Tubing is used to extract fluid and gas from wells, to inject water and compressed air (gas) and to perform various types of workover and workover operations. They are made in two types: with smooth and flared ends, where the external thread is cut and a coupling socket is screwed on one end. Markings shall be stamped at 0.4-0.6 m from the pipe end at the couplings side. The brand marking specifies pipe nominal diameter, mm, pipe grade, wall thickness, mm, trade mark, month and year of manufacture. Smooth pipes and couplings are made from steel of strength groups K, E, L, M, and the pipes with upset ends - from steel of strength groups D, K, E, L, M. Their threaded surfaces are covered with grease, which ensures tightness of connection and protects from galling and corrosion. The muffless tubing strings (NKB) provide leak-proof joints at pressures up to 50 mPa. The ends are molded to the outside, and the joint is very strong. Tightness of connections is provided by conical sealing surfaces, located behind threads on the side of smaller diameters. Trapezoidal threads are used in pipe connection. Socket tubing (SCP) provides tightness of connections at pressures up to 50 mPa. The strength of joints is up to 90% of the strength of the pipe body. Trapezoidal threads are used to connect the pipes. Tubing made of aluminum alloys. Resistant to hydrogen sulfide corrosion, which eliminates the use of corrosion inhibitors. Due to their low weight, the specific strength of aluminum tubing is 2.5 times that of steel tubing. This makes it possible to make a string 2.5 times longer than a string made of steel pipes. Tubing with protective coatings is used to prevent deposits of paraffin, salts and gypsum, as well as to protect it against corrosion. The use of these tubing reduces the number of current well workovers and extends their service life. The inner surface of tubing is coated with liquid glass, enamels, epoxy resins or varnishes. The most widespread coating is vitrified tubing.
Fiberglass tubing is used in injection wells of RPM system; disposal wells; gas lift wells; production wells with ESPs.
