Page 488 - Air and Gas Drilling Manual

.
D
p
The estimated drilling rate of penetration is 60 ft/hr. The weight rate of flow
of solids, ˙ w , from the advance of the drill bit is
s 0 375 ft Chapter 10: Stable Foam drilling 10-13
˙ w D 2 62 .4 S (10-2)
s h s
4 (60 ) (60 )
˙ w . 0 656 2 62 .4 . 2 7 60
s
4 60 60
˙ w . 0 949 lb/sec
s
Although the non-friction solution is less complex than the friction solution, it
is still necessary to use trial and error to obtain the value of the incompressible fluid
(in this example fresh water with surfactant) volumetric flow rate required to yield an
3
annulus bottomhole kinetic energy per unit volume of approximately 3.0 ft-lb/ft .
Also, the bottomhole foam quality must be greater than 0.60. Note that since the
surface foam quality is defined as 0.98, the volumetic fow rate of the compressible
gas (air) is defined when the incompressible fluid is defined.
It is assumed that the volumetric flow rate of water (with surfactant), q w, into
the top of the inside of the drill string is
q w 84 0 gal/min
.
The volumetric flow rate of water, Q w, in consistent units is
84 0 231
.
Q w 3
12 60
3
.
Q w 0 187 ft /sec
The specific weight of the incompressible fluid is

62 4 lb/ft 3
.
w
The weight rate of flow of the incompressible fluid is
˙ w Q
w w w
˙ w w (62 4 )
. ) ( . 0 187