| IADC |
Rock formation |
WOB (KN/mm) |
PRM(r/min) |
| 417/427/437 |
Low compressive strength, high drill-ability and extremely soft formation, like shale, clay, sandstone,etc. |
0.35~0.90 |
140~70 |
| 447 |
Low compressive strength, high drill-ability and soft formation, like shale, clay, sandstone, soft limestone, salt rock, plaster etc. |
0.37~1.00 |
140~60 |
| 517 |
Low compressive strength, high drill-ability and soft formation, like shale, clay, sandstone, soft limestone, salt rock, etc. |
0.37~1.05 |
120~50 |
| 527 |
Soft formation with low compressive, like Low compressive strength, high drill-ability and soft formation, like shale, clay, sandstone, soft limestone, salt rock, anhydrite etc. |
0.35~1.05 |
120~50 |
| 537/547 |
Low compressive strength, medium hard formation with hard abrasive interlayer, like Hard shale, anhydrite, soft limestone, sandstone, dolomite with mezzanine, etc. |
0.50~1.05 |
110~40 |
| 617/627 |
High compressive strength, medium hard and thick hard interlayer, like hard shale, limestone, sandstone, dolomite, etc. |
0.50~1.05 |
80~40 |
| 637/737 |
High compressive strength, medium hard and high abrasive formation, like limestone, dolomite, sandstone, chert, etc. |
0.7~1.20 |
70~40 |
