Offshore platforms are huge steel and concrete structures used for the exploration and extraction of oil and gas from the earth’s crust.
Photo courtesy of Corus
These platforms can weigh over 1 million tonnes and, as they can stand in up to 2 km depth of water and project up to 50 m above sea level, they are among the tallest manmade structures on earth. While some are situated within sight of the shore, they are often many kilometers from land.
Offshore platforms may be fixed or tethered to the seabed, the latter floating. A single platform may be connected to, and therefore take oil and gas from, many wellheads in its vicinity. The oil and gas are separated at the platform and transported through a pipeline or by tanker to shore.
Offshore platforms have many different designs, depending on their location and geological conditions. They have to be carefully designed and fabricated to withstand extremely hazardous conditions – high winds, hurricanes, sub-zero temperatures, icebergs, high currents and tidal forces, the risk of fire and explosion, corrosion and fatigue.
Many types of steel are used in their construction and in the associated pipelines, including carbon, microalloyed, alloy and stainless steels. The fabrication process for an offshore platform involves extensive welding. High strength steel plate is used for the decking and tubular support structure.
In this module you will design such a high strength steel plate for an offshore oil platform. You will be guided through making decisions about the composition and rolling procedures/ heat treatment necessary to produce the steel profitably. Your steel must satisfy the specified mechanical properties and meet the customer’s weldability requirements.
Learning Outcomes for this Section
After completing this section, you should be able to:
- Select a composition and process route suitable for a weldable, high strength plate application on an offshore platform, by applying your knowledge of metallurgical strengthening mechanisms
Pre-Requisites
Before starting, it is important that you are familiar with the following terms: Welding (External site); Hot rolling (External site); Heat treatment (External site);
You should be familiar with the concepts covered in:
References
- Gladman, T, The Physical Metallurgy of Microalloyed Steels, Institute of Materials, 0 901716 81 2
- Llewellyn, DT & Hudd, RC, Steels, Metallurgy and Applications, Butterworths-Heinemann,
- Mintz, B, Ironmaking & Steelmaking, Institute of Materials, Minerals and Mining,
- Mintz, B et al., Mater. Sci. & Tech, ,
- Mintz, B et al., Mater. Sci. & Tech, ,
Authors/Contributors:
- Robert Cochrane, Consultant