Relative Permeability Table Generation

NeqSim provides a dedicated module for generating relative permeability tables using industry-standard Corey and LET models. The generated tables can be exported in Eclipse-compatible keyword format (SWOF, SGOF, SOF3, SLGOF).

Overview

Package: neqsim.pvtsimulation.reservoirproperties.relpermeability

Key Classes:

Class Description
RelativePermeabilityGenerator Main generator for relative permeability tables
RelPermTableType Enum for table types: SWOF, SGOF, SOF3, SLGOF
RelPermModelFamily Enum for model families: COREY, LET

Supported Models

Corey Power-Law Model (1954)

The Corey model uses a single exponent per phase to define the relative permeability curve:

\[K_{rw} = K_{rw,max} \cdot S_{wn}^{n_w}\] \[K_{row} = K_{ro,max} \cdot (1 - S_{wn})^{n_o}\]

where $S_{wn}$ is the normalized water saturation:

\[S_{wn} = \frac{S_w - S_{wc}}{1 - S_{wc} - S_{orw}}\]

Parameters: Each phase requires one exponent ($n_o$, $n_w$, $n_g$). Typical values range from 1 to 6.

LET Three-Parameter Model (2005)

The LET model (Lomeland, Ebeltoft, Thomas) provides greater flexibility for matching laboratory core-flood data:

\[K_r = K_{r,max} \cdot \frac{S_n^L}{S_n^L + E \cdot (1 - S_n)^T}\]

Parameters: Each phase requires three parameters (L, E, T):

Saturation Endpoints

Parameter Symbol Description
swc $S_{wc}$ Connate (irreducible) water saturation
swcr $S_{wcr}$ Critical water saturation (onset of water flow)
sorw $S_{orw}$ Residual oil saturation to water
sorg $S_{org}$ Residual oil saturation to gas
sgcr $S_{gcr}$ Critical gas saturation

Supported Table Types

Type Eclipse Keyword Columns Use Case
SWOF SWOF Sw, Krw, Krow, Pcow Water-oil two-phase
SGOF SGOF Sg, Krg, Krog, Pcog Gas-oil two-phase
SOF3 SOF3 So, Krow, Krog Three-phase oil function
SLGOF SLGOF Sl, Krg, Krog, Pcog Liquid-gas function

Usage Examples

Water-Oil Corey Curves (Java)

RelativePermeabilityGenerator gen = new RelativePermeabilityGenerator();
gen.setTableType(RelPermTableType.SWOF);
gen.setModelFamily(RelPermModelFamily.COREY);
gen.setSwc(0.15);
gen.setSorw(0.20);
gen.setKroMax(1.0);
gen.setKrwMax(0.25);
gen.setNo(2.5);
gen.setNw(1.5);
gen.setRows(25);

Map<String, double[]> table = gen.generate();

double[] sw = table.get("Sw");
double[] krw = table.get("Krw");
double[] krow = table.get("Krow");

Gas-Oil LET Curves (Java)

RelativePermeabilityGenerator gen = new RelativePermeabilityGenerator();
gen.setTableType(RelPermTableType.SGOF);
gen.setModelFamily(RelPermModelFamily.LET);
gen.setSwc(0.20);
gen.setSorg(0.15);
gen.setKroMax(1.0);
gen.setKrgMax(1.0);
gen.setLog(2.5);
gen.setEog(1.25);
gen.setTog(1.75);
gen.setLg(1.2);
gen.setEg(1.5);
gen.setTg(2.0);
gen.setRows(25);

Map<String, double[]> table = gen.generate();

Export to Eclipse Format

RelativePermeabilityGenerator gen = new RelativePermeabilityGenerator();
gen.setTableType(RelPermTableType.SWOF);
gen.setSwc(0.15);
gen.setSorw(0.20);
gen.setNo(2.5);
gen.setNw(1.5);
gen.setRows(20);

String eclipseKeyword = gen.toEclipseKeyword();
// Output:
// SWOF
// -- Sw       Krw       Krow       Pcow
//    0.15000000  0.00000000  1.00000000  0.00000000
//    ...
// /

Python (via neqsim-python)

from neqsim import jneqsim

RelPermGenerator = jneqsim.pvtsimulation.reservoirproperties.relpermeability.RelativePermeabilityGenerator
RelPermTableType = jneqsim.pvtsimulation.reservoirproperties.relpermeability.RelPermTableType
RelPermModelFamily = jneqsim.pvtsimulation.reservoirproperties.relpermeability.RelPermModelFamily

gen = RelPermGenerator()
gen.setTableType(RelPermTableType.SWOF)
gen.setModelFamily(RelPermModelFamily.COREY)
gen.setSwc(0.15)
gen.setSorw(0.20)
gen.setKroMax(1.0)
gen.setKrwMax(0.25)
gen.setNo(2.5)
gen.setNw(1.5)
gen.setRows(25)

table = gen.generate()

# Plot results
import matplotlib.pyplot as plt
sw = list(table.get("Sw"))
krw = list(table.get("Krw"))
krow = list(table.get("Krow"))

plt.plot(sw, krw, 'b-', label='Krw')
plt.plot(sw, krow, 'g-', label='Krow')
plt.xlabel('Sw')
plt.ylabel('Kr')
plt.title('SWOF Corey Relative Permeability')
plt.legend()
plt.grid(True)
plt.show()

Critical vs Connate Water Saturation

The generator distinguishes between connate water saturation ($S_{wc}$) and critical water saturation ($S_{wcr}$):

When swcr is not explicitly set, it defaults to swc. Setting swcr > swc creates a region where water is present but immobile (Krw = 0).