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Appendix B – Minimum Gas Flow Rates 235

4000
Minimum Required Air Injection Rate (scfm) 3000 Q =4 bbl/hour
3500

2500
2000
w
Q =8 bbl/hour
1500
w
Q =12 bbl/hour
w
1000
Q =16 bbl/hour
w
w
500
Q =24 bbl/hour
w
For cuttings removal
0 Q =20 bbl/hour
0 2000 4000 6000 8000 10000 12000 14000 16000
Depth (ft)
Figure B.3 Calculated air injection requirements for drilling a 7⅞-in hole with a 4½-in
drill pipe at an ROP of 60 ft/hr (water-air interfacial tension = 40 dynes/cm).

6000
Minimum Required Air Injection Rate (scfm) 4000 Q =4 bbl/hour
5000

3000
w
Q =8 bbl/hour
w
2000
Q =12 bbl/hour
w
Q =16 bbl/hour
w
Q =20 bbl/hour
1000
w
Q =24 bbl/hour
w
For cuttings removal
0
0 2000 4000 6000 8000 10000 12000 14000 16000
Depth (ft)
Figure B.4 Calculated air injection requirements for drilling a 9⅞-in hole with a 5-in
drill pipe at an ROP of 60 ft/hr (water-air interfacial tension = 60 dynes/cm).