Mechanical Properties Card Options (CO2E)

Compressibility Options

Geologic media in STOMP-W is considered to be slightly compressible. Compressibility is considered to be an intrinsic property of a rock/soil type. Compressibility can be specified via three options:

Bulk Compressibility

Bulk compressibility is the change in the bulk rock volume with respect to change in pressure at constant temperature:

Bulk and pore compressibility can be related as:

Pore Compressibility

Pore compressibility is the change in pore volume with respect to change in pressure at constant temperature:

Bulk and pore compressibility can be related as:

Specific Storage

Specific storage is the amount of water that a portion of an aquifer releases from storage, per unit mass or volume of aquifer, per unit change in hydraulic head, while remaining fully saturated. Specific storage can be expressed in terms of water density, porosity, water compressibility, and bulk rock compressibility as:

and

Specific storage is converted to bulk compressibility via the specified diffusive porosity and a standard compressibility of water. As with particle density, default values of specific storativity will be computed for null entries of both the specific storativity and its associated units. Default specific storativity is computed from the diffusive porosity and a default value of 1.x10^–7 1/Pa for the compressibility.

Sub-Options

Either or both of the following options can be used with any of the Compressibility Options.

IJK Indexing

If the IJK Indexing option is specified in the Rock/Soil Zonation Card, then or hydraulic conductivity can be specified in an external file with the values for every grid-cell ordered according to the IJK indexing scheme. Units shown in the input line will be applied to all parameters in the external file.

JKI Indexing

If the JKI Indexing option is specified in the Rock/Soil Zonation Card, then or hydraulic conductivity can be specified in an external file with the values for every grid-cell ordered according to the JKI indexing scheme. Units shown in the input line will be applied to all parameters in the external file.

KIJ Indexing

If the KIJ Indexing option is specified in the Rock/Soil Zonation Card, then or hydraulic conductivity can be specified in an external file with the values for every grid-cell ordered according to the KIJ indexing scheme. Units shown in the input line will be applied to all parameters in the external file.

Dual Porosity/Permeability Model for Fractured Systems

If the key words 'dp,' 'dual porosity,' or 'fractured' appear in the rock/soil name specified inthe Rock/Soil Zonation Card, this indicates a dual porosity medium and the reading of both matrix and fracture properties (e.g., Fracture and Matrix Intrinsic Porosity) is triggered.

Tortuosity Functions

Tortuosity functions are required for simulations that involve solute transport or diffusion of components through phases (e.g., water vapor diffusing through the gas phase or dissolved oil diffusing through the aqueous phase). Tortuosities can be computed either as:

Constants

When choosing the constant option, specific input values for the tortuosity factor may be specified.

Millington and Quirk Model

Tortuosity can be specified using functions of the phase saturation and diffusive porosity according to the formulation of Millington and Quirk (1959):

Symbols
τ_l	tortuosity
n_D	diffusive porosity
s_l	aqueous saturation

Millington and Quirk Gas with Constant Aqueous

In this option the gas phase tortuosity is based on the formulation of Millington and Quirk (1959) and the aqueous tortuosity is specified by a constant tortuosity factor.

Marshall

Tortuosity can be specified using functions of the phase saturation and diffusive porosity according to the formulation of Marshall (1959):

Symbols
τ_l	tortuosity
n_D	diffusive porosity
s_l	aqueous saturation

References
Marshall, T. J. (1959), The diffusion of gases through porous media. J. Soil Sci., 10, 79–82, doi:10.1111/j.1365-2389.1959.tb00667.x.

Millington, R. J. and J. P. Quirk. 1959. Permeability of porous media. Nature 183:387-388.