Page 200 - Air and Gas Drilling Manual

5-42 Air and Gas Drilling Manual
π
π
 
0
(.005
0
)
0
 
 
4
4
=
e
π
π
 
 
av
+
(. 0 240
)
(. 0 521
 
  (.521 ) 2 ) 2 + (.0 00015 )   2 (.240 ) 2
4
4
.
e av = 0 0042 ft
Equation 5-5 becomes
  2
 
f =   1  
.
.
  0 521 − 0 240  
.
 2 log    + 114 

.
 0 0042 
.
f = 0 043
Equations 5-2 and 5-3 become, respectively,
a =  10 .   1 +  0 897.  
a    
.
 53 36   1 599. 
.
a = 0 029
a
and
1 599)
.
b a = 0 043  53 36.   2 2 (. 2
π
.
2 32 2) ( 0 521 − 0 240. )  10.   [ 2 2 ] 2
.
(
0 521)
(.
  (. − 0 240)
4
b = 617 6
.
a
The bottomhole temperature is determined from the surface geothermal
temperature rock formations at the surface, the geothermal gradient, and the depth of
the borehole. The geothermal temperature of the rock formations near the surface is
assumed to be represented by the temperatures given in Table 4-1 (also see Appendix
D). Thus, for a 4,000 ft surface location this temperature is assumed to be 44.7˚F.
For this example the geothermal gradient is approximated to be 0.01˚F/ft. Thus,
T bh, is
o
t r = 44 7 F
.