Well Bore Casing Cutting Tool With Expandable Cutter Bases and Having Nose Section Cutting Capability

Abstract

A wellbore casing cutting tool having multiple expandable cutter bases. The leading or downhole ends of the cutter bases are tapered, forming a tapered nose profile, and are covered with hardened cutting material to form a cutting surface. The cutting surface on the tapered nose profile can be used to remove a cement sheath within a casing string being cut or milled.

I claim: 
     
         1 . An apparatus for cutting wellbore casing downhole, comprising:
 a main body comprising a longitudinal bore and a plurality of elongated cutter bases movably attached thereto, said cutter bases attached to said main body by a plurality of positioning arms hingedly connected thereto, said positioning arms being of substantially equal length so that said cutter bases remain substantially parallel to a longitudinal axis of said main body when moved between a first retracted position and a second extended position;   a plurality of cutters attached to an upper section of each of said cutter bases, whereby a lower section of said cutter bases without cutters comprises a stabilizer section;   an operating mechanism for moving said cutter bases from said first retracted position to said second extended position, said operating mechanism comprising a sliding piston disposed in said bore of said main body and movable by fluid flow through said bore of said main body, said piston having an upper section with a diameter closely fitting a diameter of said main body bore and a seal element between said upper section of said piston and said bore, and a lower section with a reduced diameter, said piston positioned so as to engage a heel section of said positioning arms and bear down on same so as to rotate said positioning arms outwardly and move said elongated cutter bases from said first position to said second position, said piston further having a longitudinal bore therethrough;   each of said cutter bases having a tapered nose section on a lower end, said tapered nose section comprising a hardened cutting surface thereon.   
     
     
         2 . The apparatus of  claim 1 , wherein said positioning arms comprise heel sections shaped wherein a fluid path downhole through said main body bore is created when said positioning arms are in an extended position, and wherein said said piston comprises a plurality of angled flow passages such that a portion of fluid flow through said piston bore flows through said fluid path in said positioning arms heel portions, and a portion of fluid flow is angled outwardly onto said positioning arms. 
     
     
         3 . The apparatus of  claim 1 , further comprising a pair of pins disposed in said main body proximal said lower section of said piston within said main body bore, so as to align said lower piston section within said main body bore. 
     
     
         4 . The apparatus of  claim 3 , wherein said cutters are elongated along said cutter bases and positioned such that an upper end of said cutters is inclined in a direction of rotation of said apparatus. 
     
     
         5 . The apparatus of  claim 4 , wherein said cutters comprise carbide covered cutting surfaces. 
     
     
         6 . The apparatus of  claim 4 , wherein said cutters comprise carbide buttons. 
     
     
         7 . The apparatus of  claim 4 , wherein said cutters comprise polycrystalline diamond compact inserts. 
     
     
         8 . The apparatus of  claim 1 , further comprising a jetted sub and a safety joint positioned above said main body. 
     
     
         9 . The apparatus of  claim 1 , wherein said positioning arms and cutter bases are dimensioned so that said positioning arms and said cutter bases, when said cutter bases are in said second extended position, bear against said main body. 
     
     
         10 . An apparatus for cutting wellbore casing downhole, comprising:
 a main body comprising a longitudinal bore and a plurality of elongated cutter bases movably attached thereto, said cutter bases attached to said main body by a plurality of positioning arms hingedly connected thereto, said positioning arms being of substantially equal length so that said cutter bases remain substantially parallel to a longitudinal axis of said main body when moved between a first retracted position and a second extended position;   a plurality of cutters attached to an upper section of each of said cutter bases, whereby a lower section of said cutter bases without cutters comprises a stabilizer section;   a means for moving said cutter bases from said first retracted position to said second extended position, said means comprising a sliding piston disposed in said bore of said main body and movable by fluid flow through said bore of said main body, said piston having an upper section with a diameter closely fitting a diameter of said main body bore and a seal element between said upper section of said piston and said bore, and a lower section with a reduced diameter, said piston positioned so as to engage a heel section of said positioning arms and bear down on same so as to rotate said positioning arms outwardly and move said elongated cutter bases from said first position to said second position, said piston further having a longitudinal bore therethrough;   further comprising a pair of pins disposed in said main body proximal said lower section of said piston within said main body bore, so as to align said lower piston section within said main body bore.   
     
