Page 154 - Air and Gas Drilling Manual

4-40 Air and Gas Drilling Manual

Figure 4-24: Semi-trailer mounted rotary primary and reciprocating booster compressor
system unit (courtesy of MI Air Drilling).
4.7.4 Four-Stage Reciprocating Compressor System
The compressor system unit shown in Figure 4-25 is another unusual design.
This is a semi-trailer mounted unit. The compressor is a large Dresser Clark CFB-4,
four-stage reciprocating piston compressor. The compressor is operated at a rotating
speed of 900 rpm. At this speed the compressor produces a volumetric flow rate of
1,200 scfm and a continuous maximum pressure of 1,000 psig (at API Mechanical
Equipment Standards standard conditions). The compressor can produce a
maximum pressure of 1,200 psig in intermittent service. Technically this
compressor system is a primary compressor system unit, but in application the unit
performs as a combined primary-booster all in one compressor system.
This compressor system is probably one of the most reliable system in the
drilling industry. These compressor systems were introduced in the early 1980’s to
provide compressed air for deep steam production wells in the Geysers geothermal
fields of Northern California. This application required the drilling of 11 inch
diameter wells to depths in excess of 10,000 ft. During the drilling of these wells,
steam inflow to the wells were nearly always encounter which would greatly
increases the injection pressure requirements. No similar air drilling requirements
have been encountered in the drilling of deep oil and natural gas wells. Not only do
these compressor systems produce a very useful volumetric flow rate, but they can
produce this volumetric flow rate at a great variety of pressures (i.e., from 100 psig
to 1,200 psig). Since these units are reciprocating piston compressors, the
volumetric flow rate is not affected by the pressure output. This compressor system
is presently the highest quality unit in the market and should be considered for any
critical or risky air drilling operation.
The compressor is directly coupled to a Caterpillar Model D398 prime mover.
The Caterpillar Model D398 is a V-12 piston configuration. The prime mover is
diesel fueled, turbocharged and aftercooled. At the rotation speed of 900 rpm, the
prime mover can produce a peak of 760 horsepower.