Capillary Pressure Models
The capillary pressure can be a user defined expression, or it can be derived from van Genuchten (
Ref. 2
) or Brooks and Corey (
Ref. 3
) models.
For van Genuchten model, the expression for the capillary pressure as a function of saturation follows the curve
(4-33)
where
p
ec
is the entry capillary pressure and
m
is a constitutive exponent.
For the Brooks and Corey model, the capillary pressure curve depends on saturation as
(4-34)
where
λ
is the pore distribution index.
When capillary pressure is selected as capillary model, the relative permeabilities are also determined by the van Genuchten or Brooks and Corey models. For the van Genuchten model, the relative permeabilities are given by
where
m
vG
and
l
vG
are constitutive constants.
For the Brooks and Corey model, the relative permeabilities are given by
where
λ
is again the pore distribution index.
