The Boundary Conditions Card for STOMP-CO2e can be used to specify boundary conditions for the energy, fluid flow, or salt. Boundary conditions are one of two types: 1) Dirichlet or 2) Neumann. Dirichlet-type boundary conditions specify state conditions at the boundary surface centroid (i.e., temperature, pressure, phase saturation). Neumann-type boundary conditions specify either fluxes (i.e., heat flux, fluid flux, salt flux) across a boundary surface. For STOMP-CO2E the specification order is always: 1) energy, 2) aqueous, 3) gas, 4) dissolved salt, and 5) reactive species.

Energy Boundary Condition Options

Dirichlet-type boundary where the temperature is specified at the boundary surface centroid. The Dirichlet boundary condition is equivalent to specifying the value for the primary unknown on the boundary surface. Assigned values of primary variables are used to compute secondary variables for the boundary surface. Average properties for heat transport between a boundary surface and the adjacent node are computed using user specified averaging schemes between the values of the properties on the boundary surface and adjacent node.

Dirichlet-type boundary where the temperature is set to be equal with the temperature at the grid-cell centroid at the start of the simulation.

Neumann-type boundary where the heat flux is specified across the boundary surface. Positive flux is in the direction of the surface normal.

Energy migrates across the boundary surface only via aqueous and gas phase advection in the direction of the boundary-surface normal (i.e., out of the domain). As diffusive heat transport across the boundary surface is not considered the temperature entry is ignored.

A geothermal gradient is applied to the boundary condition domain given a base temperature.

Neumann-type boundary where the heat flux is zero.

Aqueous Phase Boundary Condition Options

Aqueous Flow Boundary Condition Options are available only if the Energy Boundary Condition Option is **not** of type Neumann.

Dirichlet-type boundary where the aqueous pressure is specified at the boundary surface centroid. The Dirichlet boundary condition is equivalent to specifying the value for the primary unknown on the boundary surface. Assigned values of primary variables are used to compute secondary variables for the boundary surface. Average properties for fluid transport between a boundary surface and the adjacent node are computed using user specified averaging schemes between the values of the properties on the boundary surface and adjacent node.

Dirichlet-type boundary where the aqueous pressure is set to be in hydrostatic equilibrium with the aqueous pressure at the grid-cell centroid at the start of the simulation.

Neumann-type boundary where the aqueous volumetric flux is specified across the boundary surface. Positive flux is in the direction of the surface normal.

A hydraulic gradient is applied to the boundary condition domain given a base aqueous pressure.

The unit gradient establishes a fluid pressure on the boundary surface equal to the fluid pressure at the adjacent node modified by the hydraulic gradient for the fluid.

West Boundary Example

A unit gradient in the phase hydraulic head is equivalent to setting the normalized Darcy velocity equal to minus one, according to

for a “west” boundary (WB) surface. Phase pressure on the boundary surface is computed by solving

for the boundary pressure for a “west” boundary (WB) surface. Unit gradient boundary pressures are computed with each Newton-Raphson iteration.

The saturated boundary condition is recognized for liquid-gas systems and performs as a dynamic Dirichlet boundary condition, where zero capillary pressure is maintained on the boundary surface. The saturated boundary condition fixes the aqueous pressure equal to the gas pressure on a boundary surface regardless of the boundary condition for the gas pressure. For a single-phase system, the gas pressure is fixed through the initial conditions and the aqueous pressure is maintained on a saturated boundary equal to this gas pressure. For a two-phase system, the gas pressure on a boundary surface is user specified according to the gas-phase boundary conditions. The saturated boundary condition for the aqueous phase fixes the aqueous pressure at the boundary surface equal to the gas pressure. Saturated boundary pressures are computed with each Newton-Raphson iteration.

Neumann-type boundary where the aqueous volumetric flux is zero.

Gas Phase Boundary Condition Options

Gas Flow Boundary Condition Options are available only if the Energy Boundary Condition Option is **not** of type Neumann.

Dirichlet-type boundary where the gas pressure is specified at the boundary surface centroid. The Dirichlet boundary condition is equivalent to specifying the value for the primary unknown on the boundary surface. Assigned values of primary variables are used to compute secondary variables for the boundary surface. Average properties for fluid transport between a boundary surface and the adjacent node are computed using user specified averaging schemes between the values of the properties on the boundary surface and adjacent node.

Dirichlet-type boundary where the gas pressure is set to be in hydrostatic equilibrium with the gas pressure at the grid-cell centroid at the start of the simulation.

Neumann-type boundary where the gas volumetric flux is specified across the boundary surface. Positive flux is in the direction of the surface normal.

A hydraulic gradient is applied to the boundary condition domain given a base gas pressure.

Neumann-type boundary where the gas volumetric flux is zero.

Salt Boundary Condition Options

Salt Boundary Condition Options are available only if the Flow Boundary Condition Option is **not** zero flux.

Dirichlet-type boundary where the aqueous relative saturation of salt (in terms of salt saturation to salt solubility) is specified at the boundary surface centroid. Salt migrates across the boundary surface via diffusion or advection of the aqueous phase.

