STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

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Air and Gas Drilling 843
Air and Gas (Dusting)
Advantages
No loss-of-circulation problem
No formation damage
Very high penetration rate
Low bit costs
Low water requirement
No mud requirement
Disadvantages
No ability to counter subsurface pore
pressure problems
Little ability to carry formation water
from hole
Hole erosion problems are possible if
formations are soft
Possible drill string erosion problems
Downhole fires are possible if hydrocarbons
are encountered (gas only)
Specialized equipment necessary
Unstable Foam (Mlsting)
Advantages
No loss-of-circulation problem
Ability to handle some formation water
No formation damage
Very high penetration rate
Low bit costs
Low water requirement
No mud requirement
Low chemical additive costs
Downhole fires are normally not a
problem even with air
Disadvantages
Very little ability to counter subsurface
pore pressure problems
No ability to carry a great deal of
formation water from hole
Hole erosion problems are possible if
formations are soft
Possible drill string erosion problems
Specialized equipment necessary
Stable Foam
Advantages
No loss-of-circulation problem
Ability to handle considerable formation
water
Little or no formation damage
High penetration rate
Low bit costs
Low water requirements
No mud requirements
Some ability to counter subsurface
pore pressure problems
Dlsadvantages
Considerable additive (foamer) costs
Careful and continuous adjusting of
proportions necessary
Specialized equipment necessary
Aerated Mud
Advantages
Loss of circulation is not a big
problem
Ability to handle very high volumes of
formation water
Disadvantages
High mud pump pressure requirements
High casinglair line costs if parasite
tubing is used
Some specialized equipment