Page 531 - Air and Gas Drilling Manual

10-56 Air and Gas Drilling Manual
mixbh
P
Q
P g a5 w ˙ g T T 5 g w ˙ w g Q w
Substituting the values of ˙ w , ˙ w , P g, P a5, T g, T 5, Q g, and Q w into the above
w
g
equation gives, the specific weight of the aerated fluid mixture at the bottom of the
annulus is
1 821 14 60
.
.
mixbh
,
1 826 6 604 41
.
.
.
.
( 27 64) 0 234
160 728 519 67
,
.
27 4 lb/ft 3
.
mixbh
Using Equation 6-93, the pressure change in the aerated fluid through the drill bit,
∋ P b, can be approximated by
2
1 821 14 60
.
.
∋ P b 2
.
(
2 32 2) ( 27 4) ( 0 81) 2 0 0406 4
.
.
.
4
∋ P 139 001 lb/ft 2
,
b
where the nozzle loss coefficient is taken to be 0.81 (see Chapter 6, Section 6.5).
Using Equation 6-95, the pressure in the aerated fluid just above the drill bit
inside the drill string, P i5, is
P i5 P a5 ∋ P b
Using the above equation, the pressure in the aerated fluid just above the drill bit
inside the drill string is
,
P i5 160 728 139 001
,
2
,
P i5 299 729 lb/ft abs
P i5
p i5
144
,
p i5 2 082 psia