Wellbore Casing Cutting Tool

Abstract

A wellbore casing cutting tool, having multiple blades which rotate outwardly by a fluid operated mechanism, has multiple cutters on each blade. The cutters are preferably positioned on the blades such that the lowermost cutting edges of multiple cutters all bear on the surface of the casing being cut. The cutters are preferably made with a metal base, covered with hardened cutting material such as tungsten carbide or hardened cutting buttons. The metal wears away as cutting progresses, continually exposing fresh cutting surfaces. The multiple cutters permit cutting of long windows in casing walls, and the structure of the cutters results in relatively short metal cuttings, rather than long metal cuttings which can ball up downhole.

I claim: 
     
         1 . A well bore casing cutting tool, comprising:
 a main body having a longitudinal axis therethrough and comprising a means for connecting said cutting tool to a drillstring;   a plurality of blades rotatably attached to said main body, and rotatable between a first, retracted position and a second, extended position in which said blades are extended outwardly from said main body, said plurality of blades disposed about a circumference of said main body;   a means for rotating said plurality of blades between said first and second positions; and   one or more cutters on each of said plurality of blades, wherein each of said one or more cutters has an elongated cross section shape, with a longer dimension of said shape angled in a direction of desired rotation of said cutting tool and with respect to said longitudinal axis of said main body, each of said cutters comprising a hardened cutting surface.   
     
     
         2 . The cutting tool of  claim 1 , wherein each of said blades comprises two or more of said cutters. 
     
     
         3 . The cutting tool of  claim 1 , wherein each of said blades comprises three or more of said cutters. 
     
     
         4 . The cutting tool of  claim 1 , wherein said hardened cutting surface of each of said cutters comprises a tungsten carbide coating. 
     
     
         5 . The cutting tool of  claim 1 , wherein said hardened cutting surface of each of said cutters comprises a plurality of hardened cutting buttons. 
     
     
         6 . The cutting tool of  claim 1 , wherein each of said cutters is inclined with respect to said longitudinal axis of said main body of said tool by an angle of between 7 degrees and 10 degrees. 
     
     
         7 . The cutting tool of  claim 6 , wherein said cutters comprise a metal base softer than a casing string being cut, and a plurality of hardened cutting buttons affixed to said metal base. 
     
     
         8 . The cutting tool of  claim 7 , wherein a lower edge of said cutters is angled downward in a direction away from said main body of said cutting tool. 
     
     
         9 . A well bore casing cutting tool, comprising:
 a main body having a longitudinal axis therethrough and comprising a means for attachment to a drillstring;   a plurality of blades rotatably attached to said main body, and rotatable between a first, retracted position and a second, extended position in which said blades are extended outwardly from said main body, said plurality of blades disposed about a circumference of said main body;   a means for rotating said plurality of blades between said first and second positions; and   a first row of two or more cutters on each of said plurality of blades, wherein each of said two or more cutters has an elongated generally rectangular cross section shape, with a longer dimension of said shape inclined in a direction of desired rotation of said cutting tool and at an angle to said longitudinal axis of said main body, each of said cutters comprising a metal base and a hardened cutting surface comprising a plurality of hardened cutting buttons affixed to a face of said cutters.   
     
     
         10 . The cutting tool of  claim 9 , wherein said cutters are integrally formed with said blades. 
     
     
         11 . The cutting tool of  claim 9 , wherein said buttons comprise a polygon cross section shape. 
     
     
         12 . The cutting tool of  claim 11 , wherein said buttons comprise a concave face. 
     
     
         13 . The cutting tool of  claim 11 , wherein said buttons comprise a face having a plurality of dimples therein. 
     
     
         14 . The cutting tool of  claim 11 , wherein said hardened cutting buttons comprise tungsten carbide. 
     
     
         15 . The cutting tool of  claim 11 , wherein said hardened cutting buttons comprise polycrystalline diamond compact buttons. 
     
     
         16 . The cutting tool of  claim 11 , wherein a lower edge of said cutters is angled downward in a direction away from said main body of said cutting tool. 
     
     
         17 . The cutting tool of  claim 10 , wherein said buttons comprise a polygon cross section shape. 
     
     
         18 . The cutting tool of  claim 17 , wherein said buttons comprise a concave face. 
     
     
         19 . The cutting tool of  claim 17 , wherein said buttons comprise a face having a plurality of dimples therein. 
     
     
         20 . The cutting tool of  claim 17 , wherein said hardened cutting buttons comprise tungsten carbide. 
     
     
         21 . The cutting tool of  claim 17 , wherein said hardened cutting buttons comprise polycrystalline diamond compact buttons. 
     
     
         22 . The cutting tool of  claim 17 , wherein a lower edge of said cutters is angled downward in a direction away from said main body of said cutting tool. 
     
     
         23 . The cutting tool of  claim 11 , further comprising a second row of two or more cutters on each of said plurality of blades, wherein each of said two or more cutters of said second row has an elongated generally rectangular cross section shape, with a longer dimension of said shape inclined in a direction opposite to said first row of said cutters and at an angle to said longitudinal axis of said main body, each of said second row of cutters comprising a metal base and a hardened cutting surface comprising a plurality of hardened cutting buttons affixed to a face of said cutters, whereby said second row of cutters is disposed to cut a casing surface positioned uphole of said second row of cutters.