Abstract
High strength, high collapse resistance carbon steel casing materials are required in many deep water High Pressure High Temperature wells. However, the high strength limits the ability of steels to be qualified in a mildly sour environment. This paper describes a novel fit for purpose and multi-disciplinary approach to evaluate and qualify these materials in these environments while considering worst case loading and exposure conditions. The methodology addresses the uncertainty in sour gas estimations, comes up with evaluation criteria based on worst case discharge and well design principles and uses engineering critical assessment (fracture mechanics) and associated inspection acceptance criteria to qualify high strength, high collapse carbon steel materials. The methodology relies on extensive inputs from well designers, production chemists and geochemists, metallurgists and corrosion and inspection experts.
