Page 369 - Air and Gas Drilling Manual

8-52 Air and Gas Drilling Manual
Thus, Figure 8-8 shows only one curve indicating the injection pressure is the same
as the pressure output of the compressor units.
In Illustrative Example 8.3b it was found that the actual shaft horsepower
required by each of the two reciprocating piston compressor units to compress air to
212.4 psia was approximately 249.9 (at 10,000 ft of depth). Also in Illustrative
Example 8.8c the derated horsepower available from the Caterpillar Model D398
prime mover at the surface elevation of 4,000 ft was found to be 684. Drilling at a
depth of 10,000 ft, the prime mover power ratio is
PR = 249 9 . ( 100) = 36 5 .
684 0 .
Figure 4-17 does not give data for power ratios less than 50 percent so a diesel fuel
consumption rate 0.700 lb/hp-hr will be assumed for power levels below 40 percent.
The total weight rate of diesel fuel consumption per hour is
˙ w = . 0 700 (249 . ) =9 174 .9 lb/hr
f

The diesel fuel consumption rate (in United States gallons) for the drilling depth of
10,000 ft is

q f = 174 9 . = 25 7 . gal/hr
(. )( .
0 8156 8 33)
Using the data in Figure 8-8 and similar calculations as those given above, the
diesel fuel consumption rate as a function of drilling time (or drilling depth) can be
obtained. Figure 8-9 shows the diesel fuel consumption rate as a function of drilling
time (or drilling depth) for each of the two reciprocating piston compressor units.
The approximate total diesel fuel needed for each compressor unit is obtained by the
integration of the area under the curve in Figure 8-9. This is approximately 1,257
gallons. It is standard practice to assume a 20 percent additional volume of fuel for
blowing the hole between connections and other compressor operations on the drill
rig. Therefore, the approximate diesel fuel needed for each compressor unit is 1,509
gallons. Therefore, the total diesel fuel needed at the drilling location for
compressor operations is approximately 3,018 gallons.
Illustrative Examples 8.2, 8.3a, 8.3b, and 8.3c demonstrate the calculation
procedures (step Nos. 1 to 10 given in Section 8.1) used to plan a typical deep oil or
natural gas well drilling operation.
Illustrative Example 8.4 In Illustrative Examples 8.3a, 8.3b, and 8.3c the
semi-trailer mounted unit with the Dresser Clark CFB-4, four-stage, reciprocating
piston compressor system was selected for the example drilling operation described
in that series of examples. In this illustrative example the drilling problem in the
Illustrative Example 8.3 series is to be solved using another candidate compressor
system unit. This compressor system unit is the semi-trailer mounted unit with
both the rotary primary and the reciprocating booster compressors driven by one