Expanding steel tubing with a mandrel having a tapered expansion section and well with such tubing

摘要

A method of expanding an at least partly solid (i.e. unslotted) steel tubing 4, made of a formable steel grade, comprises moving an expansion mandrel 5, having a tapering expansion section, through the tubing thereby plastically expanding the tubing. The tubing is subject to strain hardening without incurring any necking and ductile fracturing. The tapering expansion section of the mandrel has a tapering ceramic outer surface 6. A well provided with the tubing is also claimed, the tubing being expanded according to the above method against the inner surface of a casing inside an underground borehole.