Page 360 - Air and Gas Drilling Manual

.
Equations 6-67 and 6-68 become, respectively,
10 .
=
a f i4 = 0 017 Chapter 8: Air, Gas, and Unstable Foam Drilling 8-43
i4
.
53 36
a i4 = 0 019
.
and
.
2 635)
.
b i4 = 0 017   53 36  2 (. 2
2
π
.
(
232 2 . ) 10    5
0 292)
 4  (.
,
b i4 = 3 958
Equation 6-72 becomes
  2 0 019) ( 125)   05 .
(.
 (, 2 + ( , 598 79) 2 e  598 79 − 1 
.
33 010)
3 958) (
.
    

P i3 =   2 0 019) ( 125)  
(.
 598 79 
.
 e 
 
2
P = 33 050 lb/ft abs
,
i3
P i3
p i3 =
144
p = 229 5 psia
.
i3
The pressure given above is the flowing air pressure at the top of the lumped drill
pipe tool joint length inside the drill string in the openhole section of the borehole.
The third drill string section increment is denoted by the length H 3. The
temperature at the bottom of the drill pipe body lumped geometry length in the
openhole section is
T = 598 16 R
o
.
3
The average temperature of the drill pipe body lumped geometry length along H 3
and, thus, the temperature of the gas flow inside this drill string length is