Page 499 - Air and Gas Drilling Manual

10-24 Air and Gas Drilling Manual
The length of the surface return flow line (between the Tee and the back pressure
valve), L , is
sr
L sr 100 0.ft
The absolute viscosity of the stable foam, sf , can be approximated by [4]
.
1 3 6 (10-5)
sf w
where is the foam quality at any position in the annulus.
Using Equation 10-5, the absolute viscosity of the foam just upstream of the
back pressure valve, , is
sfbp
(
.
.
.
0 00002089 1 3 6 0 98)
sfbp
lb sec
.
0 00009459
sfbp 2
ft
The specific weight of the foam just upstream of the back pressure valve, ,
sfbp
is approximated by
w ˙ t
sfbp
P at T r
Q g Q w
P bp T at
.
17 37
sfbp
.
.
,
1 826 6 504 41
( 27 64) 0 234
.
.
.
.
4 274 6 519 67
,
1 485 lb/ft 3
.
sfbp
From Equation 1-2, the density of the foam just upstream of the back pressure valve,
, is
sfbp
.
1 485
sfbp
32 2
.
lb sec 2
0 0461
.
sfbp 4
ft