Page 515 - Air and Gas Drilling Manual

10-40 Air and Gas Drilling Manual
Openhole Section of the Annulus (7,000 ft to 10,000 ft)
The third annulus section increment is denoted by the length H 3. The
temperature at the bottom of the length H 3 in the openhole annulus section (bottom
of the drill pipe body lumped geometry), T 3, is
.
T 3 T r 001 ( H 1 H 2 H )
3
.
T T 0 01 6 650 350 2 375)
,
(
,
3 r
.
T 3 598 16˚R
The average temperature of this openhole annulus section H 3 is
T 2 T 3
T
av3
2
.
T av3 586 29˚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 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
78 039) (
(, 1 0)
.
a3
.
( 53 36) ( 586 29)
.
2 495 lb/ft 3
.
a3
The volumetric flowrate of the gas as it exits this openhole annulus section is
w ˙ g
Q ga3
ga3
.
1 821
Q ga3
.
2 495
3
.
Q ga3 0 730 ft /sec
The foam quality as it exits this openhole annulus section is