The unique attributes of nickel-containing materials make their use in the oil and gas sector a sound engineering and cost-effective investment, even at today’s high initial costs. Deep wells need tubing that is highly resistant to corrosion. For example, nickel-containing stainless steels, such as S31803, can be cold-worked to 965 MegaPascals yield strength and still retain high toughness and resistance to corrosion. (Photo 1)
Precipitation hardenable nickel alloys, such as N07718 and N09925, can be heat treated to form precipitates in the matrix of the alloy which impart strength and hardness to the material. “Down-hole jewelry” (a generic term for all the special tools that are incorporated into an oil or gas well) has complex shapes that require precipitation-hardened nickel alloys to achieve exceptional strength without developing sensitivity to hydrogen embrittlement. (Photo 2)
Nickel alloy (typically N06625)-clad well heads and so-called “Christmas trees” (assemblies of valves, spools and fittings for oil wells) also combine excellent weldability and compatibility with steel substrates. They provide cost-effective corrosion resistance wherever needed. (Photo 3)
Carbon steel (in comparison with clad and lined pipe) has to be protected from corrosion by the injection of corrosion inhibiting chemicals. Nickel alloy N08825 and stainless steel-clad and -lined pipelines solve the problem of transporting wet corrosive oil and gas without requiring inhibitor injection to prevent corrosion. (Photo 4)
Vessels made of 9Ni steel (containing 9% nickel) are a cost-effective option for liquefied natural gas storage vessels with an excellent track record of safe service. That’s because 9Ni steel has high toughness at cryogenic temperatures. (Photo 5)
Internally weld overlay or cladding with nickel alloy N06625 provide long-term protection of vessels from corrosion without the need for frequent inspection and replacement of organic coatings. These pressure vessels are used to separate different phases in fluids or to carry out chemical reactions. (Photo 6)
Heat exchangers are used to move heat from one medium to another. Usually in oil and gas plants, the problem is trying to cool down the oil and gas. Oil, for example, must be cooled from between 200 and 90°C down to 25°C before it can be transported to customers. Stainless steel and nickel alloy (N10276) heat exchangers provide the optimum solution to the demands for heat transfer and long-term resistance to corrosion in equipment that is virtually impossible to protect by inhibitor injection. (Photo 7)
Austenitic stainless steel piping and valves in low temperature sections of plant are essential for achieving reliable toughness down to cryogenic conditions. This is necessary because liquefied natural gas is transported at minus 164°C.
The choice of a low-expansion alloy with 36% nickel elliminates thermal stress problems in pipelines and hoses carrying liquefied natural gas.
As mentioned above, in the case of carbon steel piping, a chemical has to be injected to stop corrosion. That chemical ends up in the fluid that is re-injected back into the ground. Corrosion-resistant nickel-containing stainless steel and nickel alloys on the other hand help to minimize the risk of contamination of the surroundings or ground waters due to spillage of corrosion inhibitor-contaminated water.
Nickel alloys are also the safe choice for the development of oil and gas reserves that contain hydrogen sulphide. In many cases, these development projects are in remote parts of the world and are therefore automated to the extent that they operate largely without personnel. Nickel alloys provide the reliability that is essential for these types of projects.
Where engineering requirements are demanding, nickel-containing materials are the proven solution. They provide life-long integrity with the potential for re-use in other projects, and their high intrinsic value is such that recycling is cost-effective and well-established.
Photos: Butting - Bimetallrohre and Nickel Institute
From Nickel Magazine, Dec. 2007.