Page 233 - Air and Gas Drilling Manual

2
2
1 366)
(.

.
.
 53 36
b =

i
2
π
 
(
2 322 . ) ( .
 10 .
4
0 389)
(.
 
4
b = 236 1 0 016 0389) Chapter 5: Shallow Well Drilling Applications 5-75
.
i
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 2,000 ft surface location this temperature is assumed to be 51.9˚F.
For this example the geothermal gradient is approximated to be 0.01˚F/ft. Thus, T bh
is
o
t = 51 9 F
.
r
T = t + 459 67.
r
r
T = 511 57. o R
r
T bh = T + 0 01 2 400. ( , )
r
o
T bh = 535 54 R
.
The average temperature of this borehole is
T + T
T av = r bh
2
o
T = 523 54 R
.
av
Equation 5-12 becomes
  2 (. 0 035 ) ( , 2 400 )  . 05
[

P =  ( , 1 967 ) 2 + 236 1 .54 ) 2 ] e 523 .54 − 236 1 .54 ) 2 
. (523
. (523
ai
  

2
P = 5 421 lb/ft abs
,
ai
P ai
p ai =
144