Page 220 - Air and gas Drilling Field Guide 3rd Edition

References 211

in Chapter 5. Appendix C gives the Mathcad solution for Illustrative Example 8.3.
In this solution, the fuel consumption calculations found in Chapter 5 were
applied to the Illustrative Example 8.3 solution. The fuel consumption rate
required for the Caterpillar Model D398 diesel fueled prime mover of the Dresser
Clark CFB-4 compressor operating at an air injection pressure required for drilling
at 10,000 ft (3048 m) of depth is approximately 32 gal/hr (120 liters/hr). The
total diesel fuel usage rate for all three compressors on the location is approxi-
mately 95 gal/hr.

8.6 CONCLUSIONS
The discussions in this chapter concentrated on direct circulation operations. The
Mathcad illustrative examples in Appendix C utilized lumped geometry approxi-
mations for the drill pipe body and drill pipe tool joints. These approximations
appear to adequately model the overall friction resistance along the circulation
system and give accurate results for bottom hole and injection pressures.
Unlike the aerated and stable foam drilling fluids, which are discussed in
Chapters 9 and 10, the modeling of air drilling fluids is not a rheology issue.
The major issues with air drilling fluids are (1) downhole combustion and
(2) the ability of the air drilling fluid to carry formation water from the well.
The first issue has been solved by the membrane filter technology used to pro-
duce an inert atmospheric air that is defined in this text as membrane generated
nitrogen. The second issue can only be solved in the field by experienced drilling
personnel.
With all things being equal, air drilling fluid will have the lowest bottom hole
pressure of the three drilling fluids being considered in this text: air, aerated, and
stable foam.

REFERENCES
1. Angel, R. R., “Volumetric Requirements for Air or Gas Drilling,” Petroleum Transactions,
AIME, 1957.
2. Angel, R. R., Volume Requirements for Air and Gas Drilling, Gulf Publishing Company,
1958.
3. Lyons, W. C., Air and Gas Drilling Manual, Second Edition, McGraw-Hill Company, 2001.
4. Ikoku, C. U., and Williams, C. R., “Drill Cuttings Transport in Vertical Annuli by Air, Mist and
Foam in Aerated Drilling Operations,” Contracts for Field Projects and Supporting Research
on Enhanced Oil Recovery and Improved Drilling Technology: Progress Review No. 24,
February 1981.
5. Machado, C. J, and Ikoku, C. U., “Experimental Determination of Solids Fraction and
Minimum Volumetric Requirements in Air and Gas Drilling,” Journal of Petroleum
Technology, November 1982.