Page 196 - Air and Gas Drilling Manual

5-38 Air and Gas Drilling Manual
drill collar outside and inside diameters. Also, the calculations have ignored the
existence of a blooey line type structure (most shallow drilling operations do not
have blooey lines). These minor losses are not important for shallow drilling
operations. The above injection pressure is less than the capability of this
reciprocating piston compressor (i.e., 350 psig), therefore, the compressor is capable
of producing 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 6,000 ft surface elevation. The prime mover for
this compressor is a diesel fueled, turbocharged, Caterpillar Model D353 with a peak
output of 270 horsepower at 1,000 rpm (at API standard conditions).
˙
The theoretical shaft horsepower, W , required by the compressor is obtained
s
from Equation 4-35a. Equation 4-35a becomes
 (. ) 
04
1 4
11
2
() ( . ) (.769 ) (700 )   80 .7  ()( . )
4
21
˙
W = − 1 
s
04
(.) 229 .17   11 .769  
 
˙
W = 79 .6
s
The mechanical efficiency, ε , is
m
ε = 090
.
m
From Equation 4-37, the first stage compression ratio of this compressor is
r =  80 7 .  05 .
s
.
 11 769 
.
r = 262
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 ) (262 )14 . − 1  

.
.

.
v
  
ε v = 0 903
.
˙
From Equation 4-39, the actual shaft horsepower, W , required by the compressor is
as