The main standard of large-diameter J55 oil casing pipe
is API 5L, the outer diameter of large-diameter oil casing is expressed in inches, and 1b/ft is the unit of weight. The oil casing adopts different materials according to different strengths and well depths and conditions. The main materials are K55 oil casing, J55 oil casing, N80, P110 oil casing. The problems that often occur in large-diameter oil casings are broken buckles, damaged wire buckles, black buckles, pipe folds, and casing brittle fractures. "P" for large-diameter oil casing represents flat end, "L" represents long round buckle, "B" represents partial trapezoid buckle, and "S" represents short round buckle. The length of J55 oil casing is within 12 meters, and it can be processed according to the needs of customers.
Long round buckle oil casing, abbreviated as Ltc. in English, is a widely used buckle shape of oil casing. The thread shape at both ends of the pipe body is like an oblong shape, so it is called long round buckle oil casing.
There are three specified lengths of API long round buckle oil casing: R-1 is 4.88～7.62m, R-2 is 7.62～10.36m, R-3 is 10.36m to longer. The main materials include J55, K55, N80, L80, C90, T95, P110, Q125, V150. Among them, the H-40 steel grade is the lowest, and the P-110 steel grade has the highest strength. According to the different steel grades, the color of the casing is also different. The commonly used steel grades are J-55 painted green, N-80 painted red, and P-110 painted white.The mechanical properties of the three long round buckle oil casings are mainly hydrostatic pressure test, flattening test, sulfide stress corrosion cracking test, hardness test, tensile test and transverse impact test. Where the geological conditions are complex, the casing is also required to have anti-collapse properties. The oblong thread has the advantages of easy processing, good sealing, certain connection strength, simple on-site maintenance and use, and low price. It is widely used in casing connection.