Page 191 - Air and Gas Drilling Manual

Chapter 5: Shallow Well Drilling Applications 5-33
inside of the drill string, and then the injection pressure (upstream through the
circulation system). In these calculations, the actual volumetric flow rate into the
compressor from the atmosphere is 700 acfm. Also, in these calculations, the actual
atmospheric conditions at the drilling location will be used (i.e., 11.769 psia and
70˚F) (see Table 4.2 or Appendix D). The atmospheric pressure of the air, P at,
entering the compressor is
.
p at = 11 769 psia
P at = p 144
at
2
P = 1 695 lb/ft abs
,
at
The atmospheric temperature of the air, T at, entering the compressor is
o
t at = 70 F
T at = t at + 459 67
.
o
.
T = 529 67 R
at
Thus, P g and T g become
P = P = 1 695 lb/ft abs
2
,
g at
T = T = 529 67 R
o
.
g at
Using Equation 4-11, the specific weight of the gas entering the compressor is
(1 695, ) (1 0. )
γ =
g
(53 36. ) (529 67. )
γ g = 0 0600 lb/ft 3
.
The volumetric flow rate of air entering the compressor, Q g, is

Q g = 700
60

3
Q g = 11 7 ft /sec
.