Page 240 - Air and Gas Drilling Manual

5-82 Air and Gas Drilling Manual
The volumetric flow rate of air entering the compressor, Q g, is
Q = 840
g
60
3
Q g = 14 0 ft /sec
.
The weight rate of flow of air through the well is
( . )
˙ w = . 0 0636 14 0
g
˙ w = . 0 890 lb/sec
g
The borehole diameter, D h, is
d h = 5 875 inches
.
d
D = h
h
12
D = 0 490. ft
h
Using Equation 5-4, the weight rate of flow of the solid rock cuttings in the annulus
is  
π
40
.) (. ) 
2
˙ w s =   (. 0 490 ) (62 4 2 8   (60 ) (60 )   
 
4
˙ w = . 0 365 lb/sec
s
The inside surface of the innertube of the dual wall pipe has a surface roughness of
commercial pipe which is e p = 0.00015 ft [1]. Equation 5-15 becomes
  2
 
f =   1  
.

.
2 log  0 198   + 114 
   0 00015   
.
f = 0 018
.
Equations 5-13 and 5-14 become, respectively,