The neqsim.pvtsimulation package contains compositional simulations for reservoir-fluid characterization, laboratory-test reconstruction, and PVT quality control. Build and characterize the thermodynamic system first, then give each experiment its own clone so that one pressure path does not affect another.

Choose a simulation

Engineering task Main class Typical results
Bubble-point or dew-point pressure SaturationPressure Saturation pressure
Constant-composition expansion (CCE) ConstantMassExpansion Relative volume, Y-factor, density, and compressibility
Constant-volume depletion (CVD) ConstantVolumeDepletion Liquid dropout, depletion, Z-factor, and material-balance checks
Differential liberation (DL) DifferentialLiberation Oil FVF, solution GOR, gas FVF, and oil density
Surface-separation study SeparatorTest, MultiStageSeparatorTest Stage and total GOR, oil FVF, stock-tank density, and API gravity
Injection-gas swelling SwellingTest Saturation pressure and relative oil volume versus injected gas
Minimum miscibility pressure MMPCalculator MMP, recovery curve, and interpreted miscibility mechanism
Viscosity pressure sweep ViscositySim Gas, oil, and aqueous viscosities

The CCE, CVD, DL, single-stage separator, swelling, and viscosity classes use runCalc(). SaturationPressure, MultiStageSeparatorTest, and MMPCalculator use run().

Runnable multi-stage separator example

This complete example uses kelvin and bara in the thermodynamic-system constructor. setReservoirConditions and addSeparatorStage use degrees Celsius and bara.

import java.util.List;
import neqsim.pvtsimulation.simulation.MultiStageSeparatorTest;
import neqsim.pvtsimulation.simulation.MultiStageSeparatorTest.SeparatorStageResult;
import neqsim.thermo.system.SystemInterface;
import neqsim.thermo.system.SystemSrkEos;

public final class PvtSeparatorQuickStart {
  private PvtSeparatorQuickStart() {}

  public static void main(String[] args) {
    SystemInterface reservoirFluid = new SystemSrkEos(373.15, 300.0);
    reservoirFluid.addComponent("nitrogen", 0.5);
    reservoirFluid.addComponent("CO2", 2.0);
    reservoirFluid.addComponent("methane", 45.0);
    reservoirFluid.addComponent("ethane", 8.0);
    reservoirFluid.addComponent("propane", 5.0);
    reservoirFluid.addComponent("i-butane", 1.5);
    reservoirFluid.addComponent("n-butane", 2.5);
    reservoirFluid.addComponent("i-pentane", 1.0);
    reservoirFluid.addComponent("n-pentane", 1.5);
    reservoirFluid.addComponent("n-hexane", 3.0);
    reservoirFluid.addComponent("n-heptane", 30.0);
    reservoirFluid.setMixingRule("classic");
    reservoirFluid.setMultiPhaseCheck(true);

    MultiStageSeparatorTest separatorTest =
        new MultiStageSeparatorTest(reservoirFluid);
    separatorTest.setReservoirConditions(300.0, 100.0);
    separatorTest.addSeparatorStage(50.0, 40.0, "HP separator");
    separatorTest.addSeparatorStage(10.0, 30.0, "LP separator");
    separatorTest.addStockTankStage();
    separatorTest.run();

    List<SeparatorStageResult> stages = separatorTest.getStageResults();
    for (SeparatorStageResult stage : stages) {
      System.out.printf(
          "%s: %.3f bara, %.2f C, cumulative GOR %.3f Sm3/Sm3%n",
          stage.getStageName(), stage.getPressure(), stage.getTemperature(),
          stage.getCumulativeGOR());
    }

    System.out.printf("Total GOR: %.3f Sm3/Sm3%n", separatorTest.getTotalGOR());
    System.out.printf("Oil FVF: %.5f m3/Sm3%n", separatorTest.getBo());
    System.out.printf(
        "Stock-tank density: %.2f kg/m3%n",
        separatorTest.getStockTankOilDensity());
  }
}

The repository test neqsim.pvtsimulation.PvtSimulationDocumentationTest compiles and executes this same workflow. The result magnitudes depend on the fluid characterization and equation of state; do not use the example composition as calibrated field data.

Working with laboratory data

  1. Reproduce the laboratory composition, plus-fraction characterization, equation of state, mixing rule, and volume-shift choices.
  2. Use the measured temperature and pressure schedule without silently changing gauge, absolute, standard, or reservoir units.
  3. Run each experiment from a separate clone of the characterized base fluid.
  4. Compare primary observables and material balance before tuning model parameters.
  5. Record the NeqSim version, input composition, characterization settings, and fitted parameters with the result.

Several simulations expose experimental-data and quality-control methods. Their calibration interfaces are experiment-specific; verify the current Java source and Javadocs before building an automated regression workflow.