Page 542 - Air and Gas Drilling Manual

commercial analytic software programs. The trial and error magnitude of the lower
limit pressure is
p i2 1 323 3 psia Chapter 10: Stable Foam drilling 10-67
,
.
P p 144
i2 i2
2
,
P i2 190 555 lb/ft abs
Substituting the values of ˙ w , ˙ w , Q g, Q m, P g, P i2, P i3, T g, T av3, D 7, f i3, and g
w
g
into the left side of Equation 6-102 gives
,
∃ 273 856
&
& dP
& 2 2 375
,
,
& 56 959 5 . !
.
& 16 42 0 016 P 0 234
.
.
% 190 555 56 959 5 . 1 ∀
,
,
.
0 234 20 54 0 319 2
.
.
P 4
#
Substituting the values of H 1, H 2, and H 3 into the right side of Equation 6-102 gives
,
,
6 650 350 2 375
1 dh 2 375
,
6 650 350
,
As can be seen in the above, the right and left hand sides of Equation 6-102 yield
the same answer. This shows that the lower limit pressure is correct.
Inside the Drill String (7,000 ft to Surface)
The second drill string section increment is denoted by the length H 2. The
temperature at the bottom of the drill pipe tool joints lumped geometry in the cased
section is
.
T 2 574 41˚R
The average temperature of the drill pipe tool joints lumped geometry along H 2 and,
thus, the temperature of the aerated fluid flow inside the this drill string length is
T av2 572 66˚R
.
In order to obtain the approximate value of the Fanning friction factor for
Equation 6-102, it is necessary to estimate the Reynolds number and, thus, the flow
conditions inside the drill pipe tool joints lumped geometry along H 2. This is
accomplished by determining the Reynolds number at the entrance end of the inside