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APPENDIX B

Minimum Gas Flow Rates

Required for Lifting Solids

and Water in Air Drilling

Well geometry
Total measured depth: 400~1,5000 ft
Bit diameter: 4.75~9.875 in
Drill pipe OD: 2.375~5 in
Material properties
Specific gravity of rock: 2.75 (water = 1)
Specific gravity of gas: 1 (air = 1)
Gas specific heat ratio: 1.25
Specific gravity of oil: 1 (water = 1)
Specific gravity of formation water: 1.07 (water = 1)
Pipe roughness: 0.0018 in
Borehole roughness: 0.1 in
Environment
Site elevation: 0 ft
Ambient pressure: 14.7 psia
Ambient temperature: 60ºF
Relative humidity: 0 fraction
Geothermal gradient: 0.01 F/ft
Operating conditions
Surface choke/flow line pressure: 14.7 psia
Rate of penetration: 60~120 ft/hour
Rotary speed: 50 rpm
Oil influx rate: 0 bbl/hour
Water influx rate: 4–24 bbl/hour
Interfacial tension: 40~60 dynes/cm

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