BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
Figure 1-11
Flow Behavior for Power Law Fluids
Similar to the Bingham Plastic Model, the Power Law Model does not describe the behavior of
drilling fluids exactly. However, the Power Law constants n and K are used in hydraulic calculations
(Chapter 9) that provide a reasonable degree of accuracy.
Figure 1–12 compares the flow curve of a typical drilling fluid to the flow curves of Newtonian,
Bingham Plastic, and Power Law Models.
Figure 1-12
Drilling Fluid vs. Newtonian, Bingham, and Power Law Fluids
A typical drilling fluid exhibits a yield stress and is shear thinning. At high rates of shear, all models
represent a typical drilling fluid reasonably well. Differences between the models are most
pronounced at low rates of shear, typically the shear rate range most critical for hole cleaning and the
suspension of weight material.
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 1-17