Page 537 - Air and Gas Drilling Manual

10-62 Air and Gas Drilling Manual
As can be seen in the above, the right and left hand sides of Equation 6-102 yield
the same answer. This shows that the lower limit pressure is correct.
The fourth drill string section increment is denoted by the length H 4. The
temperature at the bottom of the drill pipe tool joints lumped geometry in the
openhole section is
.
T 4 599 41˚R
The average temperature of the drill pipe tool joints lumped geometry along H 4 and,
thus, the temperature of the aerated fluid flow inside the drill string length is
T av4 598 79˚ R
.
In order to obtain the approximate value of the Fanning friction factor for
Equation 6-102, it is necessary to estimate the Reynolds number and, thus, the flow
conditions inside the drill pipe tool joints lumped geometry along H 4. 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 i4. This is
( 278 659) ( 1 0)
.
,
gi4
( 53 36) ( 598 79)
.
.
.
872 lb/ft 3
gi4
Using Equation 1-2, the density of the gas as it enters this drill string section, gi4 ,
is
.
872
gi4
.
32 2
lb sec 2
0 271
.
gi4 4
ft
From Equation 9-7, the kinematic viscosity of the gas at this location, , is
gi4
.
0 000000251
gi4
0 271
.
2
ft
.
0 000000926
gi4
sec