Page 163 - Air and Gas Drilling Manual

(,116
1
) ( . )
γ
67
γ g g = (53 2 .36 ) (519 3 0 . ) Chapter 5: Shallow Well Drilling Applications 5-5
.
= 0 0763 lb/ft
To determine the minimum volumetric flow rate of air at API standard
conditions, it is necessary to select (by trial and error) a volumetric flow rate, q g, that
3
will give a kinetic energy per unit volume of 3.0 ft-lb/ft in the annulus at the
bottom of the 1,000 ft borehole. Kinetic energy per unit volume should be a
minimum at the bottom of the annulus. The volumetric flow rate selected (trial and
error) is (at API standard conditions)
.
q g = 320 9 scfm
The value of Q g is
q g
Q g =
60
3
Q g = 535 ft /sec
.
The weight rate of flow of the gas, ˙ w , is
g
˙ w = γ Q
g g g
( . )
˙ w g = . 0 0763 5 35
˙ w = . 0 408 lb/sec
g
The borehole diameter, D h, is
d h = 450 inches
.
d h
D =
h
12
D = 0 375. ft
h
The estimated drilling rate of penetrations is 30 ft/hr. The weight rate of flow
of the solid rock cuttings, ˙ w , in the annulus is
s