Surfaces, wells, and materials¶

Surface roles¶

Surface order and role determine how the PLC and exported marker IDs are constructed.

Role	Purpose	Marker for surface index `i`
`border`	External domain boundary	`i + 1`
`unit`	Internal stratigraphic interface	`i + 1`
`fault`	Internal fault constraint	`1000 + i`

An index is zero-based and follows the order of MeshCase.surfaces. Keep this order stable if downstream boundary-condition files use numeric markers.

surfaces = [
    SurfaceSpec("bottom", bottom, role="border"),  # marker 1
    SurfaceSpec("top", top, role="border"),        # marker 2
    SurfaceSpec("fault", fault, role="fault"),     # marker 1002
]

Material seeds¶

A formation material requires at least one seed strictly inside every volume region that should receive its attribute value:

materials = [
    MaterialSpec("lower", [0.0, 0.0, -500.0], attribute=1),
    MaterialSpec("upper", [0.0, 0.0, 500.0], attribute=2),
]

The attribute becomes the MaterialID cell value and the Exodus element-block ID. A material with type="FAULT" is surface-only metadata and does not create a volumetric TetGen region.

If no materials are supplied, the TetGen wrapper creates a default material region near the PLC centre with attribute zero. Explicit seeds are strongly recommended for layered models.

Wells¶

Well coordinates are ordered polylines. Intersections with surfaces are inserted into the refined trajectory before volume meshing.

well = WellSpec(
    "injection_well",
    well_points,
    target_size=10.0,
    marker=2001,
)

Set marker explicitly when Exodus node-set or block IDs must remain stable. Automatic well markers depend on the number and order of datasets.

Watertight volume requirements¶

TetGen needs a closed, consistent piecewise-linear complex. Before generating a volume mesh, check that:

border surfaces enclose the complete domain;
intersections meet without gaps larger than intersection_tolerance;
internal surfaces do not extend inconsistently outside the domain;
material seeds lie inside closed regions; and
conforming surface meshes have no missing pieces.