OCTG Casing

OCTG casing is a large-diameter steel tubular used in oil and gas wells for drilling, completion, and production. It lines the wellbore to provide structural support, prevent formation collapse, isolate pressure zones, and protect groundwater from contamination. Manufactured by seamless extrusion or electric resistance welding (ERW), casing is made from high-strength carbon and low-alloy steels. Diameters typically range from 4½" to 20" (114.3 mm – 508 mm), with segments approximately 30 feet long and threaded connections for secure installation. Casing accounts for approximately 77% of the entire OCTG pipeline system.

OCTG Tubing

OCTG tubing is a small-diameter steel pipe inserted inside the casing string through which reservoir fluids (oil, gas, and water) are produced to the surface. It is also used for injection of water, gas, or chemicals into the formation for enhanced recovery. Tubing is manufactured by seamless or ERW processes, with diameters ranging from 1.900" to 4½" (48.3 mm – 114.3 mm). It is typically supplied in lengths of approximately 30 feet with threaded connections. Unlike casing, tubing is subject to repeated tension, pressure cycling, and corrosive fluids, requiring higher mechanical strength and corrosion resistance.