Page 366 - Air and Gas Drilling Manual

Chapter 8: Air, Gas, and Unstable Foam Drilling 8-49
The injection pressure of approximately 212 psia is less than the capability of
the selected four stage reciprocating piston compressor (i.e., 1,000 psig), therefore,
the compressor is capable of producing the above injection pressure (the maximum
pressure capability of a reciprocating piston compressor is not derated with surface
location elevation as long as the prime mover has the power necessary to produce the
required pressure).
The last criteria to check is whether the prime mover of this primary compressor
unit has the power to operate at the 4,000 ft surface elevation. The prime mover for
this compressor is a diesel fueled, turbocharged, Caterpillar Model D398 with a peak
output of 760 horsepower at 900 rpm (at API standard conditions) (see Section 4.7
˙
in Chapter 4). The theoretical shaft horsepower, W , required by each of the two
s
compressors is obtained from Equation 4-35a. Equation 4-35a becomes
 , 2 400 
04
(.685 )  (. ) 
12
4
. 
() ( . ) 4  2    212 4 ()( . ) 
1
4
41
˙
W = − 1
s
04
(.) 229 .17   12 .685  
 
˙
W = 207 .4
s
The mechanical efficiency, ε , is
m
ε m = 090
.
This is a four-stage reciprocating piston compressor. Therefore,
n = 4
s
The first stage compressor ratio is
1
r =  212 4 .  4
s 
.
 12 685
r = 202.
s
The volumetric efficiency (only for the reciprocating piston compressor), ε , is
v
determined from Equation 4-38. The compressor clearance volume ratio, c, is
assumed to be 0.06. Equation 4-38 becomes
  1 
ε = 096 1 − (006 ) (202 )14 . − 1  

.
.
.

v
  
ε v = 0 922
.