Sealed multilateral junction system

Abstract

A sealed multilateral junction system provides fluid isolation between intersecting wellbores in a subterranean well. In a described embodiment, a method of forming a wellbore junction includes the steps of sealing a tubular string in a branch wellbore to a tubular structure in a parent wellbore. The tubular string may be secured to the tubular structure utilizing a flange which is larger in size than a window formed in the tubular structure. The flange may be sealed to the tubular structure about the window by a metal to metal seal or by adhering the flange to the tubular structure.

1 - 49 . (canceled)  
   
   
       50 . A method of forming a wellbore junction in a subterranean well, the method comprising the steps of: 
 drilling a first wellbore;    installing a casing string in the first wellbore;    drilling a second wellbore extending outwardly from the first wellbore;    aligning a window formed through a sidewall of the casing string with the second wellbore;    positioning a member within the casing string;    forming an opening through a sidewall of the member, the opening having projections extending into the opening;    folding the projections outward into the window; and    then installing a liner string through the opening and into the second wellbore.    
   
   
       51 . The method according to  claim 50 , wherein the opening forming step is performed before the member positioning step, and wherein the positioning step further comprises aligning the opening with the window.  
   
   
       52 . The method according to  claim 50 , wherein the opening forming step is performed after the member positioning step.  
   
   
       53 . The method according to  claim 50 , further comprising the step of expanding the member within the casing string.  
   
   
       54 . The method according to  claim 53 , wherein the member expanding step is performed after the member positioning step.  
   
   
       55 . The method according to  claim 53 , wherein the member expanding step is performed before the folding step.  
   
   
       56 . The method according to  claim 53 , wherein the expanding step further comprises sealing between the member and the casing string.  
   
   
       57 . The method according to  claim 56 , wherein the sealing step further comprises forming a metal to metal seal between the member and the casing string.  
   
   
       58 . The method according to  claim 56 , wherein the sealing step further comprises providing a sealing material between the member and the casing string.  
   
   
       59 . The method according to  claim 53 , wherein the casing string includes a tubular structure having the window formed therein, and wherein the expanding step further comprises expanding the member within the tubular structure.  
   
   
       60 . The method according to  claim 59 , wherein the expanding step further comprises expanding the member into a radially enlarged portion of the tubular structure, so that an internal dimension of the member is greater than or equal to a minimum internal diameter of the casing string above the window.  
   
   
       61 . The method according to  claim 59 , wherein the expanding step further comprises sealing between the member and the tubular structure.  
   
   
       62 . The method according to  claim 61 , wherein the sealing step further comprises forming a metal to metal seal between the member and the tubular structure.  
   
   
       63 . The method according to  claim 61 , wherein the sealing step further comprises providing a sealing material between the member and the tubular structure.  
   
   
       64 . The method according to  claim 50 , wherein in the liner string installing step, the liner string has an outer diameter greater an inner dimension of the opening, the liner string thereby enlarging the opening as the liner string passes through the opening.  
   
   
       65 . The method according to  claim 64 , wherein the enlarging step further comprises sealing between the liner string and the member in the opening.  
   
   
       66 . The method according to  claim 65 , wherein the sealing step further comprises forming a metal to metal seal between the liner string and the member about the opening.  
   
   
       67 . The method according to  claim 65 , wherein the sealing step further comprises providing a sealing material between the liner string and the member in the opening.  
   
   
       68 . The method according to  claim 65 , wherein the sealing step further comprises isolating an interior of the casing string from the first and second wellbores external to the casing string.  
   
   
       69 . The method according to  claim 50 , further comprising the step of cutting off an upper end portion of the liner string extending inwardly through the opening, after the step of installing the liner string.