BAKER HUGHES - Drilling Fluids Reference Manual

HYDRAULICS
Laminar Flow Condition
Find the boundary shear rate,
186
γ b = --------------
D c ρ
where,
γ b = boundary shear rate, sec -1
D c = particle diameter, in.
ρ = fluids density, lb m /gal
Find the shear stress developed by the particle:
τ = 7.9 T 20.8 –
p ( ρ)
where,
τ p = particle shear stress, lb f /100 ft 2
T = particle thickness, in.
ρ = fluid density, lb m /gal
Find the shear rate developed by the particle using the annular power law constants for the fluid:
1
⎛
γ p
= ------
τ p⎞ n ----
a
⎜ ⎟
⎝K a ⎠
where,
γ p = particle shear rate, sec -1
τ p = particle shear stress, lb f /100ft 2
n a = annular flow behavior index
K a = annular consistency factor, poise
If γ p < γ b
, the slip velocity is determined by:
(
V s = 1.22τ p ----------------------
γp) ( D c )
ρ
1/2
where,
V s = slip velocity, ft/min
τ p = particle shear stress, lb f /100 ft 2
γ
-1
p = particle shear rate, sec
D c = particle diameter, in.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 9-25