Drill pipe is an essential part of the drill string. It is generally made of seamless steel pipe (wall thickness range 9~11mm), which is composed of two parts: drill pipe body and drill pipe joint. Its main function is to transfer torque and drilling fluid, and by the gradual lengthening of the drill pipe to deepen the well. In simple terms, a drill pipe is a steel pipe with a thread at the end. The bare pipe is made into a drill pipe after several machining steps. Drill pipe is divided into kelly, drill pipe and weighted drill pipe. The connection order is Kelly (1 piece)+ drill pipe (n pieces, determined by the oil well depth)+ weighted drill pipe (n pieces, determined by the design of the drill assembly).
API drill pipe is designed to provide maximum strength, bending, and tensile strength for deep wells to recover natural gas and oil. This required it has the ability to endure great external pressure as well as the flexibility to transmit torque to the drilling rig and mill equipment. In order to enhance the connection strength between the tube body and the joint, both ends of the tube body are thickened. Commonly used thickening forms are internal upset(IU), external Upset(EU), internal and external upset(IEU). The diameter of a drill pipe is primarily determined by the borehole’s diameter. It is then categorized by the American Petroleum Institute (API). There are three basic ranges of API drill pipe. These ranges are Standard range 1, Range 2 and Range 3. These are the most common sizes, though custom lengths are sometimes available.
- Range 1，5.486~6.706m(18~22ft)；
- Range 2，8.230~9.144m(27~30ft)；
- Range 3，11.582~13.716m(38~45ft)；
Drill pipe can also be classified by outside diameter size. Common drill pipe sizes are 60.3mm, 73mm, 88.9, 101.6mm, 114.3, 127mm, and 139.7mm (imperial: 2 3/8”, 2 7/8”, 3 1/2” 4”, 4 1/2”, 5”, 5 1/2” up to 6 5/8”).
API Drill Pipe Size Chart
|Size||Nominal weight||Flat end weight||Steel grade||W.T||Upset|
|2 3/8||60.3||6.65||6.26||9.32||E, X, G, S||0.28||7.11||EU|
|2 7/8||73||10.4||9.72||14.48||E, X, G, S||0.362||9.19||EU 、 IU|
|3 1/2||88.9||9.5||8.81||13.12||E||0.254||6.45||EU 、 IU|
|3 1/2||88.9||13.3||12.31||18.34||E, X, G, S||0.368||9.35||EU 、 IU|
|3 1/2||88.9||15.5||14.63||21.79||E||0.449||11.4||EU 、 IU|
|3 1/2||88.9||15.5||14.63||21.79||X, G, S||0.449||11.4||EU 、 IEU|
|4||101.6||14||12.93||19.26||E, X, G, S||0.33||8.38||EU 、 IU|
|4 1/2||114.3||13.75||12.24||18.23||E||0.271||6.88||EU 、 IU|
|4 1/2||114.3||16.6||14.98||22.31||E, X, G, S||0.337||8.56||EU 、 IEU|
|4 1/2||114.3||20||18.69||27.84||E, X, G, S||0.43||10.92||EU 、 IEU|
|5||127||16.25||14.87||22.15||X, G, S||0.296||7.52||IU|
|5||127||19.5||17.93||26.71||X, G, S||0.362||9.19||EU 、 IEU|
|5||127||25.6||24.03||35.79||X, G, S||0.5||12.7||EU 、 IEU|
|5 1/2||139.7||21.9||19.81||29.51||E, X, G, S||0.361||9.17||IEU|
|5 1/2||139.7||24.7||22.54||33.57||E, X, G, S||0.415||10.54||IEU|