proved considerably as a result of improved drilling engineering. One fact is 

 certain: the development of the jet rock bit has brought about improved pene- 

 tration as a result of concentration of effort on improved drilling principles. 



FACTORS RELATED TO The use of the jet rock bit has brought about 



APPLICATION OF a change in the emphasis placed on the con- 



JET ROCK BITS trollable and established conditions of rotary 



oil-well drilling. 

 A definition and analysis of controllable and established conditions will 

 help clarify the application of jet bits. The conditions discussed here are those 

 that pertain directly to the power applied to the rock bit or that contribute to bit 

 performance. Established conditions referred to are those factors that are a 

 part of the oil-well drilling rig at the time the hole is drilled. They are as 

 follows: 



1. Rock-bit size (determined by casing program) 



2. Drill-pipe size 



3. Tool-joint size 



4. Drill collar 0. D. (outside diameter) 



5. Drill collar I. D. (inside diameter) 



6. Drill-collar length 



7. Stand-pipe size I. D. 



8. Stand-pipe length 



9. Length of discharge lines 



10. Size of discharge lines 



11. Kelly -hose I. D. 



12. Kelly-hose length 



13. Swivel-washpipe and fluid-passage I. D. and length 



14. Mud-pump characteristic - volume 



15. Mud-pump characteristic - pressure 



16. Hydraulic horsepower available 



17. Formations encountered in drilling the well 



Consideration must be given each of these factors in planning a jet-bit 

 program. 



The controllable conditions are those factors that may be varied or changed, 

 after drilling is begun, to meet the changing demands of the formation being 

 drilled and the increase in hole depth. These factors include: 



1. Slush-pump liner size 



2. Slush-pump strokes per minute 



3. Bit-nozzle diameter 



4. Number of bit nozzles 



5. Rotary-table r.p.m. 



656 



