PetroCalcHubFree
Reservoir EngineeringPermeability and Flow

Calculation of Fractional Flow Curve Formula

fw=11+μwkrokrwμof_w = \frac{1}{1 + \frac{\mu_w \cdot k_{ro}}{k_{rw} \cdot \mu_o}}

Calculation of Fractional Flow Curve calculates fraction of total flowing stream composed of water for permeability and flow workflows in reservoir engineering.

Calculate

How engineers use this formula

Use this formula when the listed inputs (mu_w, mu_o, k_rw, k_ro) are known and the assumptions behind the cited permeability and flow relationship match the engineering case being checked.

Assumptions

  • Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
  • The declared units match the field-unit constants used in the formula.
  • The cited formula applies to the selected petroleum engineering workflow.

Limitations

  • The calculation does not replace a full engineering model or operating procedure.
  • Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.

Common mistakes

  • Mixing unit systems without converting the inputs.
  • Using default example values as field recommendations.
  • Applying the formula outside the source assumptions.

Default example

Using the default inputs, f_w equals 0.681818 dimensionless.

mu_wcP

1

mu_ocP

5

k_rwdimensionless

0.3

k_rodimensionless

0.7

Inputs

mu_w

cP

Water Viscosity

mu_o

cP

Oil Viscosity

k_rw

dimensionless

Relative Permeability to Water

k_ro

dimensionless

Relative Permeability to Oil

Outputs

f_w

dimensionless

Fraction of Total Flowing Stream Composed of Water

mu_w

cP

Water Viscosity (rearranged)

mu_o

cP

Oil Viscosity (rearranged)

k_rw

dimensionless

Relative Permeability to Water (rearranged)

k_ro

dimensionless

Relative Permeability to Oil (rearranged)

Source and review

reviewed

Craig Jr. F. F. (2004). The Reservoir Engineering Aspects of Waterflooding, Vol. 3. SPE Monograph Series, Page: 112.

Source

Related formulas and calculators

Average Permeability for Linear Flow in Layered Beds
Permeability
Average Permeability for Linear Flow - Series Beds
Permeability
Average Permeability for Parallel-Layered Systems
Permeability
Average Permeability in Radial Systems
Permeability
Klinkenberg Apparent Gas Permeability
Permeability
Jones-Owens Klinkenberg Slip Factor
Permeability