PROPERTIES OF OILFIELD BRINES - Petroleum Reservoir Fluid Property Correlations - page 181

Extrapolating beyond the range of experimental data
Two of the correlations, Phillips et al. (1980) and Mao-Duan (2009),
have the form given in equation (4.40).

(4.40)

,

where μ b ( T , p , m ) is the brine viscosity, μ w ( T , p ) is the viscosity of pure
water, and μ r ( T , m ) is the relative viscosity of the brine.
Note that the relative viscosity is independent of pressure. Thus, the
pressure dependence of brine viscosity is accounted for by the pressure
dependence of pure water viscosity.
Figure 4-25 shows a comparison of the relative viscosity for brine
as a function of temperature for several different values of salinity,
for the Phillips et al. (1980) correlation equation and the Mao-Duan
(2009) correlation equation. The Phillips et al. correlation equation
used some of the Semenyuk et al. data in developing their correlation.
While Mao-Duan did not use the Semenyuk data in developing their
correlation equation, they did test their correlation equation against
the Semenyuk data. Both correlation equations show very similar
performance, with the maximum difference slightly larger than 4%
at a temperature of 572ºF (300ºC) and a salinity of 22.6 wt% sodium
chloride (5 g-mol/kg H 2 O).
Thus, either the Mao-Duan (2009) correlation equation or the
Phillips et al. (1980) correlation equation for relative viscosity of brine
may be used, along with a suitable correlation equation for pure water
viscosity, to get reasonable estimates of brine viscosity for pressures
to 29,000 psia (200 MPa) and temperatures to 572ºF (300ºC). The
Mao-Duan (2009) correlation equation for pure water, used with
either the modified Spivey et al. correlation equation or the IAPWS-
IF97 correlation equation for density of pure water, gives estimates of
pure water viscosity within 0.5% of those given by the IAPWS-08 pure
water viscosity correlation equation for pressures up to 14,500 psia (100
MPa) and temperatures from 50ºF to 572ºF (10ºC to 300ºC). It gives
estimates within 2% for pressures from 14,500 to 29,000 psia (100 to
200 MPa) and temperatures from 140ºF to 572ºF (60ºC to 300ºC).
The Spivey et al. method (2004) gives viscosities that are as much as
25% lower than those estimated from the Phillips et al. and Mao-Duan
equations, and is no longer recommended.