Casing and tubing are the core OCTG components used in oil and gas wells. Casing stabilizes the wellbore and isolates formations, while tubing provides a removable flow path for production or injection fluids. Most projects specify API 5CT / ISO 11960 for grades, dimensions and testing, with casing connections such as STC/LTC/BTC and tubing connections such as NU/EUE or premium gas-tight threads depending on pressure, corrosion (H?S/CO?) and well design.
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