There are three kinds of drill collars, slick drill collars, spiral drill collars, and non-magnetic drill collars.
Slick Drill collars
Slick drill collars are made of AISI 4145 or 4145H modified alloy steel with full length heat treatment process, which ensures the mechanical properties meet API SPEC 7 and a hardness of 285-341 HB.
Dimensions of standard drill collar
Drill collar | Outside diameter c | Bore | Length | Bevel diameter | Reference | ||
number | D mm | d | L | DF | bending strength | ||
and | mm | m | mm | ratio | |||
connection label | +1 ,5 9 0 | ± 152,4 mm d | ± 0,4 mm | BSR e | |||
NC23 – 31 | 3 1/8" | 79,4 | 1 1/4" | 31,8 | 9,14 | 76,2 | 2,57:1 |
NC 26 – 35 | 3 1/2" | 88,9 | 1 1/2" | 38,1 | 9,14 | 82,9 | 2,42:1 |
NC31 – 41 | 4 1/8" | 104,8 | 2" | 50,8 | 9,14 or 9,45 | 100,4 | 2,43:1 |
NC 35 – 47 | 4 3/4" | 120,6 | 2" | 50,8 | 9,14 or 9,45 | 114,7 | 2,58:1 |
NC 38 – 50 | 5" | 127,0 | 2 1/4" | 57,2 | 9,14 or 9,45 | 121,0 | 2,38:1 |
NC 44 – 60 | 6" | 152,4 | 2 1/4" | 57,2 | 9,14 or 9,45 | 144,5 | 2,49:1 |
NC 44 – 60 | 6" | 152,4 | 2 13/16" | 71,4 | 9,14 or 9,45 | 144,5 | 2,84:1 |
NC 44 – 62 | 6 1/4" | 158,8 | 2 1/4" | 57,2 | 9,14 or 9,45 | 149,2 | 2,91:1 |
NC46 – 62 | 6 1/4" | 158,8 | 2 13/16" | 71,4 | 9,14 or 9,45 | 150,0 | 2,63:1 |
NC46 – 65 | 6 1/2" | 165,1 | 2 1/4" | 57,2 | 9,14 or 9,45 | 154,8 | 2,76:1 |
NC46 – 65 | 6 1/2" | 165,1 | 2 13/16" | 71,4 | 9,14 or 9,45 | 154,8 | 3,05:1 |
NC46 – 67 | 6 3/4" | 171,4 | 2 1/4" | 57,2 | 9,14 or 9,45 | 159,5 | 3,18:1 |
NC 50 – 70 | 7" | 177,8 | 2 1/4" | 57,2 | 9,14 or 9,45 | 164,7 | 2,54:1 |
NC 50 – 70 | 7" | 177,8 | 2 13/16" | 71,4 | 9,14 or 9,45 | 164,7 | 2,73:1 |
NC50 – 72 | 7 1/4" | 184,2 | 2 13/16" | 71,4 | 9,14 or 9,45 | 169,5 | 3,12:1 |
NC56 – 77 | 7 3/4" | 196,8 | 2 13/16" | 71,4 | 9,14 or 9,45 | 185,3 | 2,70:1 |
NC56 – 80 | 8" | 203,2 | 2 13/16" | 71,4 | 9,14 or 9,45 | 190,1 | 3,02:1 |
6 5/8 REG | 8 1/4" | 209,6 | 2 13/16" | 71,4 | 9,14 or 9,45 | 195,6 | 2,93:1 |
NC61 – 90 | 9" | 228,6 | 2 13/16" | 71,4 | 9,14 or 9,45 | 212,7 | 3,17:1 |
7 5/8 REG | 9 1/2" | 241,3 | 3" | 76,2 | 9,14 or 9,45 | 223,8 | 2,81:1 |
NC70 - 97 | 9 3/4" | 247,6 | 3" | 76,2 | 9,14 or 9,45 | 232,6 | 2,57:1 |
NC70– 100 | 10" | 254,0 | 3" | 76,2 | 9,14 or 9,45 | 237,3 | 2,81:1 |
8 5/8 REG | 11" | 279,4 | 3" | 76,2 | 9,14 or 9,45 | 266,7 | 2,84:1 |
Mechanical properties of drill collars
OutsideDiameter | OutsideDiameter | TensileStrength | YieldStrength | Elongation(L=4D) | ImpactAKV | BrinellHardness |
3 1/8-6 3/4 | 79.4-171.4 | ≥965 | ≥758 | ≥13 | ≥54 | ≥285 |
0 | 177.8-254 | ≥930 | ≥689 | ≥13 | ≥54 | ≥285 |
Spiral grooved Drill Collar
OD Range (in) | 4-4 3/8 | 4 1/2-5 1/8 | 5 1/4-6 3/8 | 6 1/2-7 | 7 1/8-7 7/8 | 8-8 7/8 | 9-9 7/8 |
Depth of cut (in) | 6 2/3± 1/32 | 7/32± 1/32 | 1/4± 1/32 | 5/16± 1/16 | 11/32± 1/16 | 3/8± 1/16 | 13/32± 3/32 |
Spiral Pitch (in) | 36 ± 1 | 38 ± 1 | 42 ± 1 | 42 ± 1 | 64 ± 1 | 68 ± 1 | 72 ± 1 |
Non-Magnetic Drill Collar
Non-magnetic drill collars are made of low chrome manganese and low carbon alloy steel. The chemical composition is strictly controlled during the refining and forging process, with favorable low magnetic permeability, high strength of mechanical properties and outstanding resistant to stress corrosion cracking and no tendency to galling.