Page 232 - Air and Gas Drilling Manual

5-74 Air and Gas Drilling Manual
d
= 12 25 inches
h
D = d h .
h
12
D = 1 021. ft
h
Using Equation 5-4, the weight rate of flow of the solid rock cuttings in the annulus
is
π
. ) ( . ) 
2
˙ w =   (. 1 021 ) (62 4 2 7  30  
s     (60 ) (60 )  
4
˙ w s = . 1 149 lb/sec
The inside diameter of the drill pipe, D i, is
d = 4 670. inches
i
d
D = i
i
12
D = 0 389. ft
i
The return flow of the air with the entrained rock cuttings flows to the surface
through the inside of the drill string. The surface roughness of commercial pipe is e p
= 0.00015 ft [2]. Equation 5-15 becomes
  2
 
f =  1 
  0 389  
.
.
  2 log  0 00015  +114  
.
f = 0 016
.
Equations 5-13 and 5-14 become, respectively,

a =  10.    1 +  1 149.   
i
 53 36.    1 366.  
a = 0 035.
i

and