Water Properties Reference Material
Subtopics:
Salinity
Salinity represents the amount of salt (NaCl) dissolved in a fixed volume of water measured in parts per million (ppm). Water within a reservoir is often salty, and this salt content (salinity) has a small effect on the fluid flow properties of the water.
Water Compressiblity (cw)
The compressibility of any substance is the change in volume per unit volume per unit change in pressure. Water compressibility is a source of energy for fluid flow in a reservoir. It has a significant effect only when there is no free gas present in the reservoir. The water compressibility is a component in the calculation of total compressibility (ct), which is the value used in the determination of skin, dimensionless time, and all material balance considerations in the fluid flow calculations.
The value of water compressibility can be obtained from laboratory Pressure, Volume, Temperature (PVT) measurements, or determined from correlations. The magnitude is approximately between 1.0 x 10-6 and 9.0 x 10-6. It is a weak function of pressure, temperature, and salinity.
Water Formation Volume Factor (Bw)
Water formation volume factor is defined as the ratio of the volume of water at reservoir (in-situ) conditions to that at stock tank (surface) conditions. This factor, is used to convert the flow rate of water (at stock tank conditions) to reservoir conditions.
Water formation volume factor can be measured in the laboratory, or determined from correlations. Under most conditions it has a value of approximately 1.0. It is a very weak function of pressure, temperature, and salinity.
Water Specific Gravity (g or gw)
Water specific gravity is defined as the density of the water divided by the density of water at standard conditions (62.3 lbm / ft3). Water contained in a reservoir is saline and usually has a specific gravity greater than 1.0.
Water specific gravity has no effect on calculated properties such as water compressibility (cw), formation volume factor (Bw), and viscosity (mw). It is used, however, in the wellbore pressure drop calculations when converting pressures from wellhead to sandface.
Water Viscosity (mw)
Water viscosity is a measure of the amount of resistance to flow the water has. Higher values indicate more resistance to flow. For water, the viscosity decreases with increasing temperature and increases with increasing pressure. Water viscosity is a very weak function of pressure. Water at room temperature is approximately equal to 1 cp. In a reservoir, it is typically between 0.5 to 1 cp. This is due to the higher temperature, salinity, and the solution gas content of the water (if it is gas saturated).