This appendix provides engineering charts for determining the minimum required air injection rate for drilling directional borehole sections. The engineering charts were generated based on the following assumptions:

• Direct circulation method used

• Generic hole trajectory is arc-shaped path ( circle)

• Specific gravity of cuttings = 2.70 (water = 1)

• Average borehole roughness = 0.1 in.

• Minimum specific kinetic energy required for hole cleaning = 3 lb-ft

• Ambient pressure = 14.7 psia

• Ambient temperature = 60 F

• Geothermal gradient = 0.01 F/ft

• Relative air humidity = 0%

• Air flow rates given in API standard atmospheric conditions (14.696 psia and 60 F)

These charts can also be used for reverse circulation methods in low ROP conditions if the equivalent cross-sectional area of the flow path is used. Corrections for misting fluid and formation fluid influx can be made by converting the fluid into equivalent ROP using equation (2.38).

Figure C-1: Minimum Required Air Flow Rate for 17 in. Borehole and 6 ? in. Drillpipe

Figure C-2: Minimum Required Air Flow Rate for 15 in. Borehole and 6 ? in. Drillpipe

Figure C-3: Minimum Required Air Flow Rate for 12 in. Borehole and 6 ? in. Drillpipe

Figure C-4: Minimum Required Air Flow Rate for 11 in. Borehole and 6 ? in. Drillpipe

Figure C-5: Minimum Required Air Flow Rate for 9 ? in. Borehole and 5 in. Drillpipe

Figure C-6: Minimum Required Air Flow Rate for 9 in. Borehole and 5 in. Drillpipe

Figure C-7: Minimum Required Air Flow Rate...