Downhole tubing

Abstract

A downhole apparatus comprises a plurality of tubing sections. Each tubing section has substantially cylindrical end portions initially of a first diameter for coupling to end portions of adjacent tubing sections. The end portions are expandable to a larger second diameter. Each tubing section also has an intermediate folded wall portions initially in a folded configuration. The intermediate folded wall portions are unfoldable to define a substantially cylindrical form of a third diameter.

We claim:  
     
         1 . Downhole apparatus comprising a plurality of tubing sections, each tubing section having: substantially cylindrical end portions initially of a first diameter adapted for coupling to end portions of adjacent tubing sections and said end portions being expandable at least to a larger second diameter; and intermediate folded wall portions initially in a folded configuration and being unfoldable to define a substantially cylindrical form of a third diameter.  
     
     
         2 . The apparatus of  claim 1 , wherein transition portions are provided between the end portions and the intermediate portions of each tubing section, and said transition portions are deformable by a combination of both unfolding and expansion.  
     
     
         3 . The apparatus of  claim 1 , wherein the end portions are threaded.  
     
     
         4 . The apparatus of  claim 1 , wherein the first diameter is smaller than the third diameter.  
     
     
         5 . The apparatus of  claim 1 , wherein the second and third diameters are substantially the same.  
     
     
         6 . The apparatus of  claim 1 , wherein the unfolded intermediate wall portion is expandable from the third diameter to a larger fourth diameter.  
     
     
         7 . The apparatus of  claim 6 , wherein the fourth diameter is substantially the same as the second diameter.  
     
     
         8 . A method of lining a bore comprising the steps: 
 providing a plurality of tubing sections, each tubing section having substantially cylindrical end portions of a first diameter and an intermediate folded wall portion in a folded configuration;    coupling the tubing sections together via the end portions to form a tubing string;    running the tubing string into a bore; and    reconfiguring the tubing string by expanding the end portions at least to a larger second diameter and unfolding the intermediate folded wall portions to define a substantially cylindrical form of a third diameter.    
     
     
         9 . The method of  claim 8 , further comprising reconfiguring transition portions between the end portions and the intermediate portions by a combination of both unfolding and expansion.  
     
     
         10 . The method of  claim 8 , comprising threading the tubing sections together.  
     
     
         11 . The method of  claim 8 , wherein the first diameter is smaller than the third diameter.  
     
     
         12 . The method of  claim 8 , wherein the second and third diameters are substantially the same.  
     
     
         13 . The method of  claim 8 , further comprising the step of expanding the unfolded intermediate wall portions from the third diameter to a larger fourth diameter.  
     
     
         14 . The method of  claim 13 , wherein the fourth diameter is substantially the same as the second diameter.  
     
     
         15 . The method of  claim 8 , wherein at least one of the unfolding and expansion steps is achieved by rolling expansion utilising a rotating body carrying one or more rolling members.  
     
     
         16 . The method of  claim 15 , wherein both the unfolding and expansion steps are achieved by rolling expansion.  
     
     
         17 . The method of  claim 15 , wherein the unfolding step is achieved by rotation and axial advancement of a set of rolling members arranged in a conical form.  
     
     
         18 . The method of  claim 15 , wherein the expansion step is achieved by a set of rolling members arranged to be urged radially outwardly into contact with the tubing section wall.  
     
     
         19 . The method of  claim 8 , wherein the unfolding step is achieved by bending of the tubing wall.  
     
     
         20 . The method of  claim 8 , wherein the expansion step is achieved by radial deformation of the wall, reducing the wall thickness and thus increasing the wall diameter.