Page 167 - Air and Gas Drilling Manual

144
p p bh = P bh . Chapter 5: Shallow Well Drilling Applications 5-9
= 26 3 psia
bh
This is the pressure at the bottom of the borehole in the annulus.
Using Equation 4-11, the specific weight of the air at bottomhole pressure and
temperature conditions is
1
3
(,792 ) ( . )
0
γ =
bh
67
(53 .36 ) (528 . )
γ = 0 136 lb/ft 3
.
bh
The volumetric flow rate of the gas at the bottom of the borehole in the annulus,
Q bh, is
0
35
5
(.0763 ) ( . )
Q bh =
. 0 136
3
.
Q bh = 3 007 ft /sec
The velocity of the gas at the bottom of the borehole in the annulus, V bh, is
.
V = 3 007
π
  [ 2 2 ]
bh
(.
0 375)
  (. − 0 198)
4
.
V = 37 7 ft/sec
bh
The kinetic energy per unit volume at the bottom of the borehole in the annulus,
KE bh, is (see Chapter 1 and Equations 1-1 and 1-2)
.
ρ = 0 136
bh
32 2
.
ρ = 0 00422 lb − sec 2
.
bh 4
ft
.
) 37 7 . )
KE bh = 1 (0 00422 ( 2
2