OCTG Casing and Tubing are essential tubulars.

OCTG Casing and Tubing are essential tubulars.
Production tubing is normal nowadays into the well casing pipe in the well. Flowing wells, oil flows into the ground through the tubing into the gathering process. Apheresis wells, tubing, sucker rod deep well pump (ie, "three pumping" device) combination, the oil pumped to the surface, into the gathering process.
At the end of the sleeve is drilling down into the underground pipe, OCTG Casing  and cementing wall with cement, and then with the alignment target layer
perforating guns, the oil flow through the rock, cement, casing into the well bottom, then enter the tubing to the ground.