Page 501 - Air and Gas Drilling Manual

10-26 Air and Gas Drilling Manual
.
0 00015 ft
e
p
Using Equation 106, the Fanning friction factor, f , for flow inside the return flow
sr
line is
2
1
f sr 0 469
.
2 log 114
.
.
0 00015
.
f sr 0 015
Equation 10-4 for the surface return flow line increment can be solved for the
pressure at the entrance end of the line, P . This involves selecting this upper limit
sr
of the left side integral by a trial and error procedure. The magnitude of the upper
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 (e.g., MathCad).
The trial and error magnitude of the upper limit pressure is
.
p sr 31 98 psia
P p 144
sr sr
2
,
.
P sr 4 604 4 lb/ft abs
Substituting the values of L , ˙ w , Q g, Q m, P g, P bp, P , T g, T r, D , f , and
sr
t
sr
sr
sr
g into the left side of Equation 10-4 gives
,
∃ 4 604 4 .
&
& dP
& 2 100
,
& 49 004 7 . !
.
& 17 37 0 015 P 0 234
.
.
% 4 274 6 . 49 004 7 . ∀
,
,
.
0 234 30 20 (. 2
0 469)
.
P 4
#
Substituting the value of L into the right side of Equation 10-4 gives
sr
100
1 dh 100
0