Page 438 - Air and Gas Drilling Manual

9-42 Air and Gas Drilling Manual
In order to obtain the approximate value of the Fanning friction factor for
Equation 6-74, it is necessary to estimate the Reynolds number and, thus, the flow
conditions in the openhole annulus section along H 3. This is accomplished by
determining the Reynolds number at the exit end of this annulus section and
assuming this Reynolds number approximates the flow conditions throughout the
annulus section.
Using Equation 4-11, the approximate specific weight of the gas as it exits this
openhole annulus section is determined from P a2. This is
( 291 298) ( 1 0)
,
.
ga3
( 53 36) ( 586 29)
.
.
.
931 lb/ft 3
ga3
Using Equation 1-2, the density of the gas as it exits this annulus section, ga3 , is
.
931
ga3
32 2
.
lb sec 2
.
0 289
ga3 4
ft
From Equation 9-7, the kinematic viscosity of the gas at this location, ga3 , is
.
0 000000251
ga3
.
0 289
ft 2
0 000000867
.
ga3
sec
The average kinematic viscosity of the mixture at this position, , is
ava3
.
.
.
( 1 282)( 0 000000867) ( 31 92)( 0 0002691)
.
ava3
.
1 282 31 92
.
2
.
0 000259 ft /sec
ava3
The approximate average velocity of the aerated drilling fluid as it exits this
annulus section, V a3, is