Single-pass milling assembly

Abstract

The disclosed embodiments include a single-pass milling assembly for use in multilateral systems. In one embodiment, a first operational mode may be used to create a controlled window in a wellbore casing and a second operational mode may be used to begin a lateral wellbore through the controlled window. In certain embodiments, the first operational mode may convert hydraulic energy from a fluid flow to mechanical energy (e.g., using an agitator and power section) to push and rotate a radial mill to create the controlled window. The second operational mode may rotate a drill string to cause an axial mill to mill a rathole through the controlled window. The assembly may create the controlled window and begin the lateral wellbore using only one trip in the wellbore, leaving downhole a fixed deflection tool to provide support for another process that may continue to drill the lateral wellbore.

What is claimed is: 
     
         1 . A method comprising:
 introducing an assembly into a first wellbore, wherein said assembly comprises a deflection tool;   using a first operational mode of said assembly to create a controlled window in a casing of said first wellbore;   fixing said deflection tool in said first wellbore; and   using a second operational mode of said assembly to begin a second wellbore through said controlled window.   
     
     
         2 . The method of  claim 1 , wherein using said second operational mode further comprises rotating a drill string coupled to said assembly. 
     
     
         3 . The method of  claim 2 , wherein using said first operational mode further comprises causing a fluid to flow through said drill string and into said assembly. 
     
     
         4 . The method of  claim 3 , wherein using said first operational mode further comprises converting hydraulic energy from said fluid to rotational force. 
     
     
         5 . The method of  claim 1 , further comprising decoupling said drill string from said deflection tool 
     
     
         6 . The method of  claim 5 , wherein said deflection tool is a whipstock. 
     
     
         7 . The method of  claim 1 , further comprising repositioning said deflection tool in said first wellbore between using said first operational mode and using said second operational mode. 
     
     
         8 . A system comprising:
 an axial mill coupled to a radial mill, in which said system is operable:
 (1) in a first operational mode, in which said radial mill creates a controlled window in a casing of a first wellbore; and 
 (2) in a second operational mode, in which said axial mill begins a second wellbore through said controlled window. 
   
     
     
         9 . The system of  claim 8 , wherein said second operational mode comprises rotating a drill string coupled to said axial mill. 
     
     
         10 . The system of  claim 9 , wherein said first operational mode further comprises rotating said radial mill using a differential pressure. 
     
     
         11 . The system of  claim 10 , wherein said first operational mode further comprises creating said differential pressure by causing a fluid to flow through a drill string coupled to said radial mill. 
     
     
         12 . The system of  claim 11 , wherein said first operational mode further comprises converting hydraulic energy of said fluid to a rotational force. 
     
     
         13 . A system comprising:
 a drill string coupled to an axial mill;   a whipstock coupled to said drill string;   a rotating string disposed within said whipstock; and   a radial mill coupled to said rotating string.   
     
     
         14 . The system of  claim 13 , wherein said rotating string further comprises a power section. 
     
     
         15 . The system of  claim 14 , wherein said rotating string further comprises an agitator. 
     
     
         16 . The system of  claim 15 , wherein said rotating string is coupled to a displaceable string. 
     
     
         17 . The system of  claim 16 , wherein one or more fluid seals are disposed in an annulus between said displaceable string and said whipstock. 
     
     
         18 . The system of  claim 13 , wherein said rotating string further comprises a float valve. 
     
     
         19 . The system of  claim 13 , wherein said radial mill is coupled to said rotating string via a transmission. 
     
     
         20 . The system of  claim 13 , wherein said radial mill is coupled to said transmission via a bearing section.