Abstract:
A reamer bit for use in earth boring operations comprising a body, cutter mounts having rolling cutters on the bit body, and stabilizers pads on the body placed between adjacent cutter mounts. The reamer may further include a pilot bit on a drill pipe extending downward from the reamer body. The reamer bit outer periphery with its stabilizers and bit body has a radial profile approximating a circle thereby reducing dynamic perturbations during drilling operations.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 61/016,209, filed Dec. 21, 2007, the full disclosure of which is hereby incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    This disclosure relates to earth boring reamer bits, and particularly to reamer bits having stabilizers disposed on the bit body. 
         [0004]    2. Description of Prior Art 
         [0005]    Drill bits used in drilling of subterranean well bores typically comprise drag bits and roller cone bits. Roller cone bits typically comprise a body having legs extending downward and a head bearing extending from the leg towards the axis of the bit body. Frusto-conically shaped roller cones are rotatably mounted on each of these journals and are included with cutting teeth on the outer surface of these cones. As the bit rotates, the cones rotate to cause the cutting elements to disintegrate the earth formation. 
         [0006]    In some situations a pilot reamer drilling system is employed where two or more bits are combined on a single drill string at different vertical positions. The lower bit of the pilot reamer drilling system, which is commonly referred to as a pilot bit, creates a pilot hole. The upper bit, which follows the lower bit in the drilling process, enlarges the hole diameter over that created by the pilot bit. The bit enlarging the hole diameter is referred to as a reamer bit. Typically the pilot bit comprises a conventional earth boring bit, i.e. either a roller cone bit or a drag bit. The reamer bit usually employs roller cone bits as cutting members modified for attachment to the reamer bit body. Pilot reamer drilling systems are used for drilling large diameter wellbores or surface holes which require enhanced stabilization. 
       SUMMARY OF INVENTION 
       [0007]    The disclosure herein includes a reamer bit for downhole earth boring operations comprising, a reamer body having an axis, rolling cutters mounted on the body, and stabilizers disposed between adjacent cutters. Pockets may be provided on the body outer diameter formed to receive the stabilizers and cutter mounts therein. A pilot bit is affixed to the drill shaft extending from the body&#39;s lower end. The pilot bit can be a roller cone bit or a drag bit. An updrill surface may be included formed on the upper portion of the cutter mounts and the stabilizer pads. The combined radial profile of the bit legs and the stabilizer pads can approximate a circular shape. 
         [0008]    In an alternative embodiment, the present disclosure includes a pilot reamer apparatus for earth boring use comprising a reamer body having an upper end and a lower end, an axis extending through the upper and lower ends, an outer periphery circumscribing the axis, and pockets formed in the outer periphery, a drill string attachment on the body upper end, a drill pipe segment on the body lower end, a pilot bit affixed to the drill pipe terminal end, cutter mounts on the body outer periphery extending downwardly, rolling cutters rotatingly affixed to the mounts, and stabilizer pads affixed to the reamer body outer periphery disposed between adjacent bit legs. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]    Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
           [0010]      FIG. 1  is a side view of a reamer bit body with rolling cutters and stabilizer pads. 
           [0011]      FIG. 2  is a perspective view of a reamer bit with attached pilot bit. 
           [0012]      FIG. 3  is an upward looking view of a reamer bit in accordance with the present disclosure having stabilizers. 
       
    
    
       [0013]    While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF INVENTION 
       [0014]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
         [0015]    It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims. 
         [0016]      FIG. 1  provides in a side view an example of a reamer  20  comprising a generally cylindrical body  22  having cutter mounts  24  and stabilizer pads  28  affixed on its outer lateral periphery. The stabilizer pads  28  are disposed between adjacently located cutter mounts  24 . In the embodiment shown, the cutter mounts  24  and the stabilizer pads  28  are elongate members wherein their lengthwise axes are substantially aligned with the axis A of the bit body  22 . Each cutter mount  24  comprises a bearing shaft (not shown) extending from the outer end of the mount  24  in a generally downward direction in towards the axis A. Cutters  26  are rotatably mounted on each shaft and have rows of inserts or teeth  27  formed in a generally circumferential arrangement on the cutters outer surface. The inserts  27  also referred to as cutting elements may be secured to the cutter shell in apertures of selected dimensions, integrally formed, such as by machining (teeth), or later attached after forming the cutter  26  and affixed by welding and/or brazing. 
         [0017]    The reamer  20  further includes a connector  34  on its upper end, wherein the connector is generally concentrically placed around the axis A of the cylindrical body  22 . The connector  34  includes threads (not shown) for connection to an associated drill string. A shaft  36  is shown at the bottom end of cylindrical body  22  and extends downward for attachment of a pilot drill bit. Pockets  30  may be formed on the lateral periphery of the body  22  configured to receive cutter mounts  24  and stabilizer pads  28 . The bit legs and stabilizer pads  28  may be welded or brazed to the body  22 . Furthermore, hard facing  32  may be included on the outer surface of the stabilizer pads  28 . Additionally, the upper portion of the stabilizer pads  28  and cutter mounts  24  may be included with ridges inserts, or other raised elements for providing an updrilling function when drawing the reamer  20  upward within the well bore. 
         [0018]      FIG. 2  provides a perspective view of the reamer  20  combined with the shaft  36  and a pilot bit  38  fixed to the lower terminal end of the shaft  36  thereby forming a pilot reamer assembly  18 . The assembly  18  may be attachable to the lower end of a drill string (not shown) and attached thereto by the connector  34 . While the pilot bit  38  is illustrated as a drag bit, it may also comprise a roller cone bit. The pilot reamer system  18  of  FIG. 2  may be used to drill large diameter boreholes in which conventional drill bits are less stable due to the radial distance between adjacent cutters. 
         [0019]      FIG. 3  is an upward-looking view of a bottom of a reamer  20  embodiment. In this view the stabilizer pads  28  extend downward between adjacently positioned cutters  26  of corresponding mounts  24 . The stabilizer pads  28  enhance reamer  20  outer circumference surface continuity by providing additional borehole diameter contact points on the reamer outer surface. Enhancing the reamer  20  outer circumference surface continuity aligns the bit in the wellbore and limits the lateral displacements and distributes the side loads more evenly when a cutter  26  tangentially strikes the wellbore wall. Thus better alignment promotes rotation about the center of the reamer and prevents dynamic dysfunctions such as bit whirl. 
         [0020]    To help maintain a continuity of surface, the stabilizer pads in one embodiment may have an outer profile or curvature substantially the same as the outer profile of the cutter mounts. The result of this can be seen in  FIGS. 2 and 3  wherein the reamer  20  has a generally circular configuration due to the presence of the stabilizers  28 . The circular configuration is also attributed to the pad outer surface having large diameter curvature and the stabilizer pads  28  having an outer radial profile similar to the cutter mounts  24  outer radial profile. This similarity in outer radial approximates a full circle, thus limiting open spaces that may produce lateral displacements and high side forces during reaming operations. 
         [0021]    The stabilizer pads  28  can have any shape or configuration suitable for smoothing bit operations and total contact area. This includes an elongate member where the elongate axis is parallel to the body axis, perpendicular to the body axis, or oblique to the body axis. Moreover, the reamer  20  profile having stabilizer pads  28  is not limited to a substantially circular shape, but can be any shape, such as one having multiple sides where a side is defined as the area between each adjacent stabilizer pad  28  and cutter mount  24 .