BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
Table 1-1 shows the corresponding shear rate in reciprocal seconds to the V-G meter speed in rpm,
with standard Rotor-Bob spring combination (R 1 -B 1 ).
Table 1-1
V-G Meter Speed and Corresponding Shear Rate
V-G Motor Speed
(rpm)
Shear Rate ( γ )
(Sec 1 )
3 5.11
6 10.2
100 170
200 341
300 511
600 1022
We define n a and K a as the Power Law constants for the low shear rate range and n p and K p as the
constants for the high shear rate range. From Figure 1–13, we find the slope (n a ) of the line between
the dial readings at 300 rpm and 3 rpm. Since the slope of a line is equal to the “rise over the run”
then,
( log θ 300 – logθ 3 )
n a = -------------------------------------------
log 511 – log 5.11
θ 300
θ 3
n a = 0.5log---------
K a may be obtained from Figure 1–12 by this equation.
logK a = ( logθ 300 – n a log511)
K a
θ300
= ------------
511 n a
In a like manner, n p and K p are obtained as follows:
n p
log θ600 – logθ300
= ------------------------------------------
log 1022 – log511
n p = 3.32 log⎛ θ600
---------
⎝ ⎠
⎞
θ 300
logK p = ( logθ 600 – n p log1022)
K p
θ600
= --------------
1022 n p
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 1-19