A drill pipe is a steel tube featuring threaded ends, used to connect surface equipment at the drilling rig with the drilling assembly or bottom-hole assembly located at the bottom of the wellbore. The primary functions of the drill pipe are to transport drilling fluid to the drill bit and, in conjunction with the bit, to raise, lower, or rotate the bottom-hole assembly. Drill pipes must be capable of withstanding immense internal and external pressures, torsional stresses, bending forces, and vibrations. In the process of oil and gas exploration and production, drill pipes are designed for repeated use. Drill pipes are broadly classified into three categories: kelly pipes, standard drill pipes, and heavy-weight drill pipes. The typical connection sequence is: Kelly pipe (1 joint) + Standard drill pipes (*n* joints-quantity determined by well depth) + Heavy-weight drill pipes (*n* joints-quantity determined by the drill string design). This text provides a detailed overview of drill pipe classification, drill pipe joints, specifications, and the various steel grades and strength ratings associated with drill pipes.
The typical components of a drill string include: the drill bit, drill collars, drill pipes, stabilizers, specialized subs (adapters), and the kelly pipe.
The fundamental functions of the drill string are:
(1) To run the drill bit into and out of the wellbore;
(2) To apply weight on bit (drilling pressure);
(3) To transmit rotational power;
(4) To circulate drilling fluid;
(5) To facilitate special operations, such as squeeze cementing or resolving downhole complications.
The product range encompasses API standard steel grades from E75 to S135-with outer diameters ranging from 2 3/8″ to 6 5/8″-as well as drill pipes featuring double-shoulder connections for enhanced torsional strength, and specialized BNK C95S steel-grade drill pipes designed for use in sour (sulfur-bearing) wells. These products are primarily utilized in the construction of deep wells, horizontal wells, and extended-reach wells during oil and gas exploration and development operations.