CO2 Injection Well Analysis Module

Five new classes provide an integrated analysis workflow for CO2 injection wells where impurity enrichment (hydrogen, nitrogen, methane) in the gas phase during two-phase conditions is a safety concern.

Class Overview

Class Package Purpose
CO2InjectionWellAnalyzer process.equipment.pipeline High-level orchestrator — runs all analyses and returns safety verdict
ImpurityMonitor process.measurementdevice Phase-partitioned composition tracking with alarm thresholds
TransientWellbore process.equipment.pipeline Shutdown cooling simulation (exponential decay to geothermal profile)
CO2FlowCorrections process.equipment.pipeline Static utility — CO2-specific holdup and friction correction factors
PipeBeggsAndBrills process.equipment.pipeline Enhanced with formation temperature gradient support (NIP-1)

Architecture

CO2InjectionWellAnalyzer (orchestrator)
├── PipeBeggsAndBrills (steady-state wellbore flow)
│   ├── Formation Temperature Gradient (NIP-1)
│   └── CO2FlowCorrections (NIP-4)
├── ImpurityMonitor (NIP-2)
│   └── Phase-partitioned K-value tracking
├── TransientWellbore (NIP-3)
│   └── Shutdown cooling + phase evolution
└── ThrottlingValve (choke JT analysis)

CO2InjectionWellAnalyzer

Package: neqsim.process.equipment.pipeline

Combines steady-state wellbore simulation, phase boundary scanning, impurity enrichment mapping, shutdown assessment, and choke JT analysis into a single analysis tool.

API

CO2InjectionWellAnalyzer analyzer = new CO2InjectionWellAnalyzer("InjectionWell-1");

// Configure
analyzer.setFluid(co2Fluid);
analyzer.setWellGeometry(1300.0, 0.1571, 4.5e-5);        // depth, ID, roughness [m]
analyzer.setOperatingConditions(90.0, 25.0, 150000.0);    // WHP [bara], WHT [C], flow [kg/hr]
analyzer.setFormationTemperature(4.0, 43.0);               // top C, bottom C
analyzer.addTrackedComponent("hydrogen", 0.04);            // name, alarm mol frac

// Run
analyzer.runFullAnalysis();

// Results
boolean safe = analyzer.isSafeToOperate();
Map<String, Object> results = analyzer.getResults();

Results Map Keys

Key Type Description
safe_to_operate Boolean Overall safety verdict
design_BHP_bara Double Bottom-hole pressure at design rate
design_BHT_C Double Bottom-hole temperature at design rate
min_safe_WHP_bara Double Minimum wellhead pressure for single-phase
two_phase_conditions List P-T points where two phases form
max_impurity_concentrations Map Peak gas-phase concentrations per component
shutdown_safe Boolean Whether shutdown at design WHP is safe

ImpurityMonitor

Package: neqsim.process.measurementdevice

A measurement device that reads from a connected stream and tracks the phase-partitioned composition of selected impurity components. Reports enrichment factors (K-values) and triggers alarms when gas-phase concentrations exceed configurable thresholds.

API

ImpurityMonitor monitor = new ImpurityMonitor("WH-H2-Monitor", stream);
monitor.addTrackedComponent("hydrogen", 0.04);   // alarm at 4 mol%
monitor.addTrackedComponent("nitrogen", 0.10);   // alarm at 10 mol%
monitor.setPrimaryComponent("hydrogen");          // for getMeasuredValue()

// After process.run():
double h2InGas   = monitor.getGasPhaseMoleFraction("hydrogen");    // y_H2
double h2InLiq   = monitor.getLiquidPhaseMoleFraction("hydrogen");  // x_H2
double h2Bulk    = monitor.getBulkMoleFraction("hydrogen");         // z_H2
double enrichment = monitor.getEnrichmentFactor("hydrogen");       // y/z
boolean alarm     = monitor.isAlarmExceeded("hydrogen");           // y > 0.04?
int nPhases       = monitor.getNumberOfPhases();
double gasFrac    = monitor.getGasPhaseFraction();                 // gas beta

Map<String, Map<String, Double>> report = monitor.getFullReport();

Supported Units for getMeasuredValue(String unit)

Unit Description
"mol%" Mole percent (default)
"ppm" Parts per million
"mole fraction" Raw mole fraction

TransientWellbore

Package: neqsim.process.equipment.pipeline

Simulates the thermal evolution of a wellbore after injection stops. The model divides the wellbore into vertical segments and applies exponential temperature decay toward the formation temperature at each depth. At each time step, a TP flash determines if two-phase conditions develop and tracks impurity enrichment.

API

TransientWellbore well = new TransientWellbore("InjWell", feedStream);
well.setWellDepth(1300.0);                              // meters
well.setTubingDiameter(0.1571);                         // meters
well.setFormationTemperature(277.15, 316.15);           // top K, bottom K
well.setShutdownCoolingRate(5.0);                       // time constant [hours]
well.setNumberOfSegments(20);
well.setRadialHeatTransferCoefficient(25.0);            // W/(m2 K)
well.setDepressurizationRate(5.0);                      // bar/hr (0 = constant P)

// Run
well.runShutdownSimulation(24.0, 1.0);  // 24 hours, 1-hour steps

// Results
List<TransientSnapshot> snapshots = well.getSnapshots();
List<double[]> tempProfiles = well.getTemperatureProfiles();
double[] times = well.getTimePoints();
double maxH2 = well.getMaxGasPhaseConcentration("hydrogen");

TransientSnapshot Fields

Field Type Description
timeHours double Simulation time
depths[] double[] Depth at each segment [m]
temperatures[] double[] Temperature at each segment [K]
pressures[] double[] Pressure at each segment [bara]
numberOfPhases[] int[] Phase count at each segment
gasFraction[] double[] Gas mole fraction at each segment
gasCompositions Map Component gas-phase compositions at each segment

CO2FlowCorrections

Package: neqsim.process.equipment.pipeline

Static utility class providing CO2-specific correction factors for the Beggs and Brill (1973) multiphase flow correlation. The standard correlation was developed for oil-gas-water systems and may not accurately represent CO2-dominated streams where the liquid phase is dense-phase CO2.

