BAKER HUGHES - Drilling Fluids Reference Manual

HYDRAULICS
ρ = fluid density, lb m /gal
If γ p > γ b , the slip velocity is determined by the equation below, slip velocity of a particle in
turbulent flow.
Turbulent Flow Condition
Find the particle shear stress:
where:
τp
= 7.9 T( 20.8 – ρ)
τ p = particle shear stress, lb f /100 ft
2
T = particle thickness, in.
ρ = fluid density, lb m /gal.
Slip velocity of a particle in turbulent flow is:
where:
V s
16.62τp
= ------------------
ρ
V s = slip velocity, ft/min
τ f /100 ft 2
p = particle shear stress, lb
ρ = fluid density, lb m /gal
Cuttings Transport
The cuttings transport for each different hole geometry is obtained by subtracting the slip velocity
of the cuttings from the annular velocity in that particular section of the hole by:
where:
Vt
= V a − V s
V t = cuttings transport, ft/ min
V a = annular velocity × 60, ft/min
V s = slip velocity, ft/min
Transport Efficiency
Perhaps more important than an actual cuttings transport value is the cuttings transport
efficiency, which is simply the ratio of cuttings transport to annular velocity, defined by:
E t
V t
----- × 100 1 V s
= = ⎛ – ----- ⎞ × 100
⎝ ⎠
V a
V a
where,
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 9-26