Page 460 - Air and Gas Drilling Manual

9-64 Air and Gas Drilling Manual
The average kinematic viscosity of the mixture as it enters this drill string section,
, is
avi2
.
.
.
.
avi2 ( 1 282)( 0 000000609) ( 31 92)( 0 0002691)
.
1 282 31 92
.
2
0 000259 ft /sec
.
avi2
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 i2,
is
.
,
1 826 6 . 572 66
.
(. 0 426
19 47)
405 216 519 67
,
.
V i2
0 292 2
.
4
.
V i2 782 ft/sec
Using Equation 6-83, the Reynolds number of the aerated drilling fluid as it
enters this drill string section, N Ri2, is
0
7
(.82 ) ( .292 )
N
Ri2
. 0 000259
N Ri2 8 813
,
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 6-86) 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 6-86 becomes
2
1
f
i2 0 292
.
2 log 114
.
0 00015
.