Abstract:
A downhole cutting tool includes, a body, a first contoured cutting element in operable communication with the body, and at least one contingency contoured cutting element in operable communication with the first contoured cutting element and the body. A contour of the at least one contingency contoured cutting element substantially matches a contour of the first contoured cutting element, and the at least one contingency contoured cutting element is maintainable in reserve and positioned to substitute for the first contoured cutting element if the first contoured cutting element becomes detached.

Description:
BACKGROUND 
       [0001]    Downhole cutting tools commonly employ carbide cutters made of a solid piece of carbide. Although such cutters are effective at cutting the downhole materials they are designed to cut, their cutting efficiency, and effective lifespan, can be significantly reduced due to fracturing or chipping of the cutter. Fracturing and chipping can remove all or a portion of a cutting edge of the carbide cutter resulting in a dull and inefficient cutting tool. Well operators will therefore be receptive to tools and methods to increase the longevity of downhole cutters. 
       BRIEF DESCRIPTION 
       [0002]    Disclosed herein is a downhole cutting tool. The tool includes, a body, a first contoured cutting element in operable communication with the body, and at least one contingency contoured cutting element in operable communication with the first contoured cutting element and the body. And a contour of the at least one contingency contoured cutting element substantially matching a contour of the first contoured cutting element, the at least one contingency contoured cutting element being maintainable in reserve and positioned to substitute for the first contoured cutting element if the first contoured cutting element becomes detached. 
         [0003]    Further disclosed herein is a method of making a downhole cutter. The method includes, substantially matching a contoured cutting edge of at least one contingency contoured cutting element with a contoured cutting edge of a first contoured cutting element, and attaching the at least one contingency contoured cutting element adjacent the first contoured cutting element such that the at least one contingency contoured cutting element substitutes for the first contoured cutting element if the first contoured cutting element becomes detached. 
         [0004]    Further disclosed herein is a downhole cutter. The cutter includes, a plurality of cutting elements having substantially matched contoured cutting edges, and a bonding material having greater ductility than the plurality of cutting elements bonding the plurality of cutting elements to one another in an arrangement such that detachment of one of the plurality of cutting elements reveals another of the substantially matched contoured cutting edges that substitutes for a contoured cutting edge of the detached cutting element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0006]      FIG. 1  depicts a perspective view of a downhole cutting tool disclosed herein; 
           [0007]      FIG. 2  depicts an enlarged perspective view of a portion of the downhole cutting tool of  FIG. 1 ; and 
           [0008]      FIG. 3  depicts an enlarged perspective view of a plurality of carbide cutting elements shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0010]    Referring to  FIG. 1 , an embodiment of a downhole cutting tool  10  having a plurality of cutters  12  disclosed herein is illustrated. The tool  10  is just one embodiment of the invention to facilitate illustration of a break away construction of the cutter  12  that leaves a new cutting edge as will be disclosed in detail hereunder. In addition to the cutters  12 , the cutting tool  10  includes, a tubular  14  and a plurality of articulatable bodies  18 , also commonly referred to as arms or shanks. Each of the cutters  12  includes a plurality of contoured cutting elements  22 A- 22 D attached thereto. The cutting tool  10  is positionable in a downhole wellbore via a drill string (not shown), for example, where it can be used to cut metal, earth or other materials whose removal is desired. The tool  10  can also be used to cut windows in walls of a wellbore, for example, to create a lateral wellbore from a primary wellbore. The plurality of contoured cutting elements  22 A- 22 D are configured on the cutter  12  to break away from the cutter  12  in full elements  22 A- 22 D, thereby limiting the extend of a fracture to a single element  22 A- 22 D. In so doing, each time an element  22 A- 22 C breaks free from the tool  10 , a new (contingent) element  22 B- 22 D becomes exposed with a new cutting edge that substitutes for the cutting edge of the detached element  22 A- 22 C. 
