API: it is the abbreviation of American Petroleum Institute, which means American Petroleum Institute in Chinese. OCTG: it is the abbreviation of oil country tubular goods in English, which means special oil pipe in Chinese, including product oil casing, drill pipe, drill collar, coupling, short connection, etc.

Tubing: tubing used in oil wells for oil production, gas production, water injection and acid fracturing

Casing: a pipe that runs into a drilled hole from the ground surface as a lining wall to stop the collapse of the well wall.

Drill pipe: pipe used for drilling hole. Pipeline pipe: a pipe used to transport oil and gas.

Coupling: a cylindrical body with internal threads used to connect two threaded pipes.

Coupling material: pipe used to make coupling. API thread: pipe thread specified in API 5B standard, including tubing round thread, casing short round thread, casing long round thread, casing partial trapezoidal thread, pipeline pipe thread, etc.

Special buckle: non API thread buckle type with special sealing performance, connection performance and other properties.

Failure: deformation, fracture, surface damage and loss of original function under specific service conditions. The main forms of oil casing failure are: collapse, slippage, rupture, leakage, corrosion, bonding, wear and so on.