STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

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844 Drilling and Well Completions
Advantages
Improved penetration rates (relative to
mud drilling)
Ability to counter high subsurface pore
Dressure Droblems
Aerated Mud (continued)
Disadvantages
The listing is basically in descending order in terms of ability to counter lossof-circulation
problems (i.e., air and gas being the most useful technique) and
a lack of causing formation damage (Le., air and gas cause no formation
damage). The listing is in ascending order in terms of ability to carry formation
water from the hole and ability to counter subsurface pore pressure.
Equipment
Surface and subsurface specialized equipment are required for air and gas
drilling operations.
Surface Equipment
Figure 4186 shows the layout of surface equipment for a typical air drilling
operation. Described below are specialized surface components unique to air
drilling operations.
Blooey Line. This special pipeline carries exhaust air and cuttings from the
annulus to the flare pit. The length of the blooey line should be sufficient to
keep dust exhaust from interfering with rig operations. The blooey line should
have no constrictions or curved joints.
Bleed-Off Line. This line bleeds off pressure within the standpipe, rotary base,
kelly and the drill pipe to the depth of the top float valve. The bleed-off line
allows air (or gas) under pressure to be fed directly to the blooey line.
Air (or Gas) Jets. The jets are often used when there is the possibility that
relatively large amounts of natural gas may enter the annulus from a producing
formation as the drilling operation progresses. The air (or gas) jets pull a
vacuum on the blooey line and therefore on the annulus, thereby keeping gases
in the annulus moving out of the blooey line.
Compressors and Boosters. In a typical air drilling operation the compressors
supply compressed air from the atmosphere for discharge to the standpipe or
for the boosters. For air drilling operations, these primary compressors are
usually multistage machines that compress atmospheric air to about 200-300
psig. Air drilling operations require a fixed volumetric rate of flow, thus
compressors are usually rated by the capacity at sea level conditions, or the
actual cubic feet per minute of higher altitude atmospheric air they will operate
with. In addition, these primary compressors are also rated by the maximum
output air pressure. This is somewhat confusing since some of the primary
compressors used in the field are fixed ratio screw-type compressors. These
primary compressors produce only their maximum or fixed output pressure.