PROPERTIES OF OILFIELD BRINES - Petroleum Reservoir Fluid Property Correlations - page 168

situation, the amount of methane dissolved in the brine is independent
of pressure, and the brine is said to be undersaturated . For this case, the
compressibility may be calculated as follows.

Step 13. First, calculate the derivative of the methane-free brine specific
volume with respect to pressure, from the methane-free compressibility
as given in equation (4.27).

(4.27)

,

where v b, 0 is the specific volume of methane-free brine from equation
(4.23), and c b, 0 is the compressibility of methane-free brine from
equation (4.9).

Step 14. Next, calculate the second derivatives with respect to pressure

for the terms , λ CH 4 ,Na , and ζ CH 4 ,NaCl , using equations (4.28)-(4.30),
along with the appropriate coefficients from table 4-11.

(4.28)

(4.29)

(4.30)