Device and process for the lining of a pipe branch, particuarly in an oil well

A method for lining and sealing a bifurcation in a well having a main bore and an oblique secondary bore by using a preform in which the angle between a main section and a secondary section of the preform is close to that of the bifurcation, said method comprising:

• a) lowering said preform into the well when in a radially retracted state and with the secondary section pressed against the main section, the combination having a rectilinear configuration;
• b) positioning the preform in the area of the bifurcation so that a free end of the secondary section is at the entry of the oblique bore;
• c) inflating said preform at a moderate pressure so as to rupture progressively restraining bindings and to cause progressive radial unfolding and angular deployment of the secondary section concomitantly with further lowering of the preform;
• d) lowering is stopped when the bifurcate portion of the preform is substantially positioned at the level of the bifurcate portion of the well;
• e) further inflating said preform by increasing its internal pressure to cause it to expand radially and to press it against the walls of the well;
• f) with the increased internal pressure maintained, heating the preform to polymerize the wall;
• g) deflating and separating an expander tool from the preform.