Fluid saturation is how much each fluid is present in pore spaces of a rock. This will affect the ability of each fluid flow through porous media. This is one of critical values for reservoir engineering since many engineering calculations need fluid saturation values.
Fluid saturation is expressed in terms of volume of fluid divided by total pore space.
Gas saturation (Sg) = Vg ÷ Vp
Oil saturation (So) = Vo ÷ Vp
Water saturation (Sw) = Vw ÷ Vp
Total saturation of fluid is equation to 1, therefore this can mathematically be expressed like this.
Sg + So + Sw = 1
Vg = volume of gas in pore space
Vo = volume of oil in pore space
Vw = volume of water in pore space
How To Measure Fluid Saturation
Two methods to determine fluid saturation are 1) core sample and 2) wireline logging. Core sample is a direct method because it is a physical measurement. However, wireline logging is an indirect method because the values are derived from mathematical models.
Fluid Saturation Video by SPE