some embodiments, a biasing element  118  (e.g., a motivating element) may be interposed between the stationary element  106  and the rotatable element  104 . The biasing element  118  may be configured to bias the rotatable element  104  in a direction away from the stationary element  106  along the longitudinal axis L 100  of the rotatable cutter  100 . Examples of biasing elements  118  that may be used, by way of example but not limitation, are springs, washers (e.g., Bellville washers), compressible fluids, magnetic biasing, resilient materials, or combinations thereof. In some embodiments, the biasing element  118  may provide a constant force against the base  120  of the rotatable element  104 . For example, when the cutting surface  102  is engaged with an earth formation, there may be an external force exerted on the cutting surface  102  counter to the force of the biasing element  118 . The external force may overcome the biasing element  118  and displace the rotatable element  104  into the stationary element  106  until the shoulder  112  contacts the second interface surface  116 . When the cutting surface  102  is disengaged from the earth formation, the force from the biasing element  118  may move the rotatable element  104  along the longitudinal axis L 100  of the rotatable cutter  100  into a position at least partially spaced from the stationary element  106 . 
     In some embodiments, the rotatable element  104  may rotate about the longitudinal axis L 100  of the rotatable cutter  100 . The rotatable element  104  may freely rotate when the shoulder  112  and the second interface surface  116  are separated. For example, when the cutting surface  102  is disengaged from the earth formation. In some embodiments, the shoulder  112  and the second interface surface  116  may define a frictional and/or mechanical interference engagement feature (e.g., a releasable interface) configured to substantially inhibit rotation of the rotatable element  104  with respect to the stationary element  106  when the shoulder  112  and the second interface surface  116  are placed in at least partial contact. 
     In some embodiments, the engagement feature may include a high friction coating, such as, an abrasive coating (e.g., metal filings, metal oxides, ceramic materials, etc.), a rubberized coating, or other similar high friction coatings. The high friction coating may be applied to at least one of the shoulder  112  or the second interface surface  116 . In some embodiments, the high friction coating may be applied to both the shoulder  112  and the second interface surface  116 . 
     Referring to  FIG. 4 , an exploded view of an embodiment of a rotatable cutter  200  is shown. The rotatable cutter  200  may be similar to rotatable cutter  200  and may include similar features and functionality. For example, rotatable cutter  200  may comprise at least two components, a movable element  204  (e.g., a rotatable element) and a sleeve element  206  (e.g., a stationary element). The movable element  204  may comprise a cutting surface  202  on a first side of a support structure  210  and a first engagement surface  212  (e.g., a shoulder, or a first interface surface) on a second side of the support structure  210 . The cutting surface  202  may be formed from a polycrystalline material, such as, polycrystalline diamond or polycrystalline cubic boron nitride. The support structure  210  of the movable element  204  may be formed from a hard material, such as, for example, a metal, alloy, or ceramic-metal composite. 
     The movable element  204  may be at least partially disposed within the sleeve element  206 . The sleeve element  206  may be formed from a hard material, such as, a metal, alloy, or ceramic-metal composite. The sleeve element  206  may have a second engagement surface  216  (e.g., a second interface surface). The first engagement surface  212  and the second engagement surface  216  may have complementary geometry (e.g., taper, chamfer, or conical shape). 
     In some embodiments, the first engagement surface  212  and the second engagement surface  216  may define an engagement feature (e.g., a frictional and/or interference feature). The engagement feature may comprise opposing patterns configured to interact with each other. For example, the engagement feature may include a pattern of ridges  222 ,  224  (e.g., teeth, protrusions, detents, waves, undulations, zigzag shapes, or combinations thereof) positioned one or more of the first engagement surface  212  and the second engagement surface  216 . The pattern of ridges  222 ,  224  may be configured to at least partially inhibit rotation of the movable element  204  when the first engagement surface  212  contacts the second engagement surface  216 . 
     In some embodiments, the pattern of ridges  222 ,  224  may be positioned on both the first engagement surface  212  and the second engagement surface  216 . The pattern of ridges  222 ,  224  may be configured such that a first pattern of ridges  222  positioned on the first engagement surface  212  is complementary to a second pattern of ridges  224  on the second engagement surface  216 . For example, when the first engagement surface  212  is proximate to the second engagement surface  216  the first pattern of ridges  222  may interlock with the complementary second pattern of ridges  224 . Once interlocked, the first pattern of ridges  222  and the second pattern of ridges  224  may substantially inhibit the rotation of the movable element  204  relative to the sleeve element  206 . 
