Page 184 - Air and Gas Drilling Manual

5-26 Air and Gas Drilling Manual
The drill pipe outside diameter, D p, is
d ˙ w p s = . . 0 192 lb/sec
= 2 375 inches
d p
D p =
12
D = 0 198 ft
.
p
The metamorphic rock borehole wall absolute surface roughness is assumed to
be 0.005 ft (see Table 8-1). Using Equation 5-6, the average surface roughness for
the annulus becomes
π
π
   
0
(.005 )   (.396 ) 2 + (.0 00015 )   (.198 ) 2
0
0
e = 4 4
π
π
av
  2 +   2
  (. 0 396 )   (. 0 198 )
4
4
.
e av = 0 0040 ft
Equation 5-5 becomes
  2
 
f =   1   
.
.

2 log  0 396 − 0 198  + 114 
.
   0 0040   
.
f = 0 049
.
Equations 5-2 and 5-3 become, respectively,
a a =  10.    1 +  0 192.   


 53 36.   0 840. 
a a = 0 023
.
0 840)
.
b = 0 049  53 36.  2 (. 2
a  2
π
.
(
2 32 2) ( 0 396 − 0 198. )  10.   [ 2 2 ] 2
.
0 396)
  (. − 0 198(. )
4