Page 538 - Air and Gas Drilling Manual

The average kinematic viscosity of the mixture as it enters this drill string section,
, is
avi4
( 1 821)( 0 000000926) Chapter 10: Stable Foam drilling 10-63
(
.
.
14 60)(
.
0 00001078)
.
avi4
1 821 14 60
.
.
2
0 00000969 ft /sec
.
avi4
Using the inside diameter of the drill pipe tool joints, D 6, the approximate
average velocity of the aerated drilling fluid as it enters this drill string section, V i4,
is
.
,
1 826 6 . 598 79
.
( 27 64) 0 234
.
.
,
278 659 519 67
V i4
0 292 2
.
4
.
V i4 663 ft/sec
Using Equation 6-103, the Reynolds number of the aerated drilling fluid as it
enters this drill string section, N Ri4, is
(. ) ( .292 )
6
0
63
N
Ri4
. 0 00000969
,
N Ri4 199 492
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 6-106) is used to determine the approximate Fanning friction factor for the
aerated fluid flow inside this drill string section.
The inside surface of the drill pipe tool joints is commercial steel with the
surface roughness
e p 0 00015 ft
.
With the above, Equation 6-106 becomes
2
1
f i4 0 292
.
2 log 114
.
0 00015
.