The Reservoir Description view

Specify the grid properties for a simulation using the Reservoir Description view.

Reservoir Properties tab

The Reservoir Properties tab contains the reservoir properties table; a list of properties that will be built into the deck. In this table, properties from the static model (the 3D grid associated with the case) can be connected to the simulation properties.

Name Property name. Click in the empty bottom Name field to add other properties.

Mat/Frac This is used to identify the property as a matrix or a fracture property.

Constant Enabled if read option is CON. A single value that represents a property.

Source Property from the static model that is used to fill the values array for the property. Model must be VALUE. Selected from a combo box edit.

Component (GEM™ only) Associate a component with the selected property.

Sector Name Used to define the sector name for the SECTORARRAY property.

A reservoir property is an array of one or more values. The property defines a value for each cell in the simulation grid.

A number of other properties can be defined as input with a reservoir description. To add a property to the table, left-click in the empty row at the bottom of the table, in the "Name" column, and select a property.

There are several ways that properties can be defined. The properties can either come from the upstream workflow or can be simply defined as part of the reservoir description. Properties can be defined in various ways. The following are the most common ways that properties are defined:

CON A single value is used for all cells in the reservoir. This is convenient when a property is not well understood. It is also useful to switch between CON and VALUE to see the effect of a property on the simulation.

IVAR A single value is used for all cells in the reservoir. This is convenient when a property is not well understood. It is also useful to switch between CON and VALUE to see the effect of a property on the simulation.

JVAR Used to indicate values that vary in the J direction, but which are constant in the other two directions.

KVAR Used to indicate values that vary in the K direction, but which are constant in the other two directions.

ALL Values are defined per cell.

The context menu for the properties tab contains the following options:

Connect Properties from Grid Updates the Source column with compatible properties from the static model. Additional properties are added as required.

Connect Sector Array The Sector Array can be connected to a property in the static model by specifying a property name in the source column. This static model property must use the Region property template. Furthermore, the sector name specified must match one of the class names for the property.

Options tab

The tables on the Options tab consist of parameters used for specific settings for the reservoir description. Here you define your grid. The first section, Grid type and dimensions, is duplicated from the General Settings view for ease of use, and is read-only in this view.

This section defines the dual porosity/dual permeability settings. Note that only one of the settings below may be specified for any single simulation run.

Dual Porosity (DUALPOR) Checkbox indicating the use of a dual porosity model.

Dual Permeability (DUALPERM) Checkbox indicating the use of a dual porosity model with inter-block matrix to matrix flows calculated as well.

Dual Porosity using multiple-interacting-continua (MINC) Specify the number subdivisions for each matrix block.

Dual Porosity Model using the subdomain method (SUBDOMAIN) Specify the number of SUBDOMAIN divisions.

Important To use the Fault Seal Model or a Zone to Zone Transmissibility Multiplier Model in combination with different porosity systems, make sure you are using CMG's 2022.30 release version or newer.

Volume fractions (FRACVOL) Specify the thickness of the SUBDOMAIN divisions

The Rock Compressibility section defines the rock compressibility and pressure values.

MATRIX/FRACTURE

Pressure dependence of formation porosity/ Rock Compressibility (CPOR) Specify the rock compressibility value that will be used throughout the model.

Reference pressure for calculating the effect of rock compressibility (PRPOR) Specify the reference pressure for the rock compressibility, this is the fluid pressure.

Advanced Settings

A set of advanced options to control factors such as shape calculation methods and pinchouts.

Pinchout block thickness (PINCHOUT_TOL) Specify the minimum thickness required for a block to be removed from the simulation.

Pore Volume Cutoff (PVCUTOFF) Specify the pore volume which will cause a block to be considered null in the simulation.

CROCKTYPE tab

The CROCKTYPE tab is used to specify the rock type settings for the reservoir description. The settings available for simulation cases submitted to both the IMEX™ and GEM™ simulators are described below.

Parameters tab

Compaction irreversible (CIRREVERS) This checkbox controls the reversibility of the rock type. When checked, the rock behavior is irreversible.

Pressure dependence of formation porosity/ Rock Compressibility (CPOR) Specify the rock compressibility value that will be used throughout the model.

Reference pressure for calculating the effect of rock compressibility (PRPOR) Specify the reference pressure for the rock compressibility, this is the fluid pressure.

For simulation cases that will be submitted to the GEM™ simulator, you also have access to an additional section in the Parameters tab for specifying Palmer and Mansoori parameters when considering CBM in your simulation:

Poisson ratio (POISSR) Specify the Poisson's ratio to be used.

Young's Modulus (YOUNGM) Specify the Young's Modulus value to be used.

Strain at infinite pressure (STRINF) Provide a value for the sorption strain at infinite pressure.

