Page 138 - Air and gas Drilling Field Guide 3rd Edition

5.6 Prime Mover Input Power Requirements 129

11.5
68.0

66.0
11.0 64.0
Fuel Consumption (lb/hp-hr) 10.5 62.0 Fuel Consumption (N/kW-hr)

60.0
10.0

9.5 58.0
56.0

54.0
9.0
50 60 70 80 90 100
Percent Load on Prime Mover

FIGURE 5-17. Fuel consumption for natural gas [3, 12].

(a) Surface location at sea level (USCS units)
The prime mover has a maximum 350 hp available at 1800 rpm at sea level con-
ditions. The actual shaft power needed by the two-stage reciprocating compres-
sor to match the back pressure of 150 psig is 198.3 hp. Thus, the percent load
on the prime mover, or power ratio PR is
198:3
PR ¼ ð100Þ¼ 56:7:
350
Entering the abscissa of Figure 5-16 with the power ratio percent, the approxi-
mate fuel consumption rate can be read on the ordinate using the diesel
fuel curve. The approximate fuel consumption rate at this power level is
0.585 lb/hp-hr. The total weight of diesel fuel consumption per hour _ w f is
_ w f ¼ 0:585ð198:3Þ¼ 116:0lb=hr:

The specific gravity of diesel fuel is 0.8156 at 60 F [5]. The total volume (in U.S.
gallons) of diesel fuel consumption per hour q f is
116:0
q f ¼ ¼ 17:1 gal=hr;
ð0:8156Þð8:33Þ
where the specific weight of fresh water is 8.33 lb/gal.