Page 529 - Air and Gas Drilling Manual

10-54 Air and Gas Drilling Manual
.
sfbh
.
0 365
.
0 610 0 365 0 234
.
sfbh
The lumped geometry analysis provides a methodology for determining the
approximate pressures in the annulus. These pressures can be used to determine the
kinetic energy per unit volume value using the actual drill pipe outside diameter at
the critical position just above the drill collars (where the kinetic energy per unit
volume should be a minimum).
The specific weight of the foam as it exits the openhole drill collar annulus
section was determined above to be
24 881 lb/ft 3
.
sfa5
The average velocity of the foam just above the drill collar annulus section as it
flows around the drill pipe body is
P at T av5
Q g Q w
P T
a4 at
V
sfake
D 2 h D 2 2
4
1 826 6 601 91
.
,
.
.
.
( 27 64) 0 234
137 281 519 67
,
.
V sfake
.
0 656 2 0 375 2
.
4
V sfake 290 ft/sec
.
Using Equation 1-2, the density of the foam at this position in the annulus is
sfa5
sfake
g
24 881
.
sfake
.
32 2
2
lb sec
.
0 773
sfake 4
ft