Heterogeneity

You can set heterogeneous values for the following variables in X1t and X2t models:

• Composition and temperature of the initial fluid,
• Groundwater flow field within the domain,
• Amounts of reactant species, their cutoffs, and target activities and fugacities,
• Kinetic rate law parameters, and
• Single and dual porosity medium properties

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You set a field variable in various ways:

• As a constant value,
• As a random field with a Gaussian distribution,
• As a table file, or in an in-line table,
• Using a node-by-node editor, and
• As the result of evaluating a character string, BASIC script, or compiled C/C++ function

X1t and X2t evaluate field variables at the onset of a run for each node in the domain.

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Transient variables are a special class of field variables that can vary both in space and in time. Options include:

• Internal heat source and heat capacities of the fluid and rock,
• Diffusion coefficient, dispersivities, thermal conductivity, and permeability coefficients,
• Activation energies, pre-exponential factors, rate constants, specific surface areas, nucleation areas, and critical SI's for kinetic reactions,
• Retardation factor, diffusion coefficient, and thermal conductivity of stagnant zones, and
• Mobility of colloids

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Setting up transient field variables is similar to the procedure for specifying heterogeneous field variables or defining custom rate laws. For each transient field variable you need to:

• Supply an equation, BASIC script, script file, or C/C++ function, and
• Enable the “transient” option

React, Phase2, X1t, and X2t evaluate transient field variables at each nodal block upon undertaking each time step over the course of a run.

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