Page 623 - Air and Gas Drilling Manual

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p p p ianp 219 2 Chapter 11: Specialized Drilling Equipment 11-61
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The critical pressure ratio for air is 0.528. The ratio of the pressure below the
turbine to the pressure above the turbine is less than the critical pressure ratio,
therefore, the flow conditions in the active nozzles are sonic.
Geometry Inside the Drill String
Starting at the bottom of the drill string, the total length of the drill collars
length increment, H 5, in the openhole section is
H 500 ft
5
The inside diameter of the drill collars length in this openhole section is
.
d 5 2 8125 inches
d 5
D
5
12
D 5 0 234 ft
.
The total length of the drill pipe tool joints lumped geometry increment, H 4, in
the openhole section is
H 4 125 ft

The inside diameter of the drill pipe tool joints lumped geometry in this openhole
section is

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d 6 350 inches
d 6
D 6
12
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D 6 0 292 ft
The total length of the lumped drill pipe body geometry increment, H 3, in the
openhole section is
H 2 375 ft
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3