Page 535 - Air and Gas Drilling Manual

10-60 Air and Gas Drilling Manual
2
lb sec
1 938
.
w
4
ft
From Equation 9-7, the kinematic viscosity of the incompressible, , is
w
.
0 00002089
w
.
1 938
ft 2
.
0 00001078
w
sec
The average kinematic viscosity of the mixture as it enters this drill collar
section, avi 5 , is
.
.
.
( 1 821)( 0 000000865) ( 14 60)( 0 00001078)
.
avi 5
1 821 14 60
.
.
2
.
0 00000968 ft /sec
avi 5
Using the inside diameter of the drill collars, D 5, the approximate average
velocity of the aerated drilling fluid as it enters this drill collar section, V i5, is
.
,
1 826 6 . 601 91
.
( 27 64) 0 234
.
.
,
299 729 519 67
V i5
0 234 2
.
4
.
V i5 994 ft/sec
Using Equation 6-103, the Reynolds number of the aerated drilling fluid as it
enters this drill collar section, N Ri5, is
(.94 ) ( .234 )
9
0
N
Ri5
. 0 00000968
N Ri5 240 763
,
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 drill collars.
The inside surface of the drill collars is commercial steel with the surface
roughness