         [0011]    In this particular embodiment, the bodies  18  can articulate from a position wherein the cutters  12  are positioned radially inwardly of a diameter  26  that defines the tubular  14 , to a position wherein the cutters  12  (during rotation of the cutting tool  10 ) trace out a diameter  30  that is substantially larger than the diameter  26 . It should be noted that alternate embodiments of the cutting tool  10  could have fixed bodies  18  as well. A characteristic of any embodiment of the cutting tool  10  is that the tool  10  can move in such a way as to force the cutter  12  and cutting elements  22 A- 22 D, attached to the body  18 , to contact and thereby cut into a material intended to be removed. 
         [0012]    Referring to  FIGS. 2 and 3 , the body  18 , cutter  12  and contoured cutting elements  22 A- 22 D are shown at greater magnification. This embodiment includes three stacks  34  of the contoured cutting elements  22 A- 22 D that are attached at a distal end  38  of the body  18 . Alternate embodiments could have a single stack  34  or more than three stacks  34 . A first contoured element  22 A in one of the stacks  34  has an exposed edge  46 A that defines a first cutting contour  50 A. The additional elements  22 B,  22 C and  22 D, in any particular stack  34 , have cutting contours  50 B- 50 D that substantially match the first cutting contour  50 A. The first cutting contour  50 A can be formed to any desired shape practical by such methods as wire EDM, cutting with a diamond saw or by sintering, for example. Each of the elements  22 A- 22 D are brazed, bonded, glued or welded to one another or to the body  18  with a bonding material  54 . 
         [0013]    Regardless of the bonding method used, the elements  22 A- 22 D disclosed herein are made of a hard metal material such as tungsten carbide, titanium carbide or tantalum carbide, for example, or other hard material such as a ceramic (cubic boron nitride) or diamond. In embodiments disclosed herein the elements  22 A- 22 D are made of tungsten carbide, also referred to as carbide. Carbide has exceptional hardness, a high melting point, and excellent wear characteristics when used as a cutting tool for cutting metal and earth formation materials. The elements  22 A- 22 D, by design, are harder and more brittle than the bonding materials  54  employed and than the material of the body  18 , which is made of a strong rigid material such as steel, for example. With the foregoing construction the more ductile bonding materials  54  and the body  18  will absorb much of the shock incurred while cutting. Should a load incurred be so great as to cause detachment of a portion of the cutter  12  the bonding material  54  should fail prior to fracture of one of the elements  22 A- 22 D, thereby limiting the loss of a piece of the cutter  12  to that of an individual element  22 A- 22 D. The foregoing construction thereby limits the loss of carbide volume from the cutter  12  due to each excessive load in comparison to a single solid piece cutter  12 , for example. Additionally, should a fracture of an element  22 A- 22 D occur the ductile bonding material  54  would prevent the fracture from propagating to an adjacent element  22 A- 22 D, again limiting the size of a fracture chip to the size of an individual element  22 A- 22 D. 
         [0014]    Further, when, for example, the first element  22 A of a stack  34  is detached at a bonding interface the contingent element  22 B becomes exposed. And since the contingent element  22 B has a contour  50 B that substantially matches the contour  50 A of the first element  22 A, the contingent element  22 B is positioned to substitute for and continue cutting of the target material. This substitution effect is possible because the first element  22 A is displaced from the contingent element  22 B in a direction according to arrow  58  ( FIG. 1 ), defined by motion of the cutter  12  while cutting. Also, since the contour  50 B of the contingent element  22 B matches that of the first element  22 A the desired original cutting profile can be maintained. A newly exposed contoured cutting edge  46 B on element  22 B having been formed in a similar fashion as the first contoured cutting edge  46 A will be just as well suited for cutting and will be more durable and less susceptible to fracture than an edge randomly formed from a chip broken from a cutter  12  made of a single solid piece of carbide, for example. 
         [0015]    Since each of the stacks  34  can have multiple contingent elements  22 B- 22 D, with three contingent elements  22 B- 22 D being illustrated in this embodiment, a new cutting edge  46 B- 46 D can be reestablished several times without having to retrieve the tool  10 . 
         [0016]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.