Introduction to seamless steel pipe oil casing

Seamless pipes are widely used in our daily lives. One of the very important application areas is as an energy channel for us to transmit energy, including oil, natural gas, etc. It can be laid not only on land, but also on the seabed, which brings great convenience to the flow of energy in different regions. It is a transportation method that is unmatched by land and sea transportation.

Oil pipelines are a crucial means of production. This article will examine the importance of seamless steel pipes in oil casing pipes.

Oil casing is essential for maintaining the operation of oil wells. Its primary function is to support the well wall of oil and gas wells, ensuring the drilling process and normal operation of the entire well after completion.

Oil pipes and casing differ from ordinary seamless steel pipes due to the complex geological environment and varying conditions. The downhole stress state is complex, with the combined effects of tension, compression, bending and torsion stress on the oil pipe body and casing itself. Therefore, high quality requirements must be met.

The API SPEC 5CT standard defines the steel grade of casing and tubing based on its yield strength and other special properties. Typically, the steel grade is denoted by a letter followed by two or three numbers. For instance, N80 represents a specific steel grade.

In general, higher yield strength is represented by letters later in the alphabetical order. For instance, N80 Grade 1 steel has a higher yield strength than J55. The numerical sign corresponds to the minimum yield strength of the pipe, expressed in thousands of pounds per square inch. For example, the N80 grade has a minimum yield strength of 80,000lb/in2. The API SPEC 5CT standard specifies the casing grades listed below: H40, J55, K55, N80, M65, L80, C90, C95, T59, P110 and Q125. H40, J55, N80, L80, C90, T59 and P110. The following casing steel grades are included: The casing grades are: It is important to maintain consistency in the use of casing steel grades throughout the document.

Each well uses multiple layers of casing at different drilling depths and geological conditions. Cement is used to cement wells after casing is lowered into the well. Unlike oil pipes and drill pipes, cement cannot be reused and is a one-time consumable material. If the casing is damaged, the well production may be reduced or even scrapped. Therefore, casing consumption accounts for more than 70% of all oil well tubing.