     In some embodiments, the first pattern of ridges  222  and second pattern of ridges  224  may be configured to enable the movable element  204  to incrementally rotate. The first pattern of ridges  222  and the second pattern of ridges  224  may be configured to interlock at specific intervals. The specific number of the intervals may be defined by a number of ridges  236 ,  230  in the first pattern of ridges  222  and the second pattern of ridges  224 . In some embodiments, the first pattern of ridges  222  may have the same number of ridges  236  as the second pattern of ridges  224 . In other embodiments, the first pattern of ridges  222  may have less than (e.g., half) the number of ridges  236  as compared to the ridges  230  in the second pattern of ridges  224 . In another embodiment, the first pattern of ridges  222  may have more than (e.g., double) the number of ridges  236  as the second pattern of ridges  224 . The number of ridges  230 ,  236 , as well as the angular spacing of the ridges  230 ,  236  may define the increment that the movable element  204  may rotate relative to the sleeve element  206 . 
     In some embodiments, a motivating element  218  (e.g., a biasing element) may be configured to slide the movable element  204  along the longitudinal axis L 200  of the rotatable cutter  200 . The motivating element  218  may act on base  220  of the movable element  204  sliding the movable element  204  away from the sleeve element  206 . In some embodiments, the force of the cutting surface  202  engaging the borehole may slide the movable element  204  until the first engagement surface  212  contacts the second engagement surface  216 . When the cutting surface  202  is disengaged from the borehole the motivating element  218  may introduce a space between the first engagement surface  212  and the second engagement surface  216 . In some embodiments, the space may disengage the first pattern of ridges  222  from the interlocked engagement with the second pattern of ridges  224 . 
     Referring to  FIGS. 5A and 5B , isometric views of the sleeve element  206  and the movable element  204 , respectively, are shown. In some embodiments, the first pattern of ridges  222  located on the first engagement surface  212  may be configured with indexing planes  232  and arresting planes  234  which may define each ridge  236  in the pattern of ridges  222 . The second pattern of ridges  224  located on the second engagement surface  216  may have a complementary configuration. The second pattern of ridges  224  may have complementary indexing planes  226  and complementary arresting planes  228  which may define each complementary ridge  230  in the second pattern of ridges  224 . 
     In some embodiments, the movable element  204  may rotate relative to the sleeve element  206 . The interaction between the first pattern of ridges  222  and the second pattern of ridges  224  may cause the rotation to occur incrementally. For example, when the rotatable cutter  200  engages an earth formation, the movable element  204  may move into the sleeve element  206  along the longitudinal axis L 100  of the rotatable cutter  200  until the first engagement surface  212  rests against the second engagement surface  216 . When the first engagement surface  212  initially contacts the second engagement surface  216 , the indexing planes  232  and the complementary indexing planes  226  may cause the movable element  204  to rotate. The arresting planes  234  and the complementary arresting planes  228  may stop (e.g., arrest, inhibit) the rotation of the movable element  204  when arresting planes  234  and the complementary arresting planes  228  rest against one another. When the rotatable cutter  200  disengages the earth formation, the biasing element  218  ( FIG. 4 ) may move the movable element  204  in a direction out of the sleeve element  206  such that the first engagement surface  212  is no longer in contact with second engagement surface  214 . This movement allows the movable element  204  to move to the next indexing plane  232 ,  226 . The number and spacing of the ridges  230 ,  236  in the second pattern of ridges  224  and the first pattern of ridges  222  may define the incremental rotation of the movable element  204 . 
     Embodiments of rotatable cutter described herein may improve the wear characteristics on the cutting elements of the rotatable cutters. Such rotatable cutters with a feature to at least partially inhibit rotation when the rotatable cutter is under a load may reduce the wear on internal components of the rotatable cutter. Reducing the wear on the internal components may, in turn, reduce the wear on the associated cutting element. 
     Embodiments of the disclosure may be particularly useful in providing a cutting element with improved wear characteristics of a cutting surface that may result in a longer service life for the rotatable cutting elements. Extending the life of the rotatable cutting elements may, in turn, extend the life of the earth-boring tool to which they are attached. Replacing earth-boring tools or tripping out an earth-boring tool to replace worn or damaged cutters is a large expense for downhole earth-boring operations. Often earth-boring tools are on a distal end of a drill string that can be in excess of 40,000 feet long. The entire drill string must be removed from the borehole to replace the earth-boring tool or damaged cutters. Extending the life of the earth-boring tool may result in significant cost savings for the operators of a downhole earth-boring operation. 
     The embodiments of the disclosure described above and illustrated in the accompanying drawing figures do not limit the scope of the invention, since these embodiments are merely examples of embodiments of the invention, which is defined by the appended claims and their legal equivalents. Any equivalent embodiments are intended to be within the scope of this disclosure. Indeed, various modifications of the present disclosure, in addition to those shown and described herein, such as alternative useful combinations of the elements described, may become apparent to those skilled in the art from the description. Such modifications and embodiments are also intended to fall within the scope of the appended claims and their legal equivalents.