Page 615 - Air and Gas Drilling Manual

(,
.
29 448) (
a5
(
.
53 36) (
604 41)
.
3 1 0) Chapter 11: Specialized Drilling Equipment 11-53
.
0 913 lb/ft
a5
Equation 6-63 is used to determine the pressure inside the drill bit just above the
nozzles. The flow through nozzles is subsonic. Therefore, Equation 6-63 must be
used to determine the pressure upstream of bottomhole annulus pressure. Equation
6-63 becomes
. 14
. 2 635 2 . 04
. 0 00802
P iab (,448 ) 1
29
232 . ) 2 . 14 (,448 ) ( . 0 913 )
(
29
. 04
2
P iab 31 330 lb/ft abs
,
P iab
p iab
144
p iab 217 6 psia
.
Drive Shaft Passage
The pneumatic turbine motor drive shaft passage has an inside diameter of 1.50
inches and a length of 21.0 inches. Thus, the inside diameter of the drive shaft
passage, D sp, is
d sp 150 inches
.
d sp
D
sp
12
.
D 0 125 ft
sp
The length of the drive shaft passage, L , is
sp
.
l sp 21 0 inches
l sp
L sp
12