Cold CO2 injection in SCCO2 mode

[Prince Otabir]

Dear all,

I am currently trying to extend a working SCO2 + GIRT reactive transport model in PFLOTRAN to investigate the effects of injecting CO₂ at a different temperature than the reservoir (i.e., to simulate a thermal front).

The original isothermal model runs successfully. I then modified the model to include temperature by adding TEMPERATURE DIRICHLET to the flow conditions. I found the following:

• The original isothermal SCO2 + GIRT model runs successfully.
• A model with temperature specified only in the initial and boundary flow conditions also runs successfully.
• The simulation fails only when I specify an injection temperature for the CO₂ source by adding TEMPERATURE DIRICHLET to the injection FLOW_CONDITION.

The injection is currently defined as:

FLOW_CONDITION co2_rate_injection TYPE RATE SCALED_MASS_RATE VOLUME TEMPERATURE DIRICHLET / RATE LIST TIME_UNITS y DATA_UNITS kg/s kg/s kg/s MW 0.d0 0.d0 1.585d-3 0.d0 0.d0 2.d0 0.d0 1.585d-3 0.d0 0.d0 / TEMPERATURE 25.d0 C END

The SCO2 flow solver completes the first timestep successfully, but reactive transport immediately stops with:

ERROR: Unsupported CO2 flow condition in RTResidualNonFlux

My goal is to model the thermal front produced by injecting colder CO2 into a warmer reservoir.

Is this a known limitation of using SOURCE_SINK with SCO2 + GIRT, or is there another recommended approach for specifying the injection temperature? greatly appreciated.

Thank you.

Best regards,

Prince Otabir.

SIMULATION
  SIMULATION_TYPE SUBSURFACE
  PROCESS_MODELS

    SUBSURFACE_FLOW flow
      MODE SCO2
      OPTIONS
        NO_STATE_TRANSITION_OUTPUT
      /
    /

    SUBSURFACE_TRANSPORT transport
      MODE GIRT
    /

  /
END

SUBSURFACE
CO2_DATABASE ./co2_sw.dat

.

.

.

FLOW_CONDITION initial
  TYPE
    LIQUID_PRESSURE HYDROSTATIC
    CO2_MASS_FRACTION DIRICHLET
    SALT_MASS_FRACTION DIRICHLET
    TEMPERATURE DIRICHLET
  /

  DATUM 0.d0 0.d0 100.d0

  GRADIENT
    TEMPERATURE 0.d0 0.d0 -0.0268d0
  /

  LIQUID_PRESSURE 1.2d7
  CO2_MASS_FRACTION 0.d0
  SALT_MASS_FRACTION 1.d-2
  TEMPERATURE 60.d0 C
END

FLOW_CONDITION co2_rate_injection
  SYNC_TIMESTEP_WITH_UPDATE
  TYPE
    RATE SCALED_MASS_RATE VOLUME
    TEMPERATURE DIRICHLET
  /

  RATE LIST
    TIME_UNITS y
    DATA_UNITS kg/s kg/s kg/s MW
    0.d0        0.d0  1.585d-3  0.d0  0.d0
    2.d0        0.d0  1.585d-3  0.d0  0.d0
  /
    TEMPERATURE 60.d0 C
END

[Hammond, Glenn E]

Prince,

Could you please share your complete input deck? I tried to reproduce the issue by using SCALED_MASS_RATE in a regression test, but my simulation ran without any errors.

Glenn

From: pflotra...@googlegroups.com <pflotra...@googlegroups.com> on behalf of Prince Otabir <pot...@gmail.com>
Date: Monday, June 29, 2026 at 8:11 AM
To: pflotran-users <pflotra...@googlegroups.com>
Subject: [pflotran-users: 8817] Cold CO2 injection in SCCO2 mode

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[Prince Otabir]

Thank you for your response.

Kindly find attached the .in file.

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