Rock Formation

The formation acts as a thermal reservoir around the production system. It matters whenever a pipe segment references a formation ID, and it strongly influences long-term cooldown, restart, and wall-temperature evolution.

JSON key: initialConfig.formation (EN) · configuracaoInicial.Formacao (PT)

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What This Object Represents

The formation object has two concepts:

• A production-history time scale (productionTime) that sets the thermal memory around the well.
• A list of rock-property sets (properties) identified by id.

Pipe segments consume these IDs using productionPipe[].formationId.

If no formation is referenced in the pipe segment, heat exchange is handled by ambient environment settings or thermal coupling, not by formation properties.

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Production Time

productionTime represents how long the well has already been producing before the simulation starts. Larger values imply a wider pre-heated rock zone and usually slower early cooldown.

JSON key: productionTime (EN) · TempoProducao (PT) Unit: days

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Rock Property Set

Each entry in properties defines one rock type used by one or more pipe segments.

JSON key: properties (EN) · Propriedades (PT)

Each element contains:

• id · id
• conductivity · condutividade [W/(m.degC)]
• specificHeat · calorEspecifico [J/(kg.degC)]
• density · massaEspecifica [kg/m3]

The volumetric thermal storage is $\rho C_p$, and thermal diffusivity is:

$$ \alpha = \frac{k}{\rho C_p} $$

Higher $\alpha$ propagates temperature fronts faster into the formation.

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Practical Modeling Notes

• Use different formation IDs where lithology changes materially along depth/length.
• Avoid unrealistically low conductivity, which can over-insulate the line and overpredict retained heat.
• Buried lines often use formation coupling; exposed subsea lines often rely on seawater environment instead.

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Example: Single Rock Definition

{
  "initialConfig": {
    "formation": {
      "productionTime": 365,
      "properties": [
        {
          "id": 0,
          "conductivity": 2.5,
          "specificHeat": 850.0,
          "density": 2500.0
        }
      ]
    }
  }
}

Example: Two Formation IDs

{
  "initialConfig": {
    "formation": {
      "productionTime": 180,
      "properties": [
        {
          "id": 0,
          "conductivity": 3.0,
          "specificHeat": 900.0,
          "density": 2400.0
        },
        {
          "id": 1,
          "conductivity": 1.5,
          "specificHeat": 950.0,
          "density": 2500.0
        }
      ]
    }
  }
}