Page 220 - Air and Gas Drilling Manual

5-62 Air and Gas Drilling Manual
With the above values Equation 5-13 becomes
 10 .
a =


i
 0 601.
 53 36     1 +  300.    
.
a = 0 112.
i
and Equation 5-14 becomes
0 601)
.
.
b = 0 016  53 36  2 (. 2
i  2
π
2 322 . ) ( .  10 .   4
0389)
(
0 389)
  (.
4
b = 45 6
.
i
Equation 5-12 becomes
  2 (. 0 016 ) ( , 1 000 )   . 05
[
P ai =  ( , 2 116 ) 2 + 45 6 . ) 2 ] e 523 .67 − 45 6 . ) 2 
. (523 67
. (523 67
   
2
P ai = 3 686 lb/ft abs
,
P ai
p ai =
144
p ai = 25 6 psia
.
This is the pressure at the bottom of the inside of the drill string just above the drill
bit.
Using Equation 4-11, the specific weight of the air above the drill bit inside the
drill pipe can be obtained knowing the pressure and temperature at the bottom of the
inside of the drill pipe. The specific weight is
0
1
(,686 ) ( . )
3
γ =
ai
(53 .36 ) (528 . )
67
γ ai = 0 132 lb/ft 3
.
The volumetric flow rate of the gas above the drill bit inside the drill pipe, Q ai,
is