C90 Oil Casing

C90 Oil Casing is a medium strength casing designed for specific corrosive environments in API standards. "C90" represents a minimum yield strength of 90ksi (approximately 621MPa), and its performance is similar to T95 but focuses more on corrosion resistance optimization. It is suitable for medium deep wells and medium pressure oil and gas wells containing corrosive media.

Performance and Material

The C90 casing is made of corrosion-resistant low-alloy steel (such as 13Cr-4Ni, 22Cr duplex steel), which undergoes controlled rolling and tempering heat treatment (850 ℃ controlled rolling+580 ℃ tempering). The yield strength is 621-793MPa, the tensile strength is ≥ 724MPa, the elongation is ≥ 17%, the impact energy is ≥ 32J, and the toughness is slightly lower than T95, but the corrosion resistance is better. Through rigorous HIC (hydrogen induced cracking) and SSC (sulfide stress corrosion) testing, it can adapt to acidic formations with hydrogen sulfide concentration ≤ 1500ppm, with a temperature resistance limit of 140 ℃, and a service life 15% -20% longer than T95 in humid corrosive environments.

Structure and specifications

For seamless steel pipe structure, API standard threads (STC, LTC) are mainly used at the ends, and high-end models are equipped with sulfur resistant special threads (such as VAM ACE), with an airtight sealing pressure of ≥ 38MPa. Common specifications: outer diameter of 114.3mm-219.1mm, wall thickness of 5.87mm-10.16mm, single length of 6-10m, connected to a complete set of pipe columns through couplings, with a weight about 5% lighter than T95 of the same specification.

Manufacturing and Application

The manufacturing process adds a corrosion-resistant treatment step on the basis of T95. The tube blank is subjected to surface passivation treatment after hot rolling and perforation, and coated with special sulfur resistant grease after thread processing. Mainly used for:

Conventional oil and gas wells containing hydrogen sulfide (well depth 2000-3500 meters);

Shallow water oilfield casing string containing carbon dioxide;

Layered isolation of gas and water wells (resistant to chloride ion corrosion in water).