Dirichlet-type boundary where the aqueous relative saturation of salt (in terms of salt saturation to salt solubility) is specified at the boundary surface centroid. Salt is allowed to migrate across the boundary surface only in the direction opposite of the boundary-surface normal (i.e., into the domain).

Dirichlet-type boundary where the salt mass fraction in aqueous liquid is specified.

Dirichlet-type boundary where the salt mass fraction in aqueous liquid is specified at the boundary surface centroid.. Salt is allowed to migrate across the boundary surface only in the direction opposite of the boundary-surface normal (i.e., into the domain).

Salt is allowed to migrate across the boundary surface only in the direction of the boundary-surface normal (i.e., out of the domain).

Dirichlet-type boundary where the molality of salt in aqueous liquid is specified.

Dirichlet-type boundary where the molality of salt in aqueous liquid is specified at the boundary surface centroid.. Salt is allowed to migrate across the boundary surface only in the direction opposite of the boundary-surface normal (i.e., into the domain).

Dirichlet-type boundary where the aqueous concentration of of salt is specified.

Dirichlet-type boundary where the aqueous concentration of salt is specified at the boundary surface centroid.. Salt is allowed to migrate across the boundary surface only in the direction opposite of the boundary-surface normal (i.e., into the domain).

Dirichlet-type boundary where the aqueous saturation is set to be equal to the aqueous saturation at the grid-cell centroid at the start of the simulation. Salt migrate across the boundary surface via diffusion or advection of the aqueous phases.

Neumann-type boundary where the salt flux is zero.

Species Boundary Condition Options

Dirichlet-type boundary where the aqueous concentration, in terms of species per mass of aqueous phase, of the species is specified at the boundary surface centroid. Species migrate across the boundary surface via diffusion through the aqueous phase or advection with the aqueous phase.

Dirichlet-type boundary where the aqueous concentration, in terms of species per mass of aqueous phase, of the species is specified at the boundary surface centroid. Species migrate across the boundary surface only via aqueous phase advection in the direction opposite of the boundary-surface normal (i.e., into the domain).

Dirichlet-type boundary where the aqueous concentration, in terms of species per mass of aqueous phase, of the species is specified at the boundary surface centroid. Species migrate across the boundary surface only via aqueous phase advection. When aqueous phase flux is in the direction of the boundary-surface normal (i.e., out of the domain), the species concentration is that at the grid-cell centroid, and when aqueous phase flux is in the direction opposite of the boundary-surface normal (i.e., into the domain), the species concentration is that specified via the input.

Dirichlet-type boundary where the aqueous concentration is set to be equal to the aqueous concentration at the grid-cell centroid at the start of the simulation. Species migrate across the boundary surface via diffusion through the aqueous phase or advection with the aqueous phase.

Species migrate across the boundary surface only via aqueous phase advection in the direction of the boundary-surface normal (i.e., out of the domain). As diffusive transport across the boundary surface is not considered the species concentration entry is ignored.

Dirichlet-type boundary where the gas phase of the species is specified at the boundary surface centroid. Species migrate across the boundary surface only via aqueous phase advection. When aqueous phase flux is in the direction of the boundary-surface normal (i.e., out of the domain), the species concentration is at the grid-cell centroid, and when aqueous phase flux is in the direction opposite of the boundary-surface normal (i.e., into the domain), the species concentration is specified via the input.

Dirichlet-type boundary where the species migrate across the boundary surface via aqueous and gas phase advection.

Dirichlet-type boundary where the species migrate across the boundary surface only via gas phase advection in the direction opposite the boundary-surface normal (i.e., into the domain).

Dirichlet-type boundary where the species migrate across the boundary surface only via fluid (aqueous and gaseous) phase advection in the direction opposite the boundary-surface normal (i.e., into the domain).

Dirichlet-type boundary where the volumetric concentration, in terms of species per volume of fluid phase (aqueous and gaseous), of the species is specified at the boundary surface centroid. Species migrate across the boundary surface via diffusion through the fluid phase or advection with the fluid phase.

Dirichlet-type boundary where the gas concentration, in terms of species per mass of gas phase, of the species is specified at the boundary surface centroid. Species migrate across the boundary surface via diffusion through the gas phase or advection with the gas phase.

Neumann-type boundary where the species flux is zero. Species are prevented from crossing the boundary surface regardless of their aqueous-phase concentration.

- Simulation Title Card
- Solution Control Card
- Grid Card
- Internal Boundary Surfaces
- Inactive Nodes Card
- Rock/Soil Zonation Card
- Mechanical Properties Card
- Hydraulic Properties Card
- Saturation Function Card
- Aqueous Phase Relative Permeability Card
- Gas Phase Relative Permeability Card
- Thermal Properties Card
- Salt Transport Card
- Initial Conditions Card
- Boundary ConditionsCard
- Coupled Well Card
- Source Card
- Output Control Card
- Surface Flux Card

Last Update: August 2019 | Pacific Northwest National Laboratory