Page 238 - Petrophysics 2E

FORMATION RESISTMTY FACTOR 21 1

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Equation for HCa (C, 1OOK)
1 M =3.446~10-’ +9.121x104C, -7.8434~1O-~Ck -5.16xlO4h(Cs)Cr
+ 3,4326C:
Equation for SO4 (C,< 140K)
M= 1
1.22235+6.6xlO-’C~:
Equation for K (C, SlOOK)
3 ( : : * I
M =8.61x10-’ +7.26177xlO-’[h(C,)~ +2.6376x104 - -8.558xlO-’C;:
Equation for C03
1,573$
M = -9.306~10-I +4.24~10~’e-~~”~~~ ==lodc*
+
d
I
Equation for Ca (C, < 275K) I
5
M = 1.026-9.7454~10-~C, -2.675~10-~~(C~)~ +1.255~10~’(~)
Cs
+ 1.8266~10-’ h(C, )
Equation for Mg (C, 5 2OOK)
M = 2.06566 - 1.6307xlO-’C~ - 8.2966~10” b(C,)p
7 For Na and Cl, M = 1 for any value of CS
8 For Br, M = 0.44 for any value of Cst

9 For NOS M = 0.55 for any value of Ca

The resistivity of the brine at 150’F is obtained from Equation 4.8:

81.77
Rw150 = 0.153 ( 150 + 6.77) = 0.0797 0h-m

Equation 4.10 yields Rw150 = 0.08 for XH = 8.3.

Resistivity-Concentration Equations
Worthington et al. recommended that brine resistivity of reservoir
waters that are not pure NaCl solution should be measured in a well
equipped standard laboratory, using a calibrated resistivity cell [4].
However, the resistivity of an accurately prepared NaCl solution can be
determined by calculation from accurately measured masses or volumes
of components.
Using data in the literature, Worthington and colleagues obtained
several correlations for conversion between resistivity and concentration