API

// Check applicability
boolean isCO2 = CO2FlowCorrections.isCO2DominatedFluid(system);   // >50 mol% CO2
double xCO2   = CO2FlowCorrections.getCO2MoleFraction(system);

// Correction factors
double holdupFactor  = CO2FlowCorrections.getLiquidHoldupCorrectionFactor(system);   // 0.70-0.85
double frictionFactor = CO2FlowCorrections.getFrictionCorrectionFactor(system);      // 0.85-0.95

// Phase state
boolean dense = CO2FlowCorrections.isDensePhase(system);           // T>Tc AND P>Pc
double Tr     = CO2FlowCorrections.getReducedTemperature(system);  // T/Tc
double Pr     = CO2FlowCorrections.getReducedPressure(system);     // P/Pc

// Surface tension
double sigma  = CO2FlowCorrections.estimateCO2SurfaceTension(system);  // N/m

Correction Factor Behaviour

Condition Holdup Factor Friction Factor
Near-critical ($T_r > 0.95$) 0.70 0.85
Intermediate ($0.85 < T_r < 0.95$) 0.70 - 0.85 (linear) 0.95
Subcritical ($T_r < 0.85$) 0.85 0.95

Constants: $T_c = 304.13$ K, $P_c = 73.77$ bara, CO2 threshold = 50 mol%.

Reference: Peletiri, S.P., Rahmanian, N. and Mujtaba, I.M. (2018). CO2 Pipeline Design: A Review. Energies, 11(9), 2184.

PipeBeggsAndBrills — Formation Temperature Gradient (NIP-1)

Package: neqsim.process.equipment.pipeline

The existing PipeBeggsAndBrills class was enhanced with a formation temperature gradient model. Previously, only a constant surface temperature could be specified. Now the heat transfer calculation uses a depth-dependent formation temperature profile for realistic geothermal gradient modelling.

New Methods

PipeBeggsAndBrills pipe = new PipeBeggsAndBrills(inletStream);

// Set formation temperature gradient
// For a well with 4 C at wellhead and 30 C/km geothermal gradient:
pipe.setFormationTemperatureGradient(4.0, -0.03, "C");
//                                  ^inlet ^gradient ^unit
// Sign convention: negative gradient = temperature INCREASES with depth
//                  (negative elevation change in injection wells)

double grad = pipe.getFormationTemperatureGradient();   // returns K/m

Impact on Results (Example)

Parameter Without Gradient With Gradient Difference
BHT 4.1 °C 42.8 °C +38.7 °C
BHP 200.5 bara 183.7 bara -16.8 bar

The formation temperature gradient significantly affects the fluid density along the wellbore, which changes the hydrostatic pressure contribution. Warmer fluid is less dense, resulting in lower bottom-hole pressure.

Integration Workflow

These classes are designed to work together for CO2 injection well safety analysis. The typical workflow is:

  1. Create fluid — Define CO2-rich injection composition
  2. Steady-state — Run PipeBeggsAndBrills with formation gradient
  3. Phase scan — Map the two-phase region with TP flash
  4. Enrichment — Use ImpurityMonitor to track H2/N2 in gas phase
  5. Shutdown — Run TransientWellbore for thermal transient
  6. Safety — Use CO2InjectionWellAnalyzer for integrated assessment

Python / Jupyter Example

from neqsim import jneqsim
import jpype

# Load classes
SystemSrkEos = jneqsim.thermo.system.SystemSrkEos
Stream = jneqsim.process.equipment.stream.Stream
CO2InjectionWellAnalyzer = jpype.JClass(
    "neqsim.process.equipment.pipeline.CO2InjectionWellAnalyzer")

# Create fluid
fluid = SystemSrkEos(273.15 + 25.0, 90.0)
fluid.addComponent("CO2", 0.96225)
fluid.addComponent("nitrogen", 0.01975)
fluid.addComponent("methane", 0.008)
fluid.addComponent("hydrogen", 0.0075)
fluid.addComponent("argon", 0.00175)
fluid.addComponent("CO", 0.00075)
fluid.setMixingRule("classic")

# Run integrated analysis
analyzer = CO2InjectionWellAnalyzer("InjectionWell-1")
analyzer.setFluid(fluid)
analyzer.setWellGeometry(1300.0, 0.1571, 4.5e-5)
analyzer.setOperatingConditions(90.0, 25.0, 150000.0)
analyzer.setFormationTemperature(4.0, 43.0)
analyzer.addTrackedComponent("hydrogen", 0.04)
analyzer.runFullAnalysis()

print("Safe:", analyzer.isSafeToOperate())
results = dict(analyzer.getResults())
print("Min safe WHP:", results.get("min_safe_WHP_bara"), "bara")