| IADC | Recommendation |
Applicable Formation |
|
| WOB KN/mm (bit dia.) | Rotary Speed (rpm) | ||
| 437 / 447 | 0.35～0.9 | 240～70 | Very soft formations with low compressive strength and high drillability, such as clay, mudstone, chalk, gypsum, salt, soft shale, soft limestone, etc. |
| 517 / 527 | 0.35～1.0 | 220～60 | Soft formations with low compressive strength and high drillability, such as mudstone, gypsum, salt, soft shale, soft limestone, etc. |
| 537 / 547 | 0.45～1.0 | 220～50 | Soft to medium formations with low compressive strength, such as medium soft shale, medium soft limestone, medium soft sandstone, medium formation with harder and abrasiver interbed, etc. |
| 617 | 0.45～1.1 | 200～50 | Medium hard formations with high compressive strength, such as hard shale, limestone, sandstone, dolomite, etc. |
