石油套管是用于支撐油、氣井井壁的鋼管，以保證鉆井過程進行和完井后整個油井的正常運行。每一口井根據不同的鉆井深度和地質情況,要使用幾層套管.套管下井后要采用水泥固井,它與油管、鉆桿不同，不可以重復使用，屬于一次性消耗材料.所以，套管的消耗量占全部油井管的70%以上。

按美國石油學會標準APISPEC5CT,套管可生產加工鋼級為J55,K55，N80,P110 等。規格從60--508 K55可加工扣型有STC(短圓扣),LC(長圓扣), BC(偏梯扣),VAM(偏梯扣)等扣型。

Petroleum casing is used to support the wellbore of oil and gaswells in order to ensure the normal operation of the whole well after drilling and ompletion. Each well should use several layers of casing according to different drilling depth and geological conditions. Cement cementing is used after casing goes down. It is different from tubing and drill pipe. It can not be reused. It belongs to disposable consumable material. Therefore, the consumption of casing accounts for more than 70% of all oil well pipes.

According to APIspec5ct standard of American Petroleum Society,casing can produce processed steel grade J55, K55, N80, p110, etc.Specifications from 60 to 508 K55 can be processed button type STC (short round buckle), LC (long round buckle), BC (partial ladder buckle), VAM (partial ladder buckle) and ther button type.