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

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

The API-5CT casing steels commonly used in oil fields are J55, K55, N80-1, N80Q and P110. Casing is mainly used in oil well drilling. According to API-5CT, pipes can be classified as STC(short thread), LTC(long thread), and BTC(support thread) and their joints.

The field casing is placed in the wellbore and held in place to prevent subsurface formation and wellbore collapse, while also allowing drilling mud circulation and extraction. External casing sizes range from 114.3mm to 508.0mm.

Due to the bad working conditions of the casing, the steel quality is very strict. Steel shall be manufactured and inspected according to special standards or specifications.
The J55 API-5CT casing is a relatively low-grade steel used in oil drilling. It is widely used in shallow oil and gas exploration. Compared with other steel grades, the cost is low and the application range is wide. Generally, it can be used in shallow Wells, geothermal Wells and water Wells.

API-5CT K55 casing is very similar to J55 casing, with no significant difference in chemical composition and yield strength. However, 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, thermal fatigue and crack resistance than K55. For thermal recovery Wells, K55 thick-walled casing should be used instead of J55 casing. The former has better thermal fatigue resistance than the latter.

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

During heat treatment, N80-1 steel is normalized and N80Q steel is tempered. Therefore, the collapse resistance and internal compressive strength of N80Q are higher than those of N80-1. When selecting the N80 housing, the N80-1 or N80Q shall be clearly identified by the designer.

Due to its higher mechanical properties than J55 and K55, it can be well applied to some of the more challenging formations. The downhole depth is greater than that of J55 and K55, allowing for mid-zone oil and gas production.

Due to the high performance of the N80 material, API-5CT casing is widely used in natural gas, coalbed methane and geothermal Wells.

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

The product is relatively expensive and is suitable for more complex geological conditions and deep drilling depths. In oil and gas production, L80 is used less frequently than J55, N80 and other materials.

The P110 API-5CT steel casing is the highest of the other steel grades. Finished bins are marked with white bars to indicate materials. In the oil drilling and production process, this kind of tube has high tensile strength and yield strength, generally used in a variety of complex fields.

In other types, it goes to the deepest part of the well. But the price is relatively high and the usage is relatively small. The P110 casing was designed to be used in specific environments and extended to specific levels of depth.