Method and apparatus for providing protected multilateral junctions

Abstract

A method of providing a protected lateral well junction is disclosed. A milling assembly and whipstock are run into a cased primary wellbore to a desired depth and orientation. An anchor and packer are set. A window is milled in the cased borehole and a lateral rat hole is drilled. The milling assembly is removed, and the window and rat hole are filled with a protecting material, thereby covering any rough or jagged edges of the window. A new hole is drilled in the protecting material, through the window and into the lateral rathole, slightly offset from the window edges that are isolated by the remaining protecting material.

What is claimed is:  
     
         1 . A method of forming a protected multilateral well junction at the intersection of a primary borehole having a casing and a lateral borehole, the method comprising: 
 cutting a window in the casing of the primary borehole;    filling said window with a protecting material; and    drilling the lateral borehole through said window and said protecting material, whereby a portion of said protecting material remains in said window thereby isolating said casing from said lateral borehole.    
     
     
         2 . The method of  claim 1 , further comprising running a tubular into said lateral borehole.  
     
     
         3 . The method of  claim 2 , wherein said tubular is an expandable tubular.  
     
     
         4 . The method of  claim 3 , further comprising expanding said expandable tubular in said lateral borehole.  
     
     
         5 . The method of  claim 1 , further comprising running a screen into said lateral borehole.  
     
     
         6 . The method of  claim 1 , wherein said window has a predetermined width and the lateral borehole has a diameter that is less than said predetermined width.  
     
     
         7 . The method of  claim 1 , wherein said window has a longitudinal length and a substantially uniform width along the longitudinal length.  
     
     
         8 . A method of forming a protected multilateral well junction at the intersection of a primary borehole having a casing and a lateral borehole, the method comprising: 
 lowering a milling assembly releasably connected to a whipstock and plug assembly into the primary borehole;    anchoring the whipstock and plug assembly with the casing at a predetermined position and orientation;    disconnecting the milling assembly from the whipstock and plug assembly;    lowering and rotating the milling assembly having at least one cutting member;    guiding the cutting member towards the casing along a ramp on the whipstock until a window is cut in the casing of the primary borehole;    retrieving the milling assembly from the primary borehole;    inserting a protecting material into the primary borehole and filling said window with said protecting material;    lowering a drilling assembly into said primary borehole;    removing said protecting material from the primary borehole;    guiding the drilling assembly through the window and drilling the lateral borehole through said window and said protecting material, whereby a portion of said protecting material remains in said window thereby isolating said casing from said lateral borehole; and    retrieving said drilling assembly from the primary borehole.    
     
     
         9 . The method of  claim 8 , further comprising running a tubular into said lateral borehole.  
     
     
         10 . The method of  claim 9 , wherein said tubular is an expandable tubular.  
     
     
         11 . The method of  claim 10 , further comprising expanding said expandable tubular in said lateral borehole.  
     
     
         12 . The method of  claim 8 , further comprising running a screen into said lateral borehole.  
     
     
         13 . The method of  claim 8 , further comprising retrieving said whipstock and plug assembly from the primary wellbore.  
     
     
         14 . The method of  claim 8 , wherein said window has a predetermined width and the lateral bore has a diameter that is less than said predetermined width.  
     
     
         15 . The method of  claim 8 , wherein said window has a longitudinal length and a substantially uniform width along the longitudinal length.