Large caliber oil casing is divided into J55, K55, N80, L80, P110, Q125 and other more than ten kinds according to steel grade, according to the processing form of pipe end is divided into short round thread, long round thread, partial ladder thread, special buckle and other forms, which has the advantages of reducing cost, high safety and long service life. Different well conditions and well depths, the steel grades used are also different, and the casing itself is required to have corrosion resistance in special environments, and the casing is also required to have crush resistance in places with complex geological conditions.
