Casing mill, method, and system

Abstract

A mill for a single casing string including a housing, a first blade section having a blade of a first profile disposed in the housing and positionable to axially mill the single casing string, a second blade section having a blade of a second profile disposed in the housing and positionable to axially mill the single casing string, the first and second blades deployable simultaneously, the second blade configured to ride on an inside diameter surface of the single casing string while the second blade in the deployed position.

What is claimed is: 
     
         1 . A mill for a single casing string comprising:
 a housing;   a first blade section having a blade of a first profile disposed in the housing and positionable to axially mill the single casing string;   a second blade section having a blade of a second profile disposed in the housing and positionable to axially mill the single casing string, the first and second blades deployable simultaneously, the second blade configured to ride on an inside diameter surface of the single casing string while the second blade in the deployed position.   
     
     
         2 . The mill as claimed in  claim 1  wherein at least one of the first blade section and the second blade section includes a plurality of blades. 
     
     
         3 . The mill as claimed in  claim 1  wherein the housing is a first housing supporting the first blade and a second housing supporting the second blade, the first and second housings being connected to one another to create a fluid pathway to both the first and second housings whereby both first and second blade are actuable by the same hydraulic pressure event. 
     
     
         4 . The mill as claimed in  claim 1  wherein the first and second blade are rotated in the deployed position simultaneously. 
     
     
         5 . The mill as claimed in  claim 1  wherein the first blade is configured to mill radially and axially. 
     
     
         6 . The mill as claimed in  claim 1  wherein the second blade during use is restrained from full radial deployment only by the inside diameter surface of the casing string in which the mill is run. 
     
     
         7 . A method for milling a single casing string comprising:
 rotating a mill having a first blade and a second blade, wherein both the first blade and the second blade are rotating and deployed;   axially milling the casing string with the first blade; and   contacting an inside diameter surface of the casing with the second blade without milling through the casing with the second blade.   
     
     
         8 . The method as claimed in  claim 7  wherein the rotating the first blade includes opening a window in the casing. 
     
     
         9 . The method as claimed in  claim 7  wherein the axial milling with the first blade is continued until the first blade is worn. 
     
     
         10 . The method as claimed in  claim 8  wherein the second blade automatically extends radially outwardly when it reaches the window. 
     
     
         11 . The method as claimed in  claim 7  wherein the second blade axially mills the casing after the first blade is worn to extend the window longitudinal length. 
     
     
         12 . A wellbore system comprising:
 a borehole in a subsurface formation;   a string in the borehole; and   a mill as claimed in  claim 1  disposed in or as a part of the string.