Lanmuir pressure (PRESLN) Specify the critical desorption pressure.

Fracture permeability component (EXPPM) Specify the permeability attributed to fractures in the simulation.

Compaction Tables tab

When having more than one rock type, you need to specify this in the CROCKTYPE tab.

Use the Compaction Tables tab to define the rocktype. Note that the table is connected to the type selected in the parent view (the single column table in the left pane of the view).

Type Select from the drop down box the compaction/dilation type.

Pressure Define the maximum pressure.

Porosity Mult Define the porosity multiplier.

Horizontal Permeability Multiplier Define the horizontal permeability multiplier.

Vertical Permeability Multiplier Define the vertical permeability multiplier.

SECTOR tab

The SECTOR tab contains the definitions for sectors within the reservoir, which can be used to summarize reservoir activity. You can use sectors to read various values relating to the blocks that reside in the sector. The master table of the SECTOR view (located in the left pane) controls the active sector, while the table is used to define the sector itself.

I1, J1, K1 Define the beginning indices for each direction in the sector.

I2, J2, K2 Define the ending indices for each direction in the sector.

Other Reservoir Properties tab (STARS™ only)

The Other Reservoir Properties tab is available in the Reservoir Description view only while defining a STARS™ simulation case. You can define the reservoir properties for each rock type.

The master table for the view contains a row for each rock type. It contains the following columns.

Active Determines whether rock type is active. Inactive rock types are not written to the deck.

Name Name of the Rock Type.

Rock Type ID ID of rock type used in the deck.

Important Make sure you undertake the following rules before assigning the Rock Type ID. An error message is displayed if a rule is broken.

1. The Rock Type ID must have a value greater than or equal to 1.

2. The active Rock Type ID numbers must start with 1 and have values increasing by 1.

3. Active Rock Type ID must not have unique ID numbers.

This section is divided in to six sub-tabs, where you can enter the input parameters for formation rock compressibility, reservoir rock thermal properties and overburden heat loss options.

Rock Compressibility

Reference pressure for formation compressibility (PRPOR) Specify the non-negative value of the reference pressure for the formation compressibility.

Formation compressibility (CPOR) Specify the formation compressibility for the selected rock type.

Formation thermal expansion coefficient (CTPOR) Enter the thermal expansion coefficient.

Pressure-temperature cross-term coefficient (CPTPOR) Enter the pressure-temperature cross-term coefficient of the formation effective porosity. The input field is inactive if the CPORPD option is enabled in the next input field.

Enable input of pressure-dependent formation compressibility (CPORPD) Check the checkbox to enable using the input parameters to define the pressure-dependent formation compressibility. Enter the parameters values in the entry fields below. The CPTPOR option is disabled if this input is enabled.

Lower reference pressure Specify the lower reference value (PPR1) for pressure-dependent formation compressibility.

Higher reference pressure Specify the higher reference value (PPR2) for pressure-dependent formation compressibility.

Compressibility near higher reference pressure Specify the effective formation compressibility value (CPOR_P2) at the higher reference pressure.

Maximum allowed fractional increase in porosity due to pressure (PORMAX) Specify the maximum allowed fractional increase in porosity due to pressure. This value must be greater than zero and less than one. Typical values range from 0.10 to 0.20.

Other Specifications

Specify the interpretation of input porosity (PORINTERP) The input porosity can be interpreted in two ways:

Reference Porosity (REF) calculated at reference pressure (PRPOR) and temperature (TEMR). This is the default selection.
Initial Porosity (INIT) calculated at initial pressure (PRES or VERTICAL), and initial temperature (TEMR).

Specify the form of pressure and temperature variation of porosity (PORFORM) Specify the function of porosity with pressure and temperature. Select between Linear or Exponential option from the drop down menu. By default, the Linear option is selected.

Specify the volume constraint type (VOLCONST) There are two ways to specify the cell volume constraint type.

Select Rock if the rock volume is constant and the bulk volume changes with changes in pore volume. This option preserves the rock mass and also the rock heat capacity at given temperature. This is the default selection.
Select Bulk if the bulk volume is constant and the rock volume is variable which causes changes in the rock mass. Therefore, the rock heat capacity changes which can result in temperature variation in the formation.

Thermal Properties

Rock Heat Capacity (ROCKCP) Specify the coefficients used to calculate the heat capacity of the formation.

Volumetric heat capacity of solid formation Specify the volumetric heat capacity (ROCK_CP1) of the formation.

Temperature dependent coefficient Specify the value for the temperature dependent coefficient (ROCK_CP2). If this value is zero then the volumetric heat capacity value is used.

Thermal Conductivities (THCONMIX, THCONTAB or THCONANTAB) Specify the inputs for thermal conductivities of rock, solid and fluid phases in the fields below.

