Page 513 - Air and Gas Drilling Manual

10-38 Air and Gas Drilling Manual
From Equation 9-7, the kinematic viscosity of the foam as it exits this cased
annulus section is
0 00007890
.
sfa2
.
0 498
2
ft
.
0 0001584
sfa2
sec
The average velocity of the foam as it exits this cased annulus section is
P at T av2
Q g Q w
P a1 T at
V sfa2
D 1 2 D 3 2
4
.
1 826 6 . 572 66
,
( 27 64) 0 234
.
.
.
.
70 502 519 67
V sfa2
0 668 2 0 552 2
.
.
4
V sfa2 920 ft/sec
.
Using Equation 6-89 the Reynolds number of the foam as it exits this cased
annulus section is
V sfa2 D 1 D 3
N Rsfa2
sfa2
9
(.20 ) ( .668 . 0 552 )
0
N Rsfa2
. 0 0001584
N Rsfa2 22 542
,
The Reynolds number calculation above is greater than 4,000. This indicates that
the flow condition is turbulent. Therefore, the empirical von Karman equation (i.e.,
Equation 6-92) must be used to determine the Fanning friction factor for the foam
flow in this annulus section.
Both annulus section surfaces are commercial steel with the surface roughness
.
e p 0 00015 ft