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BACKGROUND 
       [0001]    1. Field of Invention 
         [0002]    The invention is directed to downhole milling tools utilized in oil and gas wells to abrade, cut, or mill an object within the well and, in particular, to downhole cutting tools having a blade that is retracted during run-in and extended radially outward for cutting, abrading, or milling. 
         [0003]    2. Description of Art 
         [0004]    In the drilling, completion, and workover of oil and gas wells, it is common to perform work downhole in the wellbore with a tool that has some sort of cutting profile interfacing with a downhole structure. Examples would be milling a downhole metal object with a milling tool or cutting through a tubular with a cutting or milling tool. To facilitate these operations, cutting elements are disposed on the downhole cutting tool. In one type of milling tool, the cutting elements are disposed on blades that can be disposed in a retracted position and an extended position. In certain of these embodiments, the blades are extended by increasing the pressure across the tool. Upon reduction of the pressure, such as after the milling operation has been completed, the blades are moved back to their retracted position so that the tool can be retrieved from the well. 
       SUMMARY OF INVENTION 
       [0005]    Broadly, the invention is directed to cutting, abrading, or milling tools used to cut or abrade an object within a wellbore. The cutting tool includes at least one cutting blade having a retracted position and a plurality of extended positions. The blade is operatively associated with a sleeve that includes a profile disposed on its outer wall surface. Another profile is disposed on an inner wall surface of the cutting blade such that when the sleeve is moved in a certain direction, the engagement of the two profiles causes the cutting blade to move radially outward so that it can engage and cut the object within the well, or the well itself. The term “object” encompasses any physical structure that may be disposed within a well, for example, another tool that is stuck within the well, a bridge plug, the well tubing, the well casing, the well formation, or the like. 
         [0006]    In one particular embodiment, the tool comprises a mandrel having a bore disposed therein and the sleeve is a piston in sliding engagement with the outer wall surface of the mandrel. Disposed around the periphery of the outer wall surface of the piston is a profile for receiving a profile on a cutting blade. The profile on the piston and the profile on the cutting blade are operatively associated with each other such that movement of the piston in a certain direction will force the cutting blade to move radially outward from the longitudinal axis of the tool. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]      FIG. 1  is a cross-sectional view of one specific embodiment of a downhole cutting tool disclosed herein shown in its run-in position. 
           [0008]      FIG. 2  is cross-sectional view of the downhole cutting tool of  FIG. 1  shown in an extended position. 
           [0009]      FIG. 3  is a partial perspective view of the downhole cutting tool of  FIG. 1  shown in its run-in position. 
           [0010]      FIG. 4  is a partial exploded perspective view of the downhole cutting tool of  FIG. 1 . 
           [0011]      FIG. 5  is a cross-sectional view of the piston of the downhole cutting tool of  FIG. 1 . 
           [0012]      FIG. 6  is a cross-sectional view of a blade of the downhole cutting tool of  FIG. 1 . 
       
    
    
       [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 these embodiments. 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]    Referring now to  FIGS. 1-6 , downhole cutting tool  10  comprises mandrel  20  having upper end  22 , lower end  24 , and bore  26  disposed longitudinally therein. Mandrel  20  is adapted at upper end  22  to be connected to drill or work string (not shown) such as through threads (not shown). Mandrel  20  includes outer wall surface  28 , longitudinal axis  29 , shoulder  30  for supporting cutting blade  70  when tool  10  is in the run-in position ( FIG. 1 ), and ports  32  disposed through outer wall surface  28  and in fluid communication with bore  26 . In the embodiment of  FIGS. 1-6 , outer wall surface  28  also includes lower shoulder  34 . 
         [0015]    Secured to outer wall surface  28  of mandrel  20  is upper gage ring  40  and lower gage ring  42 . Upper gage ring  40  and lower gage ring  42  can be secured to mandrel  20  through any method or device know in the art, such as threads (not shown). Upper gage ring  40  and lower gage ring  42 , when disposed on outer wall surface  28  of mandrel  20 , provide housing  33  within which piston  50  and in which the cutting blade  70  is fully disposed during run-in ( FIG. 1 ) and partially disposed during cutting operations ( FIG. 2 ). 
         [0016]    Piston  50  is in sliding engagement with outer wall surface  28  of mandrel  20  and inner wall surface  44  of lower gage ring. Seals  52  are disposed on piston  50  to reduce the likelihood of leakage occurring between piston  50  and inner wall surface  44  of lower gage ring  42  and between piston  50  and outer wall surface  28  of mandrel  20 . In the embodiment shown in FIGS.  1 - 6 , piston  50  is a sleeve piston and includes a piston shoulder  54  disposed on an inner wall surface  56  of piston  50 . Piston shoulder  54  and inner wall surface  56  of piston  50  are shown best in  FIG. 5 . Piston shoulder  54  facilitates formation of chamber  58  by outer wall surface  28  of mandrel  20 , inner wall surface  56  of piston  50 , and lower shoulder  34  disposed on outer wall surface  28  of mandrel  20 . 
