Characterization Package

Documentation for plus fraction and asphaltene characterization in NeqSim.

Table of Contents

Overview

Location: neqsim.thermo.characterization

The characterization package handles petroleum plus fraction and asphaltene characterization:

Plus Fraction Methods

Adding Plus Fractions

import neqsim.thermo.system.SystemSrkEos;

SystemSrkEos fluid = new SystemSrkEos(373.15, 100.0);

// Light components
fluid.addComponent("methane", 0.70);
fluid.addComponent("ethane", 0.10);
fluid.addComponent("propane", 0.08);
fluid.addComponent("n-butane", 0.05);

// C7+ as single pseudo-component
fluid.addTBPfraction("C7+", 0.07, 150.0, 0.78);  // name, moles, MW, SG

Multiple Plus Fractions

// Split C7+ into multiple fractions
fluid.addTBPfraction("C7", 0.02, 96.0, 0.727);
fluid.addTBPfraction("C8", 0.015, 107.0, 0.749);
fluid.addTBPfraction("C9", 0.01, 121.0, 0.768);
fluid.addTBPfraction("C10+", 0.025, 180.0, 0.82);

Characterization Approaches

Pedersen Method

import neqsim.thermo.characterization.PedersenCharacterization;

// Characterize using Pedersen correlations
PedersenCharacterization charPedersen = new PedersenCharacterization(fluid);
charPedersen.characterize();

Whitson Gamma Distribution

import neqsim.thermo.characterization.WhitsonCharacterization;

// Characterize using Whitson gamma distribution
WhitsonCharacterization charWhitson = new WhitsonCharacterization(fluid);
charWhitson.setAlpha(1.0);  // Shape parameter
charWhitson.characterize();

TBP Methods

Adding TBP Fractions

// addTBPfraction(name, moles, MW, specificGravity)
fluid.addTBPfraction("C7", moles, 96.0, 0.727);

// addPlusFraction with characterization
fluid.addPlusFraction("C20+", moles, 400.0, 0.90);

Property Estimation

For pseudo-components, critical properties are estimated using correlations:

Correlation Properties Estimated
Twu Tc, Pc, omega from MW, SG
Lee-Kesler Tc, Pc, omega from Tb, SG
Riazi-Daubert Tb from MW, SG
Pedersen Tc, Pc, omega for petroleum

Lumping Configuration

After plus fraction splitting, lumping reduces the number of pseudo-components for computational efficiency. NeqSim provides a fluent API for clear, explicit configuration.

// PVTlumpingModel: Preserve C6-C9, lump C10+ into 5 groups
fluid.getCharacterization().configureLumping()
    .model("PVTlumpingModel")
    .plusFractionGroups(5)
    .build();

// Standard model: Lump all from C6 into 6 pseudo-components
fluid.getCharacterization().configureLumping()
    .model("standard")
    .totalPseudoComponents(6)
    .build();

// Custom boundaries to match PVT lab report
fluid.getCharacterization().configureLumping()
    .customBoundaries(6, 7, 10, 15, 20)  // C6, C7-C9, C10-C14, C15-C19, C20+
    .build();

// No lumping: keep all SCN components
fluid.getCharacterization().configureLumping()
    .noLumping()
    .build();

Lumping Models Comparison

Model Behavior Use Case
PVTlumpingModel Preserves TBP fractions (C6-C9), lumps only C10+ Standard PVT matching
standard Lumps all heavy fractions from C6 Minimal components for fast simulation
no lumping Keeps all individual SCN components Detailed compositional studies

Quick Reference

I want to… Fluent API
Keep C6-C9 separate, lump C10+ into N groups .model("PVTlumpingModel").plusFractionGroups(N)
Get exactly N total pseudo-components .model("standard").totalPseudoComponents(N)
Match specific PVT lab groupings .customBoundaries(6, 10, 20)
Keep all SCN components .noLumping()

For complete mathematical details, see Fluid Characterization Mathematics.

