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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, |
| 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 3: Minimum Performance Properties of Grade E Drill Pipe (after API Bul 5C2) | ||||
|---|---|---|---|---|
| Outside diameter, in. | Nominal weight, |
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 |
| 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 |
| 19.50 | 10,000 | 9500 | 396,000 | |
| 5.50 | 21.90 | 8440 | 8610 | 437,000 |
| 24.70 | 10,460 | 9900 | 497,000 | |
| 6.625 | 25.20 | 4810 | 6540 | 489,000 |
