Seamless steel pipes are widely used in our daily lives, with a crucial application being the transmission of energy, including oil and natural gas, through pipelines. They can be laid not only on land but also underwater, greatly facilitating energy flow between different regions—a transportation method unmatched by land or sea transport.
In today’s society, protecting the security of energy pipelines is increasingly important. The damage to the Nord Stream pipeline had a significant impact, increasing living costs and seriously affecting regional security. As such a vital production resource, what makes oil transportation pipelines so special? Let’s learn about seamless steel oil casing pipes. Seamless steel oil casing pipes are the lifeline for maintaining oil well operations. They are mainly used to support the wellbore walls of oil and gas wells, ensuring the smooth operation of the drilling process and the overall normal functioning of the well after completion.
Oil tubing and casing differ from ordinary seamless steel pipes. Due to their application in more complex geological environments and varying geological conditions, the downhole stress states are complex, with tensile, compressive, bending, and torsional stresses acting on the pipe body, placing higher demands on the quality of the oil casing itself. In the API SPEC 5CT standard, the steel grade of oil tubing and casing indicates its yield strength and some special characteristics. The steel grade is typically represented by one letter and two or three numbers, such as N80.
In most cases, the later the letter in the alphabet, the greater the yield strength of the pipe. For example, the yield strength of N80 grade steel is greater than that of J55. The numerical symbol is determined by the minimum yield strength of the pipe material, expressed in thousands of pounds per square inch. For example, the minimum yield strength of N80 steel grade is 80,000 lb/in². The API SPEC 5CT standard lists the following oil well casing steel grades: H40, J55, K55, N80, M65, L80, C90, C95, T59, P110, and Q125; The other oil well casing steel grades are: H40, J55, N80, L80, C90, T59, and P110.
Each well requires several layers of oil well casing, depending on the drilling depth and geological conditions. After being run into the well, the oil well casing is cemented. Unlike tubing and drill pipe, it cannot be reused and is a disposable material. If the oil well casing itself is damaged for any reason, it may lead to reduced production or even the abandonment of the entire well. Therefore, the consumption of oil well casing accounts for more than 70% of all oil well tubing.
Post time: Jan-13-2026