The high temperature Tyrihans field required an expandable liner for dual lateral
production wells. The tubing material selected for Tyrihans production wells is alloy UNS S41426
(grade 110ksi). Since the expandable liner is directly exposed to reservoir fluids, the material
needs to meet the same corrosion and environmental cracking performance as the tubing.
The initial program attempted to qualify alloy UNS S41426 (grade 80ksi). Mechanical property
analysis and expansion trials (ID ratio of 19.8%) concluded this alloy to be unsuitable for the
required expansion ratio. Alternative alloys, UNS S31603 and UNS N08904 were selected for
evaluation via expansion trials and environmental cracking tests in simulated Tyrihans well
completion brine and reservoir fluid. 4 Point Bent Beam (4PBB, longitudinal) and C-Ring
(transverse) tests on post-expanded alloys were conducted in high chloride-containing
environments, with and without CO2/H2S. The results proved the suitability of the alloys through
expansion trials, but UNS S31603 revealed susceptibility to corrosion attack if oxygen is
introduced into the system.