What is the difference between J55, K55, N80-1, N80Q, and P110 of commonly used oilfield API-5CT casing steel grades?

Commonly used oilfield API-5CT casing steel grades are J55, K55, N80-1, N80Q, P110. Casings are mostly used in oil well drilling. According to the API-5CT standard, pipes can be divided into STC (short thread), LTC (long thread) and BTC (support thread) and their joints.

Oilfield casing is placed in the wellbore and held in place to prevent subterranean formation and wellbore collapse and also to allow drilling mud to circulate and be extracted. Sleeves are typically manufactured with external dimensions ranging from 114.3mm to 508.0mm.

Due to the harsh working conditions of the casing, the quality requirements of the steel are strict. Steel should be produced and inspected according to special standards or specifications. API Spec 5CT specifies the steel standard for casing.

J55 API-5CT casing is a relatively low grade of steel used in oil drilling. Widely used in shallow oil and gas exploration. Compared with other steel grades, it has low cost and a wider range of applications, and can generally be used in shallow wells, geothermal wells and water wells.

API-5CT K55 oilfield casing is very similar to J55, with no significant difference in chemical composition and yield strength, but the ultimate tensile strength of K55 is higher than that of J55 steel, with K55/J55 being 655MPa and 517MPa, respectively.

K55 has better mechanical and thermal fatigue and crack resistance than K55. For thermal recovery wells, thick-walled K55 casing should be used instead of J55 casing. The former has better thermal fatigue resistance than the latter.

API-5CT N80 oilfield casing includes N80-1 and N80-Q types. The chemical composition and mechanical properties of these two materials are completely the same, but the heat treatment is different.

During heat treatment, N80-1 steel is normalized and tempered, while N80Q steel is quenched and tempered. Therefore, the collapse resistance and internal pressure strength of N80Q are higher than those of N80-1. N80-1 or N80Q should be clearly marked by the designer when choosing N80 case.

Due to its higher mechanical properties than the J55 and K55 types, it can be used well in some of the more challenging formations. The downhole depth is deeper than J55 and K55, which can be used for middle-layer oil and gas exploitation.

Due to the high performance of the N80 material, these API-5CT casings are widely used in natural gas as well as coalbed methane extraction and geothermal wells.

L80 belongs to the corrosion resistant casing steel grade group. L80 API oilfield casing includes L80-1, L80-9Cr, L80-13Cr. L80-1 is used in H2S environments, while L80-9Cr and L80-13Cr are used in CO2 environments. In the corrosive environment dominated by carbon dioxide, the corrosion resistance of Super 13Cr is higher than that of L80-13Cr.

The price of this product is relatively high, and it is suitable for more complex geological conditions and deeper drilling depths. In oil and gas exploitation, the frequency of use of L80 is lower than that of J55, N80 and other materials.

P110 API-5CT steel casing is the highest grade among other steel grades. The finished case is marked with a white strip to indicate the material. In the process of oil drilling and production, this kind of pipe is generally used in various complex fields due to its high tensile strength and high yield strength.

Of the other types, it goes deepest into the well. But the price is relatively high and the usage is relatively small. P110 casing is mainly used in specific environments and when the drilling depth is extended to a specific level.

https://www.continental-steel.com/OCTG/Casing-Pipe.html