Boundary Conditions¶

Boundary conditions close the 1D conservation equations by specifying what is imposed at the inlet, outlet, or service-line boundary. In Marlim3, some boundaries are configured inside initialConfig, while others are top-level objects.

Closure Strategy¶

The solver needs a closure strategy for the production system:

Inlet-boundary driven: use pressureCondition or flowRatePressureCondition inside initialConfig.
Source-driven: omit inlet boundary objects and inject fluid through source accessories (ipr, liquidSource, massSource, gasSource, etc.).

For the gas injection system:

Service-line: if gas line exists, use gasInj for service-line inlet conditions.

If no inlet boundary object is provided, the line is treated as closed at the endpoint and inflow must come from sources inside the system.

Inlet: Pressure Condition¶

Use this when inlet pressure is known and the solver should determine the resulting flow rate from the overall pressure balance.

What is imposed over time:

Pressure [kgf/cm²]
Temperature [°C]
Fluid quality (free-gas mass divided by total associated mass)
Complementary-fluid volumetric ratio

JSON key: initialConfig.pressureCondition (EN) · configuracaoInicial.condicaoPressao (PT)

Sub-keys:

active · ativo

time · tempo

pressure · pressao

temperature · temperatura

fluidQuality · titulo

betaRatio · razaoBeta

Inlet: Flow-Rate + Pressure Condition¶

This boundary fully defines the system from the inlet side by imposing inlet pressure and inlet mass flow simultaneously. It is intended for steady-state only; in transient mode, outlet information is still needed because wave propagation matters.

What is imposed over time:

Pressure [kgf/cm²]
Temperature [°C]
Mass flow rate [kg/s]
Complementary-fluid ratio

JSON key: initialConfig.flowRatePressureCondition (EN) · configuracaoInicial.condicaoVazPres (PT)

Sub-keys:

active · ativo

time · tempo

pressure · pressao

temperature · temperatura

massFlowRate · VazMass

betaRatio · razaoBeta

Inlet by Sources (No Inlet Boundary Object)¶

Instead of imposing conditions at the first endpoint, fluid can enter through sources positioned along the production line. This is useful for wells where inflow enters at a reservoir-coupled location rather than at pipe coordinate zero.

Typical source-based inlet choices:

ipr for reservoir inflow
liquidSource for standard-condition liquid rate
massSource for total mass inflow
gasSource for gas inflow

See accessories.md for source configuration.

Outlet: Separator Pressure¶

The standard outlet boundary is a downstream pressure schedule representing separator or receiving-manifold pressure.

JSON key: separator (EN) · separador (PT)

Sub-keys: active · ativo, time · tempo, pressure · pressao

Outlet: Surface Choke¶

The surface choke is a fixed-position outlet restriction, before the separator.

JSON key: surfaceChoke (EN) · chokeSup (PT)

Main fields:

cvCurve (0 = area ratio, 1 = stem displacement)
time / tempo
opening / abertura
dischargeCoefficient / coeficienteDescarga
model / modelo (currently only 0 = Sachdeva)
x1, cv1 for stem-displacement mode

Reverse-Flow Prevention at Outlet¶

The production-system outlet can be protected by a check valve configured in initialConfig.

JSON key: initialConfig.checkValve (EN) · configuracaoInicial.CheckValve (PT) Values: 0 = reverse gas inflow allowed, 1 = reverse flow blocked at last boundary

Service-Line Gas Injection Boundary¶

When the service line exists, gasInj defines its inlet boundary condition.

JSON key: gasInj (EN/PT)

Main fields:

bcType / tipoCC
0 = injection pressure
1 = injection flow rate
time / tempo
temperature / temperatura
gasFlowRate / vazaoGas
injectionPressures / pressaoInjecao
initialFlowRateGuess / chuteVazaoInjecao

Injection-Well Boundary Condition¶

Injection-well simulations use a dedicated top-level boundary object with six boundary-condition modes.

JSON key: injectionWellBC (EN) · CondicaoContPocInjec (PT)

Core fields:

fluidType / tipoFluido
0 = user-provided liquid from complementary fluid
1 = water (requires salinity)
2 = CO2-rich gas via flash table (.tab)
3 = CO2-rich gas via compositional model (.ctm)
pvtsimFile / arquivoPvtsim
boundaryCondition / condContorno
injectionTemp / tempInj
stdLiquidFlowRate / vazLiq
injectionPressure / presInjec
bottomholePressure / presFundo

Boundary-condition modes¶

Mode	Required quantities
0	`stdLiquidFlowRate` + IPR
1	`injectionPressure` + IPR
2	`bottomholePressure` + IPR
3	`injectionPressure` + `bottomholePressure`
4	`stdLiquidFlowRate` + `injectionPressure`
5	`stdLiquidFlowRate` + `bottomholePressure`

All six modes require injectionTemp.

Injection-side choke¶

JSON key: injectionChoke (EN) · chokeInj (PT)

This is a single-phase gas choke with:

active / ativo
time / tempo
opening / abertura
dischargeCoefficient / coeficienteDescarga

Tips for choosing a Boundary Strategy¶

Use pressureCondition when upstream pressure is the natural control variable.
Use flowRatePressureCondition only for steady-state one-sided closure studies.
Use ipr when inflow depends on reservoir drawdown.

Example: Pressure Inlet + Separator¶

{
  "separator": {
    "active": true,
    "time": [0, 3600],
    "pressure": [50.0, 45.0]
  },
  "initialConfig": {
    "pressureCondition": {
      "active": true,
      "time": [0],
      "pressure": [200.0],
      "temperature": [80.0],
      "fluidQuality": [0.0],
      "betaRatio": [0.0]
    }
  }
}

Example: Service-Line Injection BC¶

{
  "initialConfig": {
    "gasLine": true
  },
  "gasInj": {
    "active": true,
    "bcType": 0,
    "time": [0, 3600],
    "temperature": [25.0, 25.0],
    "injectionPressures": [120.0, 115.0]
  }
}

Tip

Start with one clear closure strategy, validate steady-state first, then introduce time-varying ramps, chokes, and coupling effects.