Drill Pipe

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Dimensions and Strengths

Like other oilfield tubulars, drill pipe comes in a variety of lengths, diameters, weights and grades of steel. Drill pipe is also specified according to its upset (the type of end section provided for weld-on connections or tool joints). Factors that influence drill pipe selection include:

Hole size
Well depth
Casing and cementing requirements
Subsurface pressures
Circulating system and drilling mud parameters
Hoisting capacity of drillng rig
Pipe availability and rental cost
Contract provisions

The American Petroleum Institute has established standards for drill pipe manufacturing practices, dimensions, strengths and performance properties. These standards appear in the following publications:

API Spec 5DP/ISO 11961: Specification for Drill Pipe
API Bul 5C2: Bulletin on Performance Properties of Casing, Tubing and Drill Pipe
API RP 7G: Recommended Practice for Drill Stem Design Operating Limits

Size and Weight

API-standard drill pipe is available in three length ranges:

Range 1(18-22 ft)
Range 2 (27-30 ft)
Range 3 (38-45 ft).

The most commonly used length is Range 2. Thus, the typical “average” length of a joint of drill pipe is about 30 feet, or just under 10 meters.

Table 1 lists outside diameters and nominal weights for API standard drill pipe (note that these diameters and weights apply only to the drill pipe tube, and do not include the weights and diameters of tool joints and upsets). This information is available in API Spec 5DP and API RP 7G.

Table 1: API Standard Drill Pipe Diameters and Weights
Outside diameter, inches	*Nominal weights, $\tfrac{lb}{ft}^$**
2.875	10.40
3.5	9.50 13.30 15.50
4	14.00
4.5	13.75 16.60 20.00
5	16.25 19.50 25.60
5.5	21.90 24.70
6.625	25.20 27.70

Strength

The strength of a joint of drill pipe is defined in terms of :

Pipe body yield strength: a measure of the pipe’s resistance to axial tension
Collapse resistance: a measure of the pipe’s ability to withstand external pressure
Internal yield pressure: a measure of the pipe’s ability to withstand internal pressure.

The values of these parameters depend on the grade of steel used to manufacture the pipe, and on the pipe’s size and weight per unit length. Table 2 lists some of the standard grades of steel used in drill pipe, along with their minimum yield strengths, while Table 3 shows how drill pipe strength (Grade E in this case) varies with diameter and weight.

Grade	Minimum Yield, psi
E	75,000
X-95	95,000
G-105	105,000
S-135	135,000
V-150	150,000

Table 2: API Standard Steel Drill Pipe Grades

Table 3: Minimum Performance Properties of Grade E Drill Pipe (after API Bul 5C2)
Outside diameter, in.	Nominal weight, $\tfrac{lb}{ft}$	Collapse Resistance, psi	Internal Yield Pressure, psi	Pipe Body Yield Strength, lb
2.375	6.65	15,600	15,470	138,000
2.875	10.40	16,510	16,530	214,000
3.50	9.50	10,040	9520	194,000
	13.30	14,110	13,800	276,000
	15.50	16,770	16,840	323,000
4.00	11.85	8410	8600	231,000
4.00	14.00	11,350	10,830	285,000
4.50	13.75	7200	7900	270,000
	16.60	10,390	9830	331,000
	20.00	12,960	12,540	412,000
5.00	16.25	6970	7770	328,000
5.00	19.50	10,000	9500	396,000
5.50	21.90	8440	8610	437,000
5.50	24.70	10,460	9900	497,000
6.625	25.20	4810	6540	489,000