BAKER HUGHES - Drilling Fluids Reference Manual

HYDRAULICS
Figure 9 - 6 Application of Power Law for 2.5 lb/bbl Xanthan Gum in 3% KCl Using
Data from 1022 and 511 sec -1
This example illustrates the need to apply this model within the power law region of a particular
fluid to assure accurate predictions of viscosity.
Bingham Plastic Model
The other two parameter model which has been widely used in drilling fluid applications is the
Bingham Plastic model (Equation 3). Fluids that exhibit Bingham Plastic behavior are
characterized by a yield point (τ 0 ) and a plastic viscosity (μ p ) that is independent of the shear rate
(Figure 9-7).
τ = τ 0 + μ p γ& ……………………………………………………………… (3)
where:
τ = Shear stress
τ 0 = Yield point
μ p = Plastic viscosity
γ& = Shear rate
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 9-6