Page 426 - Air and Gas Drilling Manual

9-30 Air and Gas Drilling Manual
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 18 91 psia
P p 144
sr sr
2
,
P sr 2 723 3 lb/ft abs
.
Substituting the values of L , ˙ w , Q g, Q m, P g, P at, P , T g, T r, D , f , and
sr
sr
sr
sr
t
g into the left side of Equation 9-11 gives
,
! 2 723 3 .
#
# dP
# 2 100
# 34 519 6 .
,
.
# 34 15 0 015 P 0 426
.
.
∀ 1 826 6 . 34 519 6 .
,
,
.
0 469)
0 426 30 20 (. 2
.
P 4

Substituting the value of L into the right side of Equation 9-11 gives
sr
100
1 dh 100
0
The aerated drilling fluid flows from the top of the annulus into the entrance of
the surface return flow line. The friction flow loss of the turn and of the two valves
at the entrance of the surface return flow line must be included. The approximate
specific weight of the aerated drilling fluid just after it passes through the Tee and
the valves at the top of the annulus is determined using the above determined P .
sr
The approximate specific weight at the Tee, Tee, is
w ˙ t
Tee P g T
r
Q g Q m
P sr T g
Substituting the values of ˙ w , P g, P , T g, T r, Q g, and Q m into the above equation
sr
t
gives the specific weight just downstream of the Tee and valves. This is