Page 456 - Air and Gas Drilling Manual

9-60 Air and Gas Drilling Manual
Substituting the values of H 1, H 2, H 3, and H 4 into the right side of Equation 6-82
gives
6 650 350 2 375 125
,
.
1 dh 125
,
,
6 650 350 2 375
As can be seen in the above, the right and left hand sides of Equation 6-82 yield the
same answer. This shows that the lower limit pressure is correct.
The third drill string section increment is denoted by the length H 3. The
temperature at the bottom of the drill pipe body lumped geometry in the openhole
section is
T 3 598 16.˚R
The average temperature of the drill pipe body lumped geometry along H 3 and, thus,
the temperature of the aerated fluid flow inside the this drill string length is
T 586 29.˚R
av3
In order to obtain the approximate value of the Fanning friction factor for
Equation 6-82, it is necessary to estimate the Reynolds number and, thus, the flow
conditions inside the drill pipe body lumped geometry along H 3. This is
accomplished by determining the Reynolds number at the entrance end of the inside
of this drill string section and assuming this Reynolds number approximates the
flow conditions throughout the inside this drill string section.
Using Equation 4-11, the approximate specific weight of the gas as it enters this
drill string section is determined from P i3. This is

,
( 565 157) ( 1 0)
.
gi3
( 53 36) ( 586 29)
.
.
3
.
18 07 lb/ft
gi3
Using Equation 1-2, the density of the gas as it enters this drill string section, gi3 ,
is
18 07
.
gi3
32 2
.
lb sec 2
0 561
.
gi3 4
ft
From Equation 9-7, the kinematic viscosity of the gas at this location, gi3 , is