Abstract: The invention relates to a method of creating a casing in a borehole formed in an underground formation. The method comprises the steps of (a) installing a tubular liner in the borehole, the liner being radially expandable in the borehole whereby the liner in its radially expanded position has a plurality of openings which are overlapping in the longitudinal direction of the liner, (b) radially expanding the liner in the borehole, and (c) either before or after step (b), installing a body of hardenable fluidic sealing material in the borehole so that the sealing material fills said openings and thereby substantially closes said openings. The sealing material is selected so as to harden in said openings and thereby to increase the compressive strength of the liner.