PROPERTIES OF OILFIELD BRINES - Petroleum Reservoir Fluid Property Correlations - page 161

Density and compressibility of methane-free brine

Step 1. First, calculate the density of pure water at the reference pressure
of 70 MPa, ρ w ( T , 70 MPa), in g/cm 3 , at the temperature of interest, T ,
using equation (4.1), along with the coefficients given in table 4-6.

Table 4-6. Coefficients for equation of state for pure water for use with equation (4.1)
a i ρ w ( T , 70 MPa) E w ( T ) F w ( T )

a 1

-0.127213 4.221 -11.403

a 2

0.645486 -3.478 29.932

a 3

1.03265 6.221 27.952

a 4

-0.070291 0.5182 0.20684

a 5

0.639589 -0.4405 0.3768

Next, calculate the values of the pure water compressibility
coefficients E w ( T ) and F w ( T ), from equation (4.1), with the coefficients
given in table 4-6. The coefficients in table 4-6 are the same as in the
original Spivey et al. correlations.

Density and compressibility of pure water. Calculate compressibility
and density for pure water at the temperature and pressure of interest.
Skip steps 2 and 3 if only properties for brine are required.

Step 2. Calculate the compressibility c w ( T , p ), in MPa -1 , of pure water at
temperature T and pressure p , from equation (4.2).

(4.2)

Step 3. Calculate the density of pure water at temperature T and
pressure p .
First, calculate the values of I w ( T , 70 MPa) and I w ( T , p ) from equations
(4.3) and (4.4).

(4.3)

(4.4)