Page 219 - Air and Gas Drilling Manual

Chapter 5: Shallow Well Drilling Applications 5-61
=
( ,
T
T + 0 01 1 000.
)
bh
r
T
.
= 528 67 R
bh
The average temperature of this borehole is
T + T
T av = r bh
2
.
T = 523 67 R
av
The drill pipe inside diameter, D i, is
d = 4 670. inches
i
d
D = i
i
12
D = 0 389. ft
i
The Fanning friction factor, f, of the inside of the drill pipe is determined from
the von Karman empirical relationship for turbulent flow conditions [1]. This
empirical relationship is
  2
 
 
f =  1  (5-15)
  D  
i
 2 log. 

+1 14

   e   
p
where e P is the absolute surface roughness for commercial pipe (ft).
Although this is assumed to be an openhole in the annulus, the cuttings in a
reverse circulation operations return to the surface through the inside of the drill
string (in this case through the inside of the drill pipe). The absolute surface
roughness of commercial pipe, e p, is given as 0.00015 ft [2]. Equation 5-15 becomes
  2
 
f =  1 
  0 389  
.
.
 2 log  + 114 
.
  0 00015 
f = 0 016
.