Abstract:
A method of manufacturing a downhole tool includes machining at least one mill blade integral cage comprising a plurality of mill blades arranged around a central axis and securing the at least one mill blade integral cage on a tool body.

Description:
BACKGROUND 
       [0001]    1. Field of the Disclosure 
         [0002]    Embodiments disclosed herein relate generally to downhole tools. In particular, embodiments disclosed herein relate to methods to manufacture downhole tools with finished features as an integral cage. 
         [0003]    2. Background Art 
         [0004]    Traditionally, whipstocks have been used to drill a deviated borehole from an existing earth borehole. The whipstock has a ramp surface which is set in a predetermined position to guide the drill bit on the drillstring in a deviated manner to drill into the side of the earth borehole. In operation, the whipstock is set on the bottom of the existing earth borehole, the set position of the whipstock is surveyed, the whipstock is properly oriented for directing the drillstring in the proper direction, and the drillstring is lower into the well into engagement with the whipstock. This causes the whipstock to orient the drillstring to drill a deviated borehole into the wall of the existing earth borehole. 
         [0005]    Previously drilled and cased wellbores, for one reasons or another, may become unproductive. When a wellbore becomes unusable, a new borehole may be drilled in the vicinity of the existing cased borehole or alternatively, a new borehole may be sidetracked from or near the bottom of a serviceable portion of the cased borehole. Sidetracking from a cased borehole is also useful for developing multiple production zones. Sidetracking is often preferred because drilling, casing, and cementing the borehole are avoided. This drilling procedure is generally accomplished by either milling out an entire section of pipe casing followed by drilling through the side of the now exposed borehole, or by milling through the side of the casing with a mill that is guided by a wedge or “whipstock” component. 
         [0006]    Current milling tool used for sidetracking operations generally include a tool body having mill blades attached to the tool body and arranged around a circumference thereof. Current manufacturing processes typically include multiple individual steps, including cutting individual mill blades, welding the mill blades to the tool body, and finish machining the mill blades to specific blade geometry. Cumulatively, the individual steps may extend the manufacturing process unnecessarily and increase costs. In addition, the multiple manufacturing steps may be conducive to the inability to maintain proper tolerances of the mill blade features. 
         [0007]    Accordingly, there exists a need for a method of consolidating the manufacturing steps required for milling tools used in sidetracking. 
       SUMMARY OF THE DISCLOSURE 
       [0008]    In one aspect, embodiments disclosed herein relate to a method of manufacturing a downhole tool, the method including machining at least one mill blade integral cage comprising a plurality of mill blades arranged around a central axis and securing the at least one mill blade integral cage on a tool body. 
         [0009]    In other aspects, embodiments disclosed herein relate to a milling tool including a tool body and at least one mill blade integral cage disposed on the tool body and comprising a plurality of mill blades arranged around a central axis, wherein the at least one mill blade integral cage is configured to be machined as a separate single component prior to being assembled onto the tool body. 
         [0010]    Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  shows a perspective view of a milling tool in accordance with one or more embodiments of the present disclosure. 
           [0012]      FIGS. 2A-2C  show perspective and end views of a lead mill blade integral cage in accordance with one or more embodiments of the present disclosure. 
           [0013]      FIGS. 3A-3B  show perspective views of a follow mill blade integral cage in accordance with one or more embodiments of the present disclosure. 
           [0014]      FIGS. 4A-4B  show method steps during assembly of the milling tool in accordance with one or more embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    In one aspect, embodiments disclosed herein relate to methods of manufacturing a milling tool, including machining mill blade integral cages and assembling the mill blade integral cages on a tool body of the milling tool. 
         [0016]    Referring to  FIG. 1 , a perspective view of a milling tool  100  in accordance with one or more embodiments of the present disclosure is shown. Milling tool  100  includes a tool body  102  having a main head  104  disposed on a distal end thereof, “lead” mill blades  110  disposed slightly up an axial length of the tool body  102  from the main head  104 , and “follow” mill blades  120  disposed further up an axial length of the tool body  102  from the lead mill blades  110 . In accordance with embodiments disclosed herein, the lead mill blades  110  and follow mill blades  120  may be manufactured as integral components prior to assembly onto the tool body  102 . 
         [0017]    Now referring to  FIGS. 2A-2C , perspective and end views of a lead mill blade integral cage  110  in accordance with one or more embodiments of the present disclosure are shown. As shown in  FIG. 2B , the lead mill blade integral cage  110  may be machined from tubing  50  ( FIG. 2A ). In certain embodiments, the tubing may be a low carbon steel, for example, including, but not limited to, AISI 1018-1026. The finish machined integral cage  110  may include individual longitudinally formed mill blades  112  having cutting edges (not shown) formed thereon. As shown, the mill blades  112  may be configured having a slight helix along a longitudinal length of the blades. In addition, the integral cage  110  may include tabs or end rings  114  dispersed circumferentially therebetween at either end. Alternatively, the tabs  114  may form a continuous ring about a circumference at either end of the mill blade integral cage  110 . An inner diameter of the finish machined integral cage  110  may be slightly larger than an outer diameter of tool body  102  such that the integral cage  110  just slides over the tool body  102 . In certain embodiments, the inner diameter of the finish machined integral cage  100  may be between about 0.010 and 0.020 inches larger than the outer diameter of the tool body  102 . 
