This page explains the two comparison paths implemented in NeqSim. It is a screening and software-integration guide, not a regulatory calculation procedure. This model does not establish field accuracy, regulatory compliance, or an uncertainty budget. Verify the applicable handbook revision, facility basis, measurement plan, and reporting requirements with accountable specialists.

Choose the calculation path

Path Current NeqSim behavior Use it for Do not infer
Conventional factors Multiplies annual produced-water volume and pressure drop by the two constants implemented in EmissionsCalculator Reproducing the implemented factor calculation and creating a transparent comparison basis That the constants are current or applicable for a particular report
Thermodynamic screening Runs the ProducedWaterDegassingSystem SRK-CPA convenience model and reports released CO2, methane, and C2+ hydrocarbons by stage Exploring sensitivity to stated flow, temperature, pressure, and assumed gas composition Field calibration, salinity correction, certified uncertainty, or regulatory acceptance

The convenience model assumes 95 mol% water and distributes the remaining 5 mol% using the supplied gas fractions. It uses mixing rule 10 and database interaction parameters. setSalinity stores metadata only; it does not add salt or alter the thermodynamic calculation. See the supported-model guide for the complete basis and limitations.

Conventional factor calculation

The current Java source defines HANDBOOK_F_CH4 = 14.0 and HANDBOOK_F_NMVOC = 3.5, both in g/(m3 water bar). Its static methods return tonnes for the supplied produced-water volume in m3 and pressure drop in bar:

\[U_{\mathrm{CH_4}}=f_{\mathrm{CH_4}}V_{\mathrm{pw}}\Delta P\times10^{-6}\] \[U_{\mathrm{nmVOC}}=f_{\mathrm{nmVOC}}V_{\mathrm{pw}}\Delta P\times10^{-6}\]

calculateConventionalEmissions also returns CO2_tonnes = 0.0 and computes CO2eq_tonnes with the source constants GWP_METHANE = 28.0 and GWP_NMVOC = 2.2. Those are implementation choices, not a promise that the factors or GWP basis match the reporting basis for a new case.

The source-backed static entry points are:

Thermodynamic screening calculation

ProducedWaterDegassingSystem builds three pressure-reduction stages: degasser, compact-flotation-unit (CFU), and caisson. After run(), use getTotalCO2EmissionRate, getTotalMethaneEmissionRate, getTotalNMVOCEmissionRate, and getTotalCO2Equivalents for totals. Use getMethodComparisonReport() or toMap() to carry the comparison into an application logger, report, or data store instead of printing directly to the console.

Executable Java example

The example is intentionally identical to the one in the supported-model guide. ProducedWaterDegassingDocumentationTest#supportedGuideExampleCompilesAndRuns extracts that guide’s Java fence, compiles it with Java 8 settings, loads it, and executes runExample() against the current source. The synthetic lab GWR only demonstrates comparison reporting; it does not calibrate the model.

import java.util.Map;
import neqsim.process.equipment.util.ProducedWaterDegassingSystem;

public class ProducedWaterDegassingExample {
  /**
   * Runs a synthetic screening case with the default database model.
   *
   * @return the executed model for inspection or integration
   */
  public static ProducedWaterDegassingSystem runExample() {
    ProducedWaterDegassingSystem system = new ProducedWaterDegassingSystem("Screening PW");
    system.setWaterFlowRate(100.0, "m3/hr");
    system.setWaterTemperature(80.0, "C");
    system.setInletPressure(30.0, "bara");
    system.setDegasserPressure(4.0, "bara");
    system.setCFUPressure(1.2, "bara");
    system.setCaissonPressure(1.01325, "bara");
    system.setDissolvedGasComposition(
        new String[] {"CO2", "methane", "ethane", "propane"},
        new double[] {0.51, 0.44, 0.04, 0.01});
    system.setTunedInteractionParameters(false);
    system.setLabGWR(0.85);
    system.run();
    Map<String, Object> comparison = system.getValidationResults();
    if (comparison == null || !comparison.containsKey("GWR")) {
      throw new IllegalStateException("Missing lab comparison");
    }
    return system;
  }
}

For a real case, replace the synthetic inputs with traceable facility data and retain the input basis alongside the result. Changing configuration after a model has already been built requires an explicit build() before the next run().

Compare and review

  1. Record the produced-water volume, pressure basis (absolute versus gauge), temperature, assumed or measured gas composition, operating duration, and source revision.
  2. Run the conventional factor calculation with the applicable, independently verified factor basis.
  3. Run the thermodynamic screening case and preserve toMap() output, including processConditions, stage emissions, totals, validation, and the conventional comparison.
  4. Reconcile differences component by component. The conventional implementation does not calculate CO2; the thermodynamic path depends on its fluid and process assumptions.
  5. Validate against representative pressurized-water sampling, evolved-gas volume and composition, and a case-specific uncertainty assessment before operational or reporting use.

The legacy passesRegulatoryCriteria result only applies a fixed 7.5% deviation threshold to the supplied lab GWR. It is not a regulatory decision and is not a complete uncertainty budget.

Evidence and provenance

The 2023 workshop paper Virtual Measurement of Emissions from Produced Water Using an Online Process Simulator describes a separate field-calibrated model. Its reported field results and uncertainties must not be transferred to this convenience builder. In particular, the paper’s saline-water interaction fit is not enabled by setTunedInteractionParameters(false) and is not implemented by setSalinity.

For current implementation evidence, inspect: