# Water compressibility

## Water compressibility

The formation water (brine) isothermal compressibility data is published in 1990 by McCain[1].

Water compressibility data [1]

## Math and Physics

At pressures above bubble point:

$c_w = 1 / (7.033 P + 0.5415 C_{mg/l} - 537 T + 403300)$[2]

## Application range

The correlation is valid only for temperatures between 200 and 270F, pressures of 1000 to 20000 psia, and salinities up to 200000 mg/l[2].

## Discussion

We, at pengtools.com, are calculating water compressibility below the bubble point with the same equation at the moment.

## Example. Calculating water isothermal compressibility

Water compressibility correlation in the PVT software at pengtools.com

Example source [1]

### Input data

$C_{mg/l} = 74289.3$

Calculate water isothermal compressibility at 3500 psia and 165°F?

### Solution

$c_w = 2.6348E-6\ psia^{-1}$

The solution is also available in the PVT software model at [The solution is available in the PVT calculator software model at www.pengtools.com

## Nomenclature

$C_{mg/l}$ = pressure correction, res bbl/STB
$C_{mg/l}$ = water salinity or solids concentration, mg/l
$P$ = pressure, psia
$T$ = Temperature, °F

Water bubble point pressure
Water compressibility
Water density
Water formation volume factor
Water salinity from density equation
Water solids concentration
Water viscosity
Gas/Water Interfacial Tension

## References

1. McCain, W.D. Jr. (1990). Properties of Petroleum Fluids (2 ed.). Oklahoma: PennWell Corp. ISBN 978-0878143351.
2. McCain, W.D. Jr. (1991). . Society of Petroleum Engineers (SPE-18571-PA).