         [0018]    Referring to  FIGS. 3A-3B , perspective views of a follow mill blade integral cage  120  in accordance with one or more embodiments of the present disclosure are shown. The follow mill blade integral cage  120  may be machined from tubing  52  ( FIG. 3A ) and include individual longitudinally formed mill blades  122  having cutting edges formed thereon (not shown). As previously described, the tubing  52  may be a low carbon steel, for example, including, but not limited to, AISI 1018-1026. As shown, the mill blades  122  may be configured having a slight helix along a longitudinal length of the blades. In addition, the integral cage  120  may include tabs or end rings  124  dispersed circumferentially therebetween configured to provide support. In addition, an inner diameter of the finish machined integral cage  120  may be slightly larger than an outer diameter of the tool body  102  such that the integral cage  120  just slides over the tool body  102 . 
         [0019]    Methods of manufacturing the milling tool in accordance with one or more embodiments of the present disclosure are described in reference to  FIGS. 4A-4B . Initially, the tool body  102  of the milling tool  100  may be machined to a specified profile and diameter. For instance, in certain embodiments, a shoulder  103  may be machined in a profile of the tool body  102  where a diameter of the tool body  102  transition to a smaller diameter for the lead mill blade integral cage  110 . The shoulder  103  may also be configured to serve as a stop to limit an axial length of the tool body  102  onto which the mill blade integral cage  110  may be installed. Next, the integral cages (i.e., the lead mill blades integral cage  110  and the follow mill blade integral cage  120 ) may be machined from tubing as a single component. In certain embodiments, a computer numerical control (“CNC”) programming may be used to machine the integral cages  110 ,  120 , as will be understood by those skilled in the art. Once machined, the integral cages  110 ,  120  may be assembled onto the tool body  102  by sliding the integral cages  110 ,  120  into the tool body  102 , as shown. 
         [0020]    The integral cages  110 ,  120  may be rotated as needed to properly align the integral cages on the tool body. Alignment may refer to an axial alignment (i.e., a certain distance from a bottom end of the tool body  102 ) and a circumferential alignment (i.e., mill blades orientation as to a left or right hand helix). Once the integral cages  110 ,  120  are assembled and properly aligned onto the tool body  102 , the integral cages and tool body  102  may be preheated and welded to secure the integral cages to the tool body. In certain embodiments, preheat temperatures may be within a range of about 800 degrees Fahrenheit and 1000 degrees Fahrenheit. Any suitable method of welding may be used as known to those skilled in the art. In alternate embodiments, the integral cages  110 ,  120  may be secured to the tool body  102  using mechanical fasteners or other methods known to those skilled in the art. After the integral cages  110 ,  120  are secured on the tool body  102 , a carbide outer coating or other type of cladding may be applied on surfaces of the integral cages, particularly the weldment and the body area between the mill blades to provide a protective barrier against copper infiltration into the tool body. 
         [0021]    Further, the outer surfaces of the mill blades may be dressed with a crushed carbide matrix to create an aggressive cutting profile. Generally the crushed carbide matrix includes a metal cutting grade of carbide crushed to sizes up to ⅜ inch and suspended in a nickel-based matrix. In certain embodiments, a product that is commercially available and known as Kutrite®, available from B&amp;W Metals located in Houston, Tex., may be used. In alternate embodiments, the mill blades may be dressed with cylindrical inserts (made from either steel cutting grade of carbide or PDC) by having holes drilled in the mill blades and inserts brazed in the holes such that the arrangement creates an aggressive cutting profile. Finally, outer surfaces of the integral cages  110 ,  120  may be ground to smooth any imperfections in weld beads or otherwise. 
         [0022]    Advantageously, embodiments of the present disclosure provide more cost effective and faster methods of assembling a milling tool. In particular, methods in accordance with embodiments disclosed herein include fewer manufacturing steps, which increases production and reduces overall manufacturing costs. In certain instances, methods of assembly in accordance with embodiments disclosed herein have reduced manufacturing times by half. In particular, the number of heating/cooling phases previously required may be reduced, which allows improved controlled pre-heat, post-heat, and cool down per certain engineering specifications. The improved heating/cooling control may minimize blade failure (e.g., cracking) due to hot working processes. Further, because the mill blade integral cages are manufactured prior to assembly onto the tool body, more precise geometries may be achieved for the individual mill blades, which may lead to more consistent performance and a reduction in product failures during use. Still further, because the mill blade integral cages are installed as a single unit, they may easily be removed and replaced if required. 
         [0023]    While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. Accordingly, the scope of the disclosure should be limited only by the attached claims.