     
         11 . The apparatus of  claim 10 , wherein each of said cutter bases comprises a tapered nose section on a lower end, said tapered nose section comprising a hardened cutting surface thereon. 
     
     
         12 . An apparatus for cutting wellbore casing downhole, comprising:
 a main body comprising a longitudinal bore and a plurality of elongated cutter bases movably attached thereto, said cutter bases attached to said main body by a plurality of positioning arms hingedly connected thereto, said positioning arms comprising gear teeth thereon, said positioning arms being of substantially equal length so that said cutter bases remain substantially parallel to a longitudinal axis of said main body when moved between a first retracted position and a second extended position;   a plurality of cutters attached to an upper section of each of said cutter bases, whereby a lower section of said cutter bases without cutters comprises a stabilizer section;   an operating mechanism for moving said cutter bases from said first retracted position to said second extended position, said operating mechanism comprising a sliding piston disposed in said bore of said main body and movable by fluid flow through said bore of said main body, said piston having an upper section with a diameter closely fitting a diameter of said main body bore and a seal element between said upper section of said piston and said bore, and a lower section with a reduced diameter, said lower section comprising gear teeth thereon, whereby said piston gear teeth engage said positioning arm gear teeth and with longitudinal movement of said piston rotate said positioning arms outwardly and move said elongated cutter bases from said first position to said second position, said piston further having a longitudinal bore therethrough;   each of said cutter bases having a tapered nose section on a lower end, said tapered nose section comprising a hardened cutting surface thereon.   
     
     
         13 . A method of milling a casing string having a cement sheath on an interior wall thereof, comprising the steps of:
 a. milling a window in a desired downhole location in said casing string, leaving an upwardly facing casing edge;   b. providing an apparatus comprising: a main body comprising a longitudinal bore and a plurality of elongated cutter bases movably attached thereto, said cutter bases attached to said main body by a plurality of positioning arms hingedly connected thereto, said positioning arms being of substantially equal length so that said cutter bases remain substantially parallel to a longitudinal axis of said main body when moved between a first retracted position and a second extended position;
 a plurality of cutters attached to an upper section of each of said cutter bases, whereby a lower section of said cutter bases without cutters comprises a stabilizer section; 
 a means for moving said cutter bases from said first retracted position to said second extended position, said means comprising a sliding piston disposed in said bore of said main body and movable by fluid flow through said bore of said main body, said piston having an upper section with a diameter closely fitting a diameter of said main body bore and a seal element between said upper section of said piston and said bore, and a lower section with a reduced diameter, said piston positioned so as to engage a heel section of said positioning arms and bear down on same so as to rotate said positioning arms outwardly and move said elongated cutter bases from said first position to said second position, said piston further having a longitudinal bore therethrough; 
 each of said cutter bases having a tapered nose section on a lower end, said tapered nose section comprising a hardened cutting surface thereon; 
   c. lowering said apparatus downhole on a drillstring and positioning said apparatus so that said cutters are within said window, with said stabilizer section of said cutter bases below said window;   d. pumping fluid down said drillstring so as to move said cutter bases outward so that said stabilizer section of said cutter bases contact said inner wall of said casing;   e. rotating and lowering said apparatus so as to contact said cement sheath with said cutting surfaces on said tapered nose of said cutter bases and remove said cement sheath, and continuing to rotate and lower said apparatus until said cutters contact said upwardly facing casing edge;   f. rotating and lowering said apparatus, while pumping fluid flow through said apparatus, while cutting said casing with said cutters and removing any cement sheath on said inner casing wall with said tapered nose cutting surface.