Asphaltene Characterization

Pedersen’s Asphaltene Method

The PedersenAsphalteneCharacterization class implements Pedersen’s approach for treating asphaltene as a heavy liquid pseudo-component. This enables liquid-liquid equilibrium (LLE) calculations for asphaltene precipitation.

import neqsim.thermo.characterization.PedersenAsphalteneCharacterization;
import neqsim.thermo.system.SystemSrkEos;

// Create fluid system
SystemInterface fluid = new SystemSrkEos(373.15, 50.0);
fluid.addComponent("methane", 0.40);
fluid.addComponent("n-pentane", 0.25);
fluid.addComponent("n-heptane", 0.20);
fluid.addComponent("nC10", 0.10);

// Create and configure asphaltene characterization
PedersenAsphalteneCharacterization asphChar = new PedersenAsphalteneCharacterization();
asphChar.setAsphalteneMW(750.0);     // Molecular weight g/mol
asphChar.setAsphalteneDensity(1.10); // Density g/cm³

// Add asphaltene pseudo-component (BEFORE setting mixing rule)
asphChar.addAsphalteneToSystem(fluid, 0.05);  // 5 mol% asphaltene

// Set mixing rule (AFTER adding all components)
fluid.setMixingRule("classic");

// Print estimated critical properties
System.out.println(asphChar.toString());

Critical Property Correlations

Pedersen’s method estimates critical properties from molecular weight (MW) and liquid density (ρ):

Property Correlation
Critical Temperature (Tc) f(MW, ρ)
Critical Pressure (Pc) f(MW, ρ)
Acentric Factor (ω) f(MW, ρ)
Normal Boiling Point (Tb) f(MW, ρ)

Typical values for asphaltene (MW=750 g/mol, ρ=1.10 g/cm³):

Property Value Unit
Tc 996 K
Pc 16.3 bar
ω 0.925 -
Tb 838 K

TPflash with Automatic Asphaltene Detection

The class provides static methods for TPflash with automatic detection of asphaltene-rich phases:

// Static TPflash - marks asphaltene-rich liquid phases as LIQUID_ASPHALTENE
boolean hasAsphaltene = PedersenAsphalteneCharacterization.TPflash(fluid);

// With explicit T,P specification
boolean hasAsphaltene = PedersenAsphalteneCharacterization.TPflash(fluid, 373.15, 50.0);

// Check result
if (hasAsphaltene) {
    System.out.println("Asphaltene-rich liquid phase detected");
    fluid.prettyPrint();  // Shows "ASPHALTENE LIQUID" column
}

Asphaltene Detection Criteria

A liquid phase is marked as PhaseType.LIQUID_ASPHALTENE when:

Examples

Example 1: Natural Gas with C7+

import neqsim.thermo.system.SystemSrkEos;
import neqsim.thermodynamicoperations.ThermodynamicOperations;

SystemSrkEos gas = new SystemSrkEos(373.15, 100.0);

// Wellstream composition
gas.addComponent("nitrogen", 0.015);
gas.addComponent("CO2", 0.020);
gas.addComponent("methane", 0.750);
gas.addComponent("ethane", 0.080);
gas.addComponent("propane", 0.045);
gas.addComponent("i-butane", 0.012);
gas.addComponent("n-butane", 0.020);
gas.addComponent("i-pentane", 0.008);
gas.addComponent("n-pentane", 0.010);
gas.addComponent("n-hexane", 0.015);

// C7+ fraction
gas.addTBPfraction("C7+", 0.025, 145.0, 0.78);

gas.setMixingRule("classic");

ThermodynamicOperations ops = new ThermodynamicOperations(gas);
ops.TPflash();

System.out.println("Gas fraction: " + gas.getGasPhase().getBeta());
System.out.println("C7+ in gas: " + gas.getGasPhase().getComponent("C7+_PC").getx());

Example 2: Oil Characterization

// Black oil with detailed C7+ split
SystemSrkEos oil = new SystemSrkEos(350.0, 50.0);

oil.addComponent("methane", 0.40);
oil.addComponent("ethane", 0.08);
oil.addComponent("propane", 0.06);
oil.addComponent("n-butane", 0.04);
oil.addComponent("n-pentane", 0.03);
oil.addComponent("n-hexane", 0.03);

// Detailed C7+ split
oil.addTBPfraction("C7", 0.05, 96.0, 0.727);
oil.addTBPfraction("C8", 0.05, 107.0, 0.749);
oil.addTBPfraction("C9", 0.04, 121.0, 0.768);
oil.addTBPfraction("C10", 0.04, 134.0, 0.782);
oil.addTBPfraction("C11", 0.03, 147.0, 0.793);
oil.addTBPfraction("C12+", 0.15, 250.0, 0.85);

oil.setMixingRule("classic");