Page 627 - Air and Gas Drilling Manual

Equation 6-72 becomes
05 .
(.
125)
2 0 019) (
2
.
598 79
65 830)
3 958) (
(, 2 ( , Chapter 11: Specialized Drilling Equipment 11-65
e
.
1
598 79)
P
i3 2 0 019) ( 125)
(.
.
e 598 79
2
,
P i3 65 660 lb/ft abs
P i3
p
i3
144
p i3 456 0 psia
.
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 3 598 16˚R
.
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
.
T av3 586 29˚R
The inside surface of the drill pipe body has the surface roughness of commercial
steel. Therefore, over this lumped drill pipe body length the surface roughness is
.
e 0 00015 ft
p
With the above, Equation 6-73 becomes
2
1
f i3 0 319
.
2 log 114
.
0 00015
.
f i3 0 016
.