Page 536 - Air and Gas Drilling Manual

Chapter 10: Stable Foam drilling 10-61
.
0 00015 ft
e
p
With the above, Equation 6-106 becomes
2
1
f i5
.
.
2 log 0 234 114
.
0 00015
.
f 0 018
i5
Equation 6-102 for the fifth increment inside the drill string can be solved for
the pressure at the top of the increment, P i4. This involves selecting this lower limit
by a trial and error procedure. The magnitude of the lower limit pressure on the left
side of the equation is selected to allow the left side integral to equal the right side
integral. The integration can be carried out on the computer using one of the
commercial analytic software programs. The trial and error magnitude of the lower
limit pressure is
,
.
p i4 1 935 1 psia
P i4 p 144
i4
2
P i4 278 659 lb/ft abs
,
Substituting the values of ˙ w , ˙ w , Q g, Q w, P g, P i4, P i5, T g, T av5, D 5, f i5, and g
g w
into the left side of Equation 6-102 gives
,
∃ 299 729
&
& dP
& 2 500
,
& 58 477 0 . 0 234 !
.
& 16 42 0 018 P
.
.
% 278 659 1 ∀
,
58 477 0 .
,
.
.
.
0 234 15 07 0 234 2
P 4
#
Substituting the values of H 1, H 2, H 3, H 4, and H 5 into the right side of Equation 6-
102 gives
,
6 650 350 2 375 125 500
.
1 dh 500
6 650 350 2 375 125
,
,