Page 212 - Air and gas Drilling Field Guide 3rd Edition

8.4 Water Injection and Formation Water Influx 203

Pressure (psia)
100 150 200 250
−7000
−2200

−7500
Injection Pressure
−2400
−8000
Depth (ft) −8500 −2600 Depth (m)

−9000
Bottom Hole Pressure
−2800
−9500

−3000
−10000
80 100 120 140 160
Pressure (N/cm 2 abs)

FIGURE 8-9. Drilling ahead, bottom hole and injection pressures versus depth.

8.4 WATER INJECTION AND FORMATION WATER INFLUX
Water is injected into the volumetric flow rate of air (or other gases) flowing from
the compressors to the top of the inside of the drill string for the following three
important reasons.
1. Saturate the air or other drilling gas with water vapor at bottom hole annu-
lus pressure and temperature conditions.
2. Eliminate the stickiness of the small rock cuttings “flour” generated by the
advance of the drill bit.
3. Assist in the suppression of combustion of the mixture of produced hydro-
carbons and oxygen-rich air.
Figure 8-10 shows a typical “mist” pump and a typical stand-alone, skid-
mounted positive displacement duplex liquid pump driven with a Caterpillar
Model 3304 diesel-fueled, naturally aspirated, prime mover. This pump forces liq-
uid into the pressurized air flow line from the compressors to the standpipe on
the drill rig (see Figure 3-1).