         [0017]    As shown in  FIG. 4 , inner wall surface  56  of piston includes one or more longitudinal piston slots  57  which are capable of receiving torque key  59  disposed on outer wall surface  28  of mandrel  20  to facilitate rotation of piston  50  and, thus, rotation of cutting blades  70 . 
         [0018]    As illustrated in  FIGS. 1-2 , piston  50  is disposed relative to lower gage  42  to provide chamber  60  formed by inner wall surface  44  of lower gage ring  42 , piston  50 , and outer wall surface  28  of mandrel  20 . Chamber  60  is in fluid communication with ports  32 , which are in fluid communication with bore  26 . 
         [0019]    Tool  10  can include a single cutting blade  70 , or a plurality of cutting blades  70 . In one particular embodiment, tool  10  includes two cutting blades. In another specific embodiment, tool  10  includes three cutting blades. In still another embodiment, tool  10  includes four cutting blades. In other embodiments, tool  10  can include five or more cutting blades. 
         [0020]    In addition, in embodiments having multiple cutting blades  70 , the cutting blades  70  may be disposed at any interval around piston  50  that is desired or necessary to provide suitable cutting capability. In one embodiment, each cutting blade  70  is disposed at a regular interval around piston  50 , e.g., two cutting blades  70  can be disposed at 180 degree intervals from one another, three cutting blades  70  can be disposed at 120 degree intervals from one another, four cutting blades  70  can be disposed at 90 degree intervals from one another, five cutting blades  70  can be disposed at 72 degree intervals from one another, six cutting blades  70  can be disposed at 60 degree intervals from one another, and the like. In other embodiments, each cutting blade  70  is disposed at irregular intervals around piston  50 , e.g., two cutting blades  70  can be disposed at a 120 degree interval in one direction and a 240 degree interval in another direction. 
         [0021]    Although not completely shown in  FIGS. 1-6 , tool  10  of  FIGS. 1-6  includes four cutting blades  70  disposed at 90 degree intervals from each other. Due to the views of the Figures, one of the cutting blades cannot be seen and, in  FIGS. 3-4  one of the cutting blades has been removed to better illustrate the piston profile associated with that cutting blade. 
         [0022]    Regardless of the number or location of the cutting blade(s), each cutting blade  70  comprises one or more cutting surfaces. As shown in the embodiments of  FIGS. 1-6 , each cutting blade  70  includes cutting surfaces  71 ,  72 ,  73  upon which cutting elements (not shown) can be secured. Cutting elements are known in the art and include carbide buttons, hardfacing, and any other material known in the art used to facilitate cutting or abrading. 
         [0023]    Piston  50  is operatively associated with one or more cutting blades  70  so that cutting blades  70  are disposed within housing  33  during run-in of the tool  10 , as shown in  FIG. 1 , and so that cutting blades  70  are moved radially outward from the longitudinal axis of tool  10  when piston  50  is moved upward (to the left in the Figures) as shown in  FIG. 2 . In the particular embodiment shown in  FIGS. 1-6 , piston  50  and cutting blades  70  are operatively associated with each other through piston profile  80  and cutting blade profile  90 . As shown in  FIGS. 1-6 , piston profile  80  comprises multiple cam ramps  82  and cam support walls  84  defining angles  85 ,  86 ,  87  and cutting blade profile  90  is reciprocally-shaped with piston profile  80  comprising multiple cam ramps  92  and cam support walls  94  defining angles  95 ,  96 ,  97 . In this embodiment, cutting blade  90  is moved radially outward by sliding piston  50  upward (toward the left in  FIGS. 1-2 ) causing cutting blade cam ramps  92  to slide along piston cam ramps  82  until cutting blades  70  are disposed outside housing  33 . In this position (shown in  FIG. 2 ), cutting blades  70  can cut, abrade, or mill an object disposed within the well (not shown). Thereafter, piston  50  can be moved downward (toward the right in  FIGS. 1-2 ), causing cutting blade cam ramps  92  to slide along piston cam ramps  82  until cutting blades  70  are moved back within housing  33 . 
         [0024]    Although five piston cam ramps  82  and five cutting blade cam ramps  92  are shown in the embodiment of  FIGS. 1-6 , it is to be understood that more or less piston cam ramps  82  and more or less blade cam ramps  92  may be included. In addition, although each of the piston cam ramps  82  are shown in  FIGS. 1-6  to be identical in shape to each other, and identical in shape to each of the cutting blade cam ramps  92 , it is to be understood that each of piston cam ramps  82  may have different shapes, e.g., each of angles  85 ,  86 , and  87  may be different among each of piston cam ramps  82 . Similarly, each of cutting blade cam ramps  92  may have different shapes, e.g., each of angles  95 ,  96 , and  97  may be different among each of cutting blade cam ramps  92 . 
         [0025]    In one particular embodiment, all of piston cam ramps  82  are identical to each other, all of cutting blade cam ramps  92  are identical to each other, angles  85  are in the range from 0 degrees to 90 degrees, angles  86  are in the range from 0 degrees to 90 degrees, angles  87  are in the range from 0 degrees to 90 degrees, angles  95  are in the range from 0 degrees to 90 degrees, angles  96  are in the range from 0 degrees to 90 degrees, and angles  97  are in the range from 15 degrees to 90 degrees. In another specific embodiment, all of piston cam ramps  82  are identical to each other, all of cutting blade cam ramps  92  are identical to each other, angles  85  are each approximately 90 degrees, angles  86  are each approximately 60 degrees, angles  87  are each approximately 60 degrees, angles  95  are each approximately 90 degrees, angles  96  are each approximately 60 degrees, and angles  97  are each approximately 60 degrees. 
