The square drill pipe, drill pipe, weighted drill pipe and drill collar in the drilling tool form the drill column. Drill pipe is the core drilling tool to drive the drill bit from the ground to the bottom of the well, and it is also a channel from the ground to the bottom of the well. It has 3 main functions:
① Transmit torque to drive the drill bit to drill the well;
② Relying on its own weight to exert pressure on the drill bit to break the rock at the bottom of the well;
③ Conveying washing fluid, i.e. drilling mud through the high-pressure mud pump on the ground, into the borehole of the drilling column to flow into the bottom of the well to flush the rock chips and cool the drill bit, and carrying the rock chips through the annular space between the outer surface of the drilling column and the wall of the well to return to the ground, so as to achieve the purpose of drilling the well. Drill pipe in the drilling process to withstand a variety of complex alternating loads, such as tensile, compression, torsion, bending and other stresses, the inner surface is also subject to high-pressure mud scouring and corrosion.
(1) Square Drill Pipe: There are two types of square drill pipe: quadrilateral type and hexagonal type. Its specifications are: 63.5mm (2-1/2in), 88.9mm (3-1/2in), 107.95mm (4-1/4in), 133.35mm (5-1/4in), 152.4mm (6in) and so on. Usually the length used is 12~14.5m.
(2) Drill pipe: Drill pipe is the main tool for drilling wells, connected to the lower end of the square drill pipe, and as the drilling well continues to deepen, the drill pipe keeps lengthening the drill column one after another. The specifications of drill pipe 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) and so on.
(3) Weighted drill pipe: Weighted drill pipe is a transitional tool connecting drill pipe and drill collar, which can improve the force condition of drill pipe and increase the pressure on drill bit. The main specifications of 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 pipe, which is a special thick-walled pipe with high rigidity, exerting pressure on the drill bit to break the rock, and playing a guiding role when drilling a straight well. The common specifications of drill collar are: 158.75mm (6-1/4in), 177.85mm (7in), 203.2mm (8in), 228.6mm (9in) and so on.
