Reservoir EngineeringPVT and Rock-Fluid Properties
Capillary Number Formula
Capillary Number calculates capillary number for pvt and rock-fluid properties workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (mu_w, V, sigma_ow) are known and the assumptions behind the cited pvt and rock-fluid properties 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, N_c equals 0.000001 dimensionless.
mu_wcP
1
Vft/day
10
sigma_owdyn/cm
30
Inputs
mu_w
cPViscosity of Displacing Fluid
V
ft/dayCharacteristic Velocity
sigma_ow
dyn/cmInterfacial Tension between Oil and Water
Outputs
N_c
dimensionless
Capillary Number
mu_w
cP
Viscosity of Displacing Fluid (rearranged)
V
ft/day
Characteristic Velocity (rearranged)
sigma_ow
dyn/cm
Interfacial Tension (rearranged)
Source and review
reviewedLake, L. W. (1989). Enhanced Oil Recovery. Prentice Hall, Chapter 4.
Source