Page 457 - Air and Gas Drilling Manual

.
0 000000251
gi3
.
0 561
ft 2 Chapter 9: Aerated Fluid Drilling 9-61
.
0 000000447
gi3
sec
The average kinematic viscosity of the mixture as it enters this drill string section,
, is
avi3
.
.
.
.
( 1 282)( 0 000000447) ( 31 92)( 0 0002691)
avi3
.
.
1 282 31 92
2
0 000259 ft /sec
.
avi3
Using the inside diameter of the drill pipe tool body, D 7, the approximate
average velocity of the aerated drilling fluid as it enters this drill string section, V i3,
is
1 826 6 . 586 29
,
.
(. 0 426
19 47)
.
.
,
565 157 519 67
V i3
.
0 319 2
4
.
V i3 622 ft/sec
Using Equation 6-83, the Reynolds number of the aerated drilling fluid as it
enters this drill string section, N Ri3, is
6
(.22 ) ( .319 )
0
N
Ri3
. 0 000259
N Ri3 7 665
,
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 body is commercial steel with the surface
roughness
.
e p 0 00015 ft
With the above, Equation 6-86 becomes