Page 437 - Air and Gas Drilling Manual

.
,
p
a2
p
P
144
a2
,
P a2 2 022 9 psia 2 Chapter 9: Aerated Fluid Drilling 9-41
291 298 lb/ft abs
a2
Substituting the values of ˙ w , Q g, Q m, P g, P a1, P a2, T g, T av2, D 2, D 3, f a2, and g
t
into the left side of Equation 6-74 gives
,
! 291 298
#
# dP
# 2 350
# 39 190 3 . 0 426
,
.
# 34 15 0 021 P
.
.
∀ 268 632 1
,
39 190 3 .
,
.
.
.
0 426 747 % 0 668 2 0 552 2 &
.
P 4

Substituting the values of H 1 and H 2 into the right side of Equation 6-74 gives
6 650 350
,
1 dh 350
6 650
,
As can be seen in the above, the right and left hand sides of Equation 6-74 yield the
same answer. This shows that the upper limit pressure is correct.
Openhole Section of the Annulus (7,000 ft to 10,000 ft)
The third annulus section increment is denoted by the length H 3. The
temperature at the bottom of the length H 3 in the openhole annulus section of the
borehole (bottom of the drill pipe body lumped geometry), T 3, is
T 3 T r 001 ( H 1 H 2 H )
.
3
,
T 3 T r 0 01 6 650 350 2 375)
.
,
(
T 3 598 16.˚R
The average temperature of this openhole annulus section H 3 is
T 2 T 3
T av3
2
T av3 586 29.˚R