Page 524 - Air and Gas Drilling Manual

Chapter 10: Stable Foam drilling 10-49
The fifth annulus section increment is denoted by the length H 5. The
temperature at the bottom of the length H 5 in the openhole annulus section (bottom
of the drill collar geometry), T 5, is
.
T 5 T r 001 ( H 1 H 2 H 3 H 4 H )
5
T T 0 01 6 650 350 2 375 125 500)
,
(
,
.
5 r
T 5 604 41˚R
.
The average temperature of this openhole annulus section H 5 is
T 4 T 5
T
av5
2
.
T av5 601 91˚R
In order to obtain the approximate value of the Fanning friction factor for
Equation 6-88, it is necessary to estimate the Reynolds number and, thus, the flow
conditions in the openhole annulus section along H 5. 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
cased annulus section is determined from P a4. This is
,
(
.
)
( 137 281 1 0)
a5
.
.
( 53 36) ( 601 91)
.
4 274 lb/ft 3
a5
The volumetric flowrate of the gas as it exits this openhole annulus section is
w ˙ g
Q ga5
ga5
.
1 821
Q ga5
.
4 274
3
.
Q ga5 0 426 ft /sec
The foam quality as it exits this openhole annulus section is