High chrome/nickel milling with PDC cutters

Abstract

A method of downhole milling of an item having high chrome/high nickel content, using polycrystalline diamond cutting elements, exhibiting less wear, requiring less torque and weight, and producing less heat, than prior art tungsten carbide elements.

1 . A method for downhole milling of material having high nickel content or high chrome content, or both, said method comprising: 
 provide a mill body adapted to be attached to a work string, with at least one row of polycrystalline diamond cutting elements mounted adjacent to a peripheral surface of said mill body;    lower said mill body into a well bore;    rotate said mill body in a selected direction about a longitudinal axis of said mill body to mill said material having high nickel content or high chrome content with said polycrystalline diamond cutting elements.    
   
   
       2 . The method recited in  claim 1 , further comprising: 
 provide each said cutting element in said at least one row with a cutting face oriented substantially toward said selected direction of rotation of said mill body, with a major transverse dimension on each said cutting face, said major transverse cutting face dimension being measured substantially transverse to said selected direction of rotation of said mill body; and    space apart adjacent said cutting elements in said at least one row, said spacing being measured substantially along a line parallel to said longitudinal axis of said mill body;    wherein said spacing between any two adjacent cutting elements in said at least one row is at least 20% of said major transverse cutting face dimension on either of said two adjacent cutting elements.    
   
   
       3 . The method recited in  claim 1 , further comprising orienting said at least one row of said cutting elements substantially along a spiral line along the periphery of said mill body.