Expandable liner for oversized base casing

Abstract

An expandable tubular member comprises a first portion having a first inner diameter and a first wall thickness. A second portion of the expandable tubular member has an increased inner diameter and an increased wall thickness. A transition portion of the expandable tubular member is defined by a wall thickness that varies non-linearly between the first wall thickness and the increased wall thickness.

What is claimed is: 
     
         1 . An expandable tubular member comprising:
 a first portion having a first inner diameter and a first wall thickness;   a second portion having an increased inner diameter and an increased wall thickness; and   a transition portion defined by a wall thickness that varies non-linearly between the first wall thickness and the increased wall thickness.   
     
     
         2 . The expandable tubular member of  claim 1 , wherein the transition portion includes a first length over which the wall thickness remains constant and the inner diameter increases and a second length over which the wall thickness increases and the inner diameter remains constant. 
     
     
         3 . The expandable tubular member of  claim 2 , wherein the wall thickness in the first length of the transition portion is substantially equal to the first wall thickness. 
     
     
         4 . The expandable tubular member of  claim 2 , wherein the inner diameter of the second length of the transition portion is substantially equal to the inner diameter of the increased wall thickness portion. 
     
     
         5 . The expandable tubular member of  claim 1 , wherein the transition portion has either an inner surface or an outer surface defined by at least one radius. 
     
     
         6 . The expandable tubular member of  claim 1 , wherein the transition portion has an outer surface at least partially defined by an outer taper. 
     
     
         7 . The expandable tubular member of  claim 6 , wherein the transition portion has an inner surface at least partially defined by an inner taper that is substantially equal to the outer taper. 
     
     
         8 . The expandable tubular member of  claim 6 , wherein the transition portion has an inner surface having a length that is substantially parallel to the outer surface. 
     
     
         9 . An expandable tubular member comprising:
 a first portion having a first inner diameter and a first wall thickness;   a second portion having an increased inner diameter and an increased wall thickness; and   a transition portion having a first end coupled to the first portion and a second end coupled to the second portion, wherein the transition portion has a wall thickness that increases in a non-linear fashion from the first wall thickness at the first end to the second wall thickness at the second end.   
     
     
         10 . The expandable tubular member of  claim 9 , wherein the transition portion includes a first length over which the wall thickness remains constant and the inner diameter increases and a second length over which the wall thickness increases and the inner diameter remains constant. 
     
     
         11 . The expandable tubular member of  claim 10 , wherein the wall thickness in the first length of the transition portion is substantially equal to the first wall thickness. 
     
     
         12 . The expandable tubular member of  claim 10 , wherein the inner diameter of the second length of the transition portion is substantially equal to the inner diameter of the increased wall thickness portion. 
     
     
         13 . The expandable tubular member of  claim 9 , wherein the transition portion has either an inner surface or an outer surface defined by at least one radius. 
     
     
         14 . The expandable tubular member of  claim 9 , wherein the transition portion has an outer surface at least partially defined by an outer taper. 
     
     
         15 . The expandable tubular member of  claim 14 , wherein the transition portion has an inner surface at least partially defined by an inner taper that is substantially equal to the outer taper. 
     
     
         16 . The expandable tubular member of  claim 14 , wherein the transition portion has an inner surface having a length that is substantially parallel to the outer surface. 
     
     
         17 . A method for expanding a tubular member comprising:
 disposing a tubular member in a wellbore, wherein the tubular member includes a first portion having a first inner diameter and a first wall thickness, a second portion having an increased inner diameter and an increased wall thickness, and a transition portion defined by a wall thickness that varies non-linearly between the first wall thickness and the increased wall thickness;   displacing an expansion cone longitudinally through the tubular member to generate an expansion force that radially expands the tubular member, wherein the expansion force needed to radially expand the transition portion is less than the expansion force needed to radially expand the first portion.   
     
     
         18 . The method of  claim 17 , wherein the transition portion includes a first length over which the wall thickness remains constant and the inner diameter increases and a second length over which the wall thickness increases and the inner diameter remains constant. 
     
     
         19 . The method of  claim 17 , wherein the transition portion has an outer surface at least partially defined by an outer taper. 
     
     
         20 . The method of  claim 19 , wherein the transition portion has an inner surface at least partially defined by an inner taper that is substantially equal to the outer taper.