Page 239 - Petrophysics 2E

2 12 PETROPHYSICS: RESERVOIR ROCK PROPERTIES

TABLE 4.3
CONCENTRATION CORRELATION CONSTANTS FOR EQUATION 4.13

Range of Concentration of NaCl Solution,
Concentration
Correlation csrn (mow
Constant 1 ,000-4 to lo-' 0.09 to 1.1 1.0 to 5.35

a1 9.42203 x lo-' 9.33134 x lo-' 9.33292 x lo-'
a2 8.889 x lo-' 8.47181 x lo-' 8.45971 x lo-'
a3 -2.72398 x lop2 -1.04563 x lo-' -910632 x lo-'
a4 -2.25682 x lop3 -7.05334 x lop2 -2.27399 x lo-'
a5 1.46605 x -2.35562 x lop2 2.27456 x lo-'
ac 0 0 -3.81035 x lo-'

of NaCl solutions. For a given concentration of NaCl solution in mol&
Csm, the water resistivity at 25°C is:

where: X, = concentration correlation function.
Csm = concentration of NaCl solution, mom.
al, . . . , a6 = correlation constants.

Table 4.3 shows the value of the correlation constants for three
ranges of concentration: low4 < CSmlO-', 0.09 < C,, < 1.4, and 1.0 <
Csm < 5.35.
Arp's equation for calculating Rw at any reservoir temperature T in
degrees Celsius is:

(4.14)

If the concentration of NaCl solution is given in ppm, then it is
necessary to convert it to mol& in order to solve for the concentration
correlation function Xc and then Rw25. The conversion equation
between ppm and mol/L is [4] :

(4.15)