The difference between the J55 and N80 casing and tubing

The API 5CT standard covers seamless and welded casing and tubing pipes for oil and gas transportation.Casing pipes are available in the following materials: H-40, J-55, K-55, N-80, L-80, C-90,T-95 ,P-110, Q-125.

Depending on the different condition and the depth of the well,we should use the different steel grades.The corrosion resistance of the casing is also required under the corrosive environment. In the case of complex geological conditions, the casing has to be resistant to collapse.Most casing steel grades are largely of the same chemical composition. What gives each grade its distinct properties is the kind of heat treatment applied. Casing grades mainly differ in their yield strength, tensile strength, and hardness.

• J55: A commonly used grade for most wells when it meets the design criteria. Some operators recommend it be full-length normalized or normalized and tempered after upsetting when used in carbon dioxide or sour service (ring-worm corrosion problems); however, such heat treatments increase costs. J55 has been the "standard" grade for tubing in most relatively shallow (< 9,000 ft) and low-pressure (< 4,000 psi) wells on land. 
• N80: A relatively old grade with essentially open chemical requirements. It is susceptible to H 2 S-induced SSC (acronym). It is acceptable for sweet oil and gas wells when it meets design conditions. The quenched-and-tempered heat treatment is preferred. The N80 grade is normally less expensive than L80 grades. 

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