         [0026]    In addition, in the embodiment shown in  FIGS. 1-6 , piston profile  80  is disposed in a recess or longitudinal groove  81  disposed on outer wall surface  51  of piston  50 . Groove  81  provides side walls  88 ,  89  that provide support to cutting blades  70  during their extension and engagement with an object or objects to be cut within the well. 
         [0027]    In one specific embodiment, the piston profile  80  and cutting blade profile  90  provide support for the majority of the length, i.e., over 50% of the length, of the cutting blade  70  when in its extended positions, e.g., the position shown in  FIG. 2 . 
         [0028]    In operation, tool  10  is secured to a work string (not shown) and is run-in to the wellbore to the desired depth. During run-in, tool  10  is disposed in the position shown in  FIG. 1 , i.e., the run-in position. Upon reaching the desired location in the wellbore, fluid, such as hydraulic fluid, is pumped down the work string and into bore  26  of tool  10 . The fluid flow through ports  32  into chamber  60  causing an increase in pressure within chamber  60  which acts on lower end  55  of piston  50  to force piston  50  upward, i.e., toward the left in  FIGS. 1-2 . As a result of piston  50  moving upward, cutting blades  70  are moved radially outward to engage an object disposed in the well (not shown) due to the camming action of piston profile  80  acting on cutting blade profile  90 . In the particular embodiment of  FIGS. 1-6 , the camming action is caused by cutting blade cam ramps  92  sliding along piston cam ramps  82  to the position shown in  FIG. 2 . Upon being extended, cutting blade  70  is supported along its longitudinal length by piston profile  80  and by side walls  88 ,  89  of groove  81  to facilitate cutting of the object. 
         [0029]    After extension of cutting blades  70 , the work string (not shown) is rotated. Rotation of the work string results in torque keys  59  rotating piston  50  and, therefore, cutting blades  70 . Rotation of cutting blades  70  results in the object within the wellbore being cut or abraded. In embodiments in which cutting blades  70  have cutting surfaces  72  and  73 , rotation in either direction, i.e., clockwise or counterclockwise, results in cutting or abrasion of the object. In addition, the presence of cutting surface  71  can also facilitate cutting or abrasion of the object regardless of which direction tool  10  is rotated. 
         [0030]    Upon completion of the cutting or abrasion of the object, fluid pressure within bore  26  of tool  10  is reduced. As result, piston  50  is returned to toward its run-in position ( FIG. 1 ) by a force acting on piston  50 . The force acting on piston  50  to return piston  50  toward its run-in position may be due to one or more of hydrostatic pressure within the wellbore acting on piston  50 , atmospheric pressure within chamber  58  acting on piston  50 , resistance of the wellbore formation, wellbore casing, or object being cut acting on cutting blades  70 , which in turn acts on piston  50 , and/or the inclusion of a return member such as a spring (not shown) disposed above lower end  53  of piston  50 . 
         [0031]    In moving piston  50  toward the run-in position, cutting blades  70  are retracted into housing  33 . Upon being returned to the run-in position, tool  10  can be moved within wellbore to remove tool  10  from the wellbore or to move tool  10  to another location for continued cutting and abrasion by repeating the steps described above. 
         [0032]    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. For example, piston profile and cutting blade profile are not required to be reciprocally-shaped as shown in the embodiment of  FIGS. 1-6 . To the contrary, piston profile and cutting blade profile only need to be able to engage one another so that the cutting blade can be extended and retracted. Further, the cross-sectional shape of the cutting blades is not critical. In addition, modification of the angles  85 ,  86 ,  87 ,  95 ,  96 ,  97 , as well as the height of support walls  84  and  94  can be done to provide the desired or necessary extension and support of the cutting blades. Moreover, to the extent that the terms well or wellbore are argued to be limiting in their definition, it is to be understood that these terms should not be limited and these terms as used herein include, but are not limited to, cased wellbores, open-hole wellbores cut into a formation, and boreholes. Additionally, the terms cutting, milling, abrading are to be understood has having coextensive definitions. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.

Summary:
Downhole cutting tools comprise a mandrel, a housing, a sleeve and a cutting blade. The mandrel comprises an inner wall surface defining a bore, and an outer wall surface. The housing is secured to the outer wall surface of the mandrel and comprises an opening. The sleeve is engaged with the outer wall surface of the mandrel. The sleeve comprises a profile that is operatively associated with a profile of the cutting blade such that movement of the sleeve causes the profile of the piston to slide along the profile of the cutting blade. In so doing, the cutting blade is radially extended outward through the opening in the housing to abrade an object located outside the housing. Movement of the sleeve can be achieved by pumping fluid down a bore in the mandrel to slide the sleeve long the outer wall surface of the mandrel.