Research on mechanical and geometrical characteristics of materials used for flexible tubing production

Coiled tubing used in operational exploitation of oil and gas wells are made of special steels which have to resists to some special requirements such as: tensile strength, internal pressure resistance, collapsing resistance, fatigue strength, corrosion resistance and action of weakening factors. It is interesting that various producers are using different compositions of their steels obtaining quite different mechanical characteristics of the flexible tubing delivered on the market. This paper is presenting the experimental programme for mechanical tests conducted on materials used for production of flexible tubing and the results obtained during these tests. In addition to the materials testing there were studied geometrical characteristics of the flexible tubing such as wall thickness, ovality, cilindricity and their impact on operational life of the flexible tubing.