Page 327 - Air and Gas Drilling Manual

8-10 Air and Gas Drilling Manual
g
Q
= 26 48 ft /sec
Q g g = q 60 . 3
3
where Q g is the gas volumetric flow rate (ft /sec). The weight rate of flow of the gas,
˙ w , is
g
˙ w = γ Q
g g g
. )
˙ w = . 0 0763 (26 48
g
˙ w = . 2 019 lb/sec
g
where ˙ w is the weight rate of flow of the gas in the circulation system (lb/sec).
g
The borehole diameter is
d h = 7 875 inches
.
d
D = h
h
12
D = 0 656. ft
h
where d h is the inside diameter of the borehole (inches),
D h is the inside diameter of the borehole (ft).
The estimated drilling rate of penetration is 60 ft/hr. The weight rate of flow of
the solid rock cuttings, ˙ w , in the annulus is
s
π
2
˙ w s =   D (62 . ) 4 S    60 κ 60    (8-1)
 
s
h
( ) ( ) 
4

where κ is the drilling rate (ft/hr),
S s is the specific gravity of the solid rock cuttings.
Therefore, ˙ w is
s
π
2
.) (. ) 
˙ w =   (. 0 656 ) (62 4 2 7  60  
s     (60 ) (60 )  
4
˙ w = . 0 950 lb/sec
s