Page 489 - Air and Gas Drilling Manual

10-14 Air and Gas Drilling Manual
˙ w
11
.68 lb/sec
w
The definition of foam quality given by Equation 6-87, can be evaluated at the
top of the annulus upstream from the back pressure valve. Equation 6-87 defined at
the top of the annulus (upstream from the back pressure valve) is
Q
gbp
bp (10-3)
Q Q
gbp w
Solving Equation 10-3 for Q gbp gives
bp
Q gbp Q w
1 bp
Substituting the values for bp and Q w gives
. 098
Q gbp (. 0 187 )
1 . 0 98

3
.
Q gbp 917 ft /sec
Using Equation 4-11 the specific weight of the gas (air) upstream of the back
pressure valve can be obtained. This is
1
4
(,275 ) ( .)
0
bp
41
(53 .36 ) (504 . )
.
0 159 lb/ft 3
bp
The weight rate of flow of gas, ˙ w , is
g
˙ w Q
g bp gbp
˙ w (. 0 159 ) ( . )
9 17
g
˙ w . 1 456 lb/sec
g
The volumetric flow rate of the gas at the surface location atmospheric conditions is