Classification and application of drill pipe

The kelly, DRILL PIPE, weighted drill pipe and drill collar in the drill tool constitute the drill string. The drill string is the core drilling tool that drives the drill bit from the surface to the bottom of the hole, as well as the passage from the surface to the bottom of the hole. It has three main functions: (1) transfer torque, drive the bit drilling; (2) Rely on the weight of the bit to exert pressure on it to break the rock at the bottom of the well; (3) Well flushing fluid transportation, that is, drilling mud through the high pressure mud pump on the ground into the drill string hole, into the bottom hole to wash cuttings and cool the drill bit, and through the outer surface of the drill string and the ring space between the wall to bring the cuttings back to the ground, so as to achieve the purpose of drilling. During the drilling process, the drill string has to withstand various complex alternating loads, such as tension, pressure, torsion, bending and other stresses, and the inner surface also has to withstand the erosion and corrosion of high-pressure mud.
⑴ Kelly: There are two types of kelly: Kelly and hexagonal. In China, square drill pipe is usually used for each group of oil drill pipe. Specifications :63.5mm (2-1/2in), 88.9mm (3-1/2in), 107.95mm (4-1/4in), 133.35mm (5-1/4in), 152.4mm (6in), etc. Generally, the length is 12 to 14.5m.
(2) Drill pipe: Drill pipe is the main tool of drilling and is connected with the lower end of kelly pipe. As the drill goes deeper, the drill pipe lengthens the drill string one by one. Drill pipe specifications are 60.3mm (2-3/8in), 73.03mm (2-7/8in), 88.9mm (3-1/2in), 114.3mm (4-1/2in), 127mm (5in), 139.7mm (5-1/2in), etc.
(3) Weighted drill pipe: Weighted drill pipe is a transition tool connecting drill pipe and drill collar, which can improve the stress condition of drill pipe and increase the pressure borne by drill bit. The main specifications for weighted drill pipe are 88.9mm (3-1/2in) and 127mm (5in).
(4) Drill collar: The drill collar is connected to the lower part of the drill string. It is an extra-thick tube wall with high rigidity that applies pressure to the drill bit to break the rock. It can be used as a guide in drilling vertical Wells. Commonly used drill collars are 158.75mm (6-1/4in), 177.85mm (7in), 203.2mm (8in), 228.6mm (9in), etc.