Page 352 - Air and Gas Drilling Manual

Chapter 8: Air, Gas, and Unstable Foam Drilling 8-35
=
111 3 psia
p
.
a3
The fourth annulus seciton increment is denoted by the length H 4. The
temperature at the bottom of the length H 4 in the openhole annulus section (bottom
of the drill pipe tool joints lumped geometry), T 4, is
T = T + 001 ( H + H + H + H )
.
4 r 1 2 3 4
T = T + 0 01 9 500)
,
.
(
r
4
T = 599 41 R
o
.
4
The average temperature of this openhole annulus section H 4 is
T + T
T av4 = 3 4
2
o
.
T av4 = 598 79 R
Using Equation 8-2, the average absolute surface roughness of this annulus section,
e av4, is
π
π
   
0 552)
0 656)
0 00015)
001)
(.  4  (. 2 + (.  4  (. 2
e av4 =
π
π
  2 +   2
0 552)
0 656)
 4  (.  4  (.
.
e av4 = 0 0059 ft
Equation 6-58 becomes
  2
 
f a4 =   0 656 − 1 0 552   
2  log  . .  + .
114

   0 0059   
.
.
f a4 = 0 076
With the above values Equations 6-52 and 6-53 become, respectively,