Page 507 - Air and Gas Drilling Manual

10-32 Air and Gas Drilling Manual
Cased Section of the Annulus (Surface to 7,000 ft)
The first annulus section increment is denoted by the length H 1. The
temperature at the bottom of the length H 1 in the cased annulus section (bottom of
the drill pipe body lumped geometry), T 1, is
.
T 1 T r 001 H 1
(
.
T T 0 01 6 650)
,
1 r
.
T 1 570 91˚R
The average temperature of this cased annulus section H 1 is
T r T 1
T
av1
2
T av1 537 66˚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 cased annulus section along H 1. 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 and starts into the Tee is determined from P Tee. This is
(, . ) ( .
7 303 1 1 0)
ga1
.
.
( 53 36) ( 537 66)
0 271 lb/ft 3
.
ga1
The volumetric flowrate of the gas as it exits this cased annulus section and starts
into the Tee is
w ˙ g
Q
ga1
ga1
.
1 821
Q
ga1
0 271
.
3
Q 671 ft /sec
.
ga1