Page 211 - Air and Gas Drilling Manual

Chapter 5: Shallow Well Drilling Applications 5-53

Figure 5-13: Diesel fuel consumption rate as a function of drilling time for reciprocating
piston compressor of Illustrative Example 5.2c.
Comparing the diesel fuel consumption results from the rotary screw compressor
candidate and from the reciprocating piston compressor candidate it is seen that the
stand alone reciprocating piston compressor unit requires less than half the total
diesel fuel required by the rotary screw compressor (i.e., 330 gallons as opposed to
873 gallons). It should be noted that the prime mover for the rotary screw
compressor is also being used to provide power for the hydraulic pump for the rotary
top drive system. However, the power for this top drive is only about 13 percent of
the total power needed from the prime mover. The main reason for this high diesel
fuel consumption by the rotary screw compressor is the fact that its pressure output
is constant through the drilling time (and depth).
These example calculations illustrate one of the principal advantage of the
reciprocating piston compressor over the screw compressor. Unfortunately most
single drilling rigs are usually equipped with on-board rotary compressors. This is
due to the fact that rotary compressors are less bulky and have a small surface area