BAKER HUGHES - Drilling Fluids Reference Manual

HYDRAULICS
Transitional flow in annulus,
⎡Rea
−
f
a
= ⎢
⎣
where:
( 3470 −1370n
)
800
a
⎤
⎥
⎦
×
⎡
⎢
⎣
a
b
( 4270 −1370n
) 3470 −1370n
a
3470 −1370n
a
a
−
24
⎤
⎥ +
⎦
24
log n
a =
50
a +
3.93
1.75−
log n
b =
7
a
Turbulent flow in annulus,
f a
=
------------
a
b
Re a
where:
a =
n a
log + 3.93
----------------------------- and b =
50
Friction-Loss Pressure Gradient
1.75 – logn ----------------------------- a
7
The total pressure required to circulate the drilling fluid includes not only the pressure drop across
the bit nozzles, but also the friction losses throughout the surface system, drillstring, and annular
sections. The appropriate friction factor (from previous section) is substituted into the Fanning
equation to determine the friction-loss pressure gradient. The appropriate values must be used for
each section of pipe or annulus sections with different diameters.
Friction-Loss gradient in pipe:
where:
P
------ p
L m
=
2
( f p ) ( V p ) ( ρ)
----------------------------------
25.81D
P p
L m
------ = pressure loss per measured depth, psi / ft
and,
f p = friction factor (laminar, transitional, or turbulent)
V p = bulk velocity in pipe, ft/sec
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 9-15