Презентация на тему Introduction to effective permeability and relative permeability

medium saturated with a single fluid (e.g. Sw=1)
Absolute permeability

can be calculated from the steady-state flow equation (1D, Linear Flow; Darcy Units):

Review: Absolute Permeability

3 fluids
Water-oil systems
Oil-gas systems
Water-gas systems
Three phase systems (water, oil,

and gas)
To evaluate multiphase systems, must consider the effective and relative permeability

of a porous medium for one fluid phase when

the medium is saturated with more than one fluid.
The porous medium can have a distinct and measurable conductance to each phase present in the medium
Effective permeabilities: (ko, kg, kw)

Effective Permeability

Amyx, Bass, and Whiting, 1960; PETE 311 Notes

units):

qn = volumetric flow rate for a specific phase,

n

A = flow area
ΔΦn = flow potential drop for phase, n (including pressure, gravity and capillary pressure terms)
μn = fluid viscosity for phase n
L = flow length

Modified from NExT, 1999; Amyx, Bass, and Whiting, 1960; PETE 311 NOTES

permeability of a fluid at a given saturation to

some base permeability
Base permeability is typically defined as:
absolute permeability, k
air permeability, kair
effective permeability to non-wetting phase at irreducible wetting phase saturation [e.g. ko(Sw=Swi)]
because definition of base permeability varies, the definition used must always be:
confirmed before applying relative permeability data
noted along with tables and figures presenting relative permeability data

Relative Permeability

Amyx, Bass, and Whiting, 1960

=0.5
Sw =0.3



∴Sg = 0.2

Sor
Oil
Two-Phase Flow
Region
Irreducible
Water
Saturation
kro @ Swi

Residual Oil
Saturation
Wettability and direction of

saturation change must be considered
drainage
imbibition

Base used to normalize this
relative permeability curve is
kro @ Swi

As Sw increases, kro decreases
and krw increases until
reaching residual oil
saturation

Modified from NExT, 1999

Imbibition Relative Permeability
(Water Wet Case)

Permeability, Fraction
1.0
0.6
0.8


Water
Oil

Strongly Water-Wet Rock
Water flows more freely
Higher

residual oil saturation

Modified from NExT, 1999

pore size distribution
Wettability
Fluid saturation history (i.e., imbibition or

drainage)

Factors Affecting Relative Permeabilities

After Standing, 1975

for different rocks and fluids
Relative permeability affects the flow

characteristics of reservoir fluids.
Relative permeability affects the recovery efficiency of oil and/or gas.

Modified from NExT, 1999