Method and device for casing a bored well portion

Abstract

The invention comprises using a tube having a ductile and radially expansible upper portion, provided at the base thereof with a seal that is also radially expansible under the action of the weight of the tube, the latter being thus sized so that when its base abuts the bottom of the well, the upper portion is located above a fractured area to be isolated, the procedure comprising the following steps: the tube is inserted into the well so that the base thereof bears against the bottom, triggering the radial expansion of the seal; using an expansion tool, the upper portion of the tube is radially expanded beyond its yield strength in order to apply the same tightly against the wall of the well above the fractured area. The invention can be used in the petroleum industry.

1 - 11 . (canceled) 
     
     
         12 . A method for casing a drilled well portion, notably an oil or gas producing well, wherein a cylindrical tube with a slightly smaller diameter than that of the borehole is used, the tube having an upper portion which is ductile and radially expansible, the tube being provided at base thereof with a seal gasket, the seal gasket being expansible under the effect of the tube weight, the tube having a smaller length than that of the drilled well portion, but sufficient so that, when the base bears against a bottom of the drilled well portion, said upper portion is positioned above a fractured area, the method comprising:
 introducing the tube axially into the drilled well portion in such a way that the base bears against the bottom of the drilled well portion and causes radial expansion of the seal gasket, forcing the seal gasket to be applied in a substantially leak-proof way against the well wall which surrounds the seal gasket;   by means of an expander tool, radially expanding the upper portion of the tube beyond a yield strength thereof, so as to apply the upper portion of the tube intimately against the well wall which surrounds the tube, at a level located above the fractured area.   
     
     
         13 . The method of  claim 12 , wherein the step of radially expanding the upper portion of the tube by means of an expander tool includes radially expanding an inflatable bladder with an elastic membrane. 
     
     
         14 . The method of  claim 12 , wherein the step of radially expanding the upper portion of the tube is stepwise. 
     
     
         15 . The method of  claim 12 , wherein the step of radially expanding the upper portion of the tube includes gradually expanding the upper portion of the tube from bottom to top. 
     
     
         16 . The method of  claim 12 , wherein at a beginning of the operation, said expander tool is firmly attached to the tube, and an assembly formed with said expander tool and said tube, is lowered into the well until the tube rests on the bottom of the well, after which the tube is detached therefrom in order to proceed with a radial expansion of the upper portion of the tube. 
     
     
         17 . A device for casing a drilled well portion, notably an oil or gas producing well, comprising:
 a cylindrical tube with a slightly smaller diameter than that of a borehole, at least an upper portion of the tube being ductile and radially expansible, the tube being provided at a base thereof with a seal gasket that is radially expansible under the effect of the tube weight, the tube having a smaller length than that of the drilled well portion, but sufficient so that when the base bears against a bottom of the drilled well portion, said upper portion being positioned above a fractured area; and   an expander tool controlled from the surface and capable of achieving radial expansion of the upper portion of the tube beyond its yield strength, so as to apply the upper portion of the tube intimately against the well wall which surrounds the tube.   
     
     
         18 . The device of  claim 17 , wherein the expander tool and the tube are provided with mating connecting members configured to be coupled with each other in order to form an assembly in which the mating connecting members are separable from each other. 
     
     
         19 . The device of  claim 18 , wherein the mating connecting members of the expander tool and of the tube are screw threads adapted to securely engage each other. 
     
     
         20 . The device of  claim 19 , wherein the expander tool is equipped, at a lower end thereof, with a threaded member capable of being screwed into a tapped ring positioned inside the tube, at the base of said ductile radially expansible upper portion of the tube. 
     
     
         21 . The device of  claim 17 , wherein the seal gasket is a flexible and elastically deformable ring-shaped member, and wherein a lower end portion of the tube includes two telescopic tubular elements between which the seal gasket is interposed, wherein a relative displacement of the tubular elements causes radial expansion of the seal gasket, by a corner effect, when they are brought closer to each other. 
     
     
         22 . The device of  claim 17 , wherein said ductile radially expansible upper portion of the tube is surrounded by at least one ring-shaped seal gasket.