The above image represents Water – Oil Ratio.

To compute for the water – oil ratio, six essential parameters are needed and these parameters are **(μ _{o})Oil Viscosity, (μ_{w})Water Viscosity, (k_{rw})Relative Permeability to Water, (k_{ro})Relative Permeability to Oil, (B_{w})Water Formation Volume Factor **and

**(B**

_{o})Oil Formation Volume Factor.The formula for calculating the water – oil ratio:

WOR = [^{krw }/_{ kro}] [^{μoBo }/ _{μwBw }]

Where;

WOR = Water Oil Ratio

μo = Oil Viscosity

μ_{w} = Water Viscosity

k_{rw} = Relative Permeability to Water

k_{ro} = Relative Permeability to Oil

B_{w} = Water Formation Volume Factor

B_{o} = Oil Formation Volume Factor

Let’s solve an example;

Find the water – oil ratio when the oil viscosity is 9, water viscosity is 11 with a relative permeability to water of 21, relative permeability to oil of 7 and a water formation volume factor of 14 with oil formation volume factor of 27.

This implies that;

μo = Oil Viscosity = 9

μ_{w} = Water Viscosity = 11

k_{rw} = Relative Permeability to Water = 21

k_{ro} = Relative Permeability to Oil = 7

B_{w} = Water Formation Volume Factor = 14

B_{o} = Oil Formation Volume Factor = 27

WOR = [^{krw }/_{ kro}] [^{μoBo }/ _{μwBw }]

WOR = [21/7] [9 x 27 /11 x 14]

WOR = [21/7] [243/154]

WOR = [21/7] [1.5779]

WOR = [3] [1.5779]

WOR = 4.73

Therefore, the **Water – Oil Ratio **is** 4.73.**