Page 54 - Air and Gas Drilling Manual

2-4 Air and Gas Drilling Manual
Note that Figure 2-1 shows a drilling location that is oriented so that the blooey
line exit is downwind of the prevailing wind over the site. This keeps dust or
smoke from blowing across the location.
2.2 Flow Line to the Rig
The flow line to the standpipe of the drilling rig acts as a manifold collecting
the compressed air outputs from the primaries. These flow lines are API 2 7/8 inch
(OD), or 3 1/2 inch (OD) steel line pipe (or ASME equivalent) [5]. The valves in
the flow line at the booster compressor allow the air flow from the primaries to be
diverted to the booster when high compression of the air is needed. When higher
compression is not needed the booster compressor is isolated with the check valves
in the flow line to the rig.
2.2.1 Bleed-Off Line
The bleed-off line allows pressure to be released throughout the flow line to the
rig and inside the standpipe, rotary hose, kelly, and the drill pipe to the depth of the
first float valve (see Figure 2-1). The bleed-off line is usually run to the blooey line
and exits into that line. The bleed-off line is generally used when drill pipe
connections are made, replacing the drill bit (making round trips), and for other
operations where the well is opened to the atmosphere.
2.2.2 Scrubber
The scrubber removes excess water in the compressed air flow in the flow line.
If the humidity of the atmospheric air is high, then as the air is compressed in the
compressors much of the water will return to the liquid state. Dry air drilling
operations require the removal of this water before the compressed air is injected into
the well. The scubber is incorporated into a surge tank. The water in the
compressed air flow is collected in the bottom of the surge tank as the air flows
through this tank and is vented from time to time to eliminate the water from the
line.

2.2.3 Water Injection Pump
Unstable foam (mist) drilling operations require the injection of water into the
compressed air flow before the air is injected into the well. The water injection
pump injects water, chemical corrosion inhibitors, and liquid foamers into the
compressed air flow line. Figure 2-2 shows a skid mounted water injection pump
for air and gas drilling operations. These skid mounted water injection pumps are
used for the deep drilling operations. These pumps are capable of injecting up to 20
bbl/hr (at 42 gal/bbl) into the air or gas flow to the well.
The smaller drilling rigs have on-board water injection pumps. These smaller
rig water injection pumps have capabilities from 10 to 25 gal/min. The small water
injection pump carries out the same objective on these smaller rigs as the skid
mounted water pump for the larger double and triple drilling rigs. The injection of
water and appropriate chemicals and foamer is a vital option for air and gas drilling
operations. Very few air and gas drilling operations are carried out without some
water, chemical additives, and foam producing additives being injected.