Specify the rule used to mix thermal conductivities of rock and phases (THCONMIX) Select one of the four options from the drop down menu. Based on the selected mixing rule, the thermal conductivities of rock, solid and fluid phases are used to calculate

Simple Based on volume-weighted mixing rule.
Log Based on logarithmic volume-weighted mixing rule.
Complex Specifies mixing of rock and phase thermal conductivities that accounts better for porous media inter-phase contact. This option accounts for small porosities (<1%) and preserves numerical stability since porosity values near zero can result in nonphysically high thermal conductivity values.
Temper This is an extension of the Complex option with an additional temperature correction. This option is considered invalid if you are using the temperature tables (THCONTAB or THCONANTAB) for calculating thermal conductivities.

Thermal conductivity of reservoir rock (THCONR) Specify the thermal conductivity of the reservoir rock formation.

Thermal conductivity of water phase (THCONW) Specify the thermal conductivity of the water phase in the reservoir.

Thermal conductivity of oil phase (THCONO) Specify the thermal conductivity of the oil phase in the reservoir.

Thermal conductivity of gas phase (THCONG) Specify the thermal conductivity of the gas phase in the reservoir.

Thermal conductivity of solid phase (THCONS) Specify the thermal conductivity of the solid phase in the reservoir.

Use temperature dependent table for thermal conductivity Use this option if you want to define the thermal conductivities of the reservoir rock, solid and fluid phases using temperature dependent tables. You can choose between Isotropic (THCONTAB) or Anisotropic (THCONANTAB) method. Depending on your selection, respective tab for THCONTAB or THCONANTAB is enabled for entering the data. By default, this option is empty and you must specify the thermal conductivities values above.

THCONTAB

On this tab, specify the temperature-dependent isotropic thermal conductivities of the all the phases in the reservoir in a table format. Note that this tab is enabled only if you have selected the 'Isotropic' option for calculating temperature dependent thermal conductivity in the Thermal Properties tab.

There are six columns to enter the data in the table along with a comments column. The temperature values are defined in the first column followed by the thermal conductivity values of all the phases and the reservoir rock. The maximum allowed number of rows is 30. If the values for solid phase are missing then the rock thermal conductivity values are used.

THCONANTAB

On this tab, specify the temperature-dependent anisotropic thermal conductivities of the all the phases in the reservoir in a table format. The thermal conductivities vary along the I, J and K directions and must be specified accordingly. Note that this tab is enabled only if you have selected the 'Anisotropic' option for calculating temperature dependent thermal conductivity in the Thermal Properties tab.

There are sixteen columns to enter the data in the table along with a comments column. The temperature values are defined in the first column followed by the thermal conductivity values for each phase (e.g., rock, gas, solid), defined in group of three columns for I, J and K direction respectively. The maximum allowed number of rows is 30. The values for solid phase are optional.

Heat Loss

The Heat Loss tab defines the heat loss directions, and the overburden and underburden thermal properties for the semi-analytical heat loss model.

Initial temperature of formation adjacent to reservoir (HLOSS) Enter the initial temperature value of formation adjacent to the reservoir.

Minimum temperature difference of start heat loss calculation (HLOSSDIFF) Enter the value of minimum temperature difference needed between grid cell temperature and initial temperature of adjacent formation.

Overburden (OVERBUR) If the heat loss model is defined with overburden then the thermal properties are applied to the outer grid block faces at the reservoir top.

Volumetric heat capacity of formation Specify the value for volumetric heat capacity of formation when defined with overburden.

Thermal conductivity of formation Specify the value for thermal conductivity of formation when defined with overburden.

Underburden (UNDERBUR) If the heat loss model is defined with underburden then the thermal properties are applied to the outer grid block faces at the reservoir bottom.

Volumetric heat capacity of formation Specify the value for volumetric heat capacity of formation when defined with underburden.

Thermal conductivity of formation Specify the value for thermal conductivity of formation when defined with underburden.

To define the Heat Loss model with OVERBUR and UNDERBUR, the Directional Heat Loss option below must be set to 'No'.

Directional Heat Loss

Use heat loss properties in I, J, K directions Use the drop down menu to select if you want to specify the thermal properties for direction. Select 'No' if you want to use the OVERBUR and UNDERBUR thermal properties to calculate the heat loss model. Once you select 'Yes (HLOSSPROP)' then the adjacent tab HLOSSPROP (IJK) is enabled where you can enter the thermal properties for each direction.

HLOSSPROP (IJK)

This tab is enabled when you select the directional heat loss option in the Heat Loss tab. There are three columns in the tab - first column shows the direction Type (+I, -I, +J, -J, +K, -K), and you specify the Volumetric Heat Capacity and Thermal Conductivity in the second and third columns respectively.