11 petrel simulation10.pdf

Simulation

Reservoir simulation is the study of how fluids flow in a hydrocarbon reservoir when put under production conditions. The purpose is usually to predict the behavior of a reservoir to different production scenarios, or to increase the understanding of its geological properties by comparing known behavior to a simulation using differentgeological representations. See physical principles for further information.

Petrel Reservoir Engineering supports the Schlumberger ECLIPSE family of simulators:

ECLIPSE 100 - 3-phase finite difference fully implicit black oil simulator. ECLIPSE 300 - 3-phase finite difference fully implicit black oil,compositional and thermal simulator. FrontSim - 3-phase black oil streamline simulator. INTERSECT - 3-phase finite difference fully implicit black oil, compositional and thermal simulator. INTERSECT is Schlumberger's Next Generation Reservoir

Simulator.

All the simulators read their input from ASCII keyword and binary files, and write binary files as output. Petrel generates these input files, manages different cases, and presents the results in graphical form.

See also:

ECLIPSE manuals and INTERSECT manuals

Overview of How to Set Up a Simulation Case

1. Build a grid and populate it with properties.2. (Optionally) scale up the structure and properties onto a coarser grid. See Upscaling. 3. Define or import well paths. See Well Design. 4. Define or import well completion events. See Well Completion Design. 5. (Optionally) define unique (

Overview

INTERSECT is the Schlumberger next generation reservoir simulator, developed in partnership with Chevron and combining the extensive simulator development experience and global oil and gas reservoir management expertise of both companies.

Recognizing today's tough economic oil and gas environment and the ever more complex reservoirs our industry is pursuing, there is considerable pressure on operators to increase production in existing fields and make judicious investments in new fields. The INTERSECT simulator has been designed to make field development planning and risk mitigation of larger and more complex fields more efficient - to provide greater certainty in your reserves estimation and management. One key objective was ensuring that the INTERSECT software architecture enables you to take full advantage of changes in computing systems and operating environments to meet simulation requirements for many years to come. At the same time, many E&P companies have proprietary knowledge for simulating their reservoirs, so we willbe expanding Ocean our open development platform to the INTERSECT software in subsequent releases to allow our clients to further customize their simulationmodels using their own proprietary technology and techniques.

Reservoir engineers will find the INTERSECT simulator much faster than the current generation of reservoir simulators on large and heterogeneous models, with theability to rapidly simulate tens of millions of cells and thousands of wells. Leveraging state of the art solvers and parallel processing technologies engineers will be able to history match and prepare field development plans for large and geologically complex fields, with complex local grid refinements and unstructured grids, using high resolution geological and geophysical data with minimal or no upscaling. The speed of INTERSECT simulator also enables iterative simulation runs in practical timescales. It supports sophisticated field management capabilities and will support simulation of all fluid types and recovery processes in a single simulator to support simulation requirements throughout the life of the field.

This general release in June 2011, supports black oil and compositional models, a conventional well model, thermal modeling for heavy oil processes (created as part of a joint development with TOTAL), and a multi-segment well model for complex wells. INTERSECT is fully optimized when leveraging parallel compute infrastructure and as such it is not intended to be run as a serial simulator. The front end and user environment for INTERSECT is Petrel Reservoir Engineering, which integrates the static and dynamic modeling process into a seamless workflow. However, for those wanting to use existing ECLIPSE data sets as input, a tool is also available whichtranslates ECLIPSE keywords into INTERSECT input.

Reservoir Applications Suited to INTERSECT

Large fields, requiring millions of grid blocks for representative modeling of geological detail Highly heterogeneous or complex reservoirs Simulation models using many or gradual local grid refinements for accurate representation of flows around complex wells. High geological uncertainties requiring history matching with multiple realizations

Strengths of INTERSECT

Leverages the power of multi-processor / multi-core hardware to reduce simulation run times Efficient solution methods for local grid refinements, gradual local grid refinements and unstructured local grids Excellent scaling on large parallel machines A single platform for black oil, compositional and thermal simulation

Example Reservoir Challenges Benefiting from INTERSECT

Simulating naturally fractured carbonate oilfield with a discrete fracture network Uncertainty management of a giant dry gas field Simulating SAGD process of 9 well pairs of an oil sand reservoir Field scale modeling of 25-pattern inverted 5-spot steamflood with fine geological detail

Workflows

Seamless integration with Petrel seismic-to-simulation software to preserve accumulated earth model knowledge built in the interpretation and modeling stage Reservoir engineer builds model, launches INTERSECT simulation and analyzes results all from Petrel interface Existing ECLIPSE simulations can be migrated to INTERSECT for simulation; ECLIPSE format output files can be analyzed with a post-processor

More detailed information about INTERSECT and its manuals can be found in the Appendix section of this help.

Copyright 2011 Schlumberger. All rights reserved.Schlumberger Private - Customer Use

General Information on Streamline Simulation

FrontSim is a streamline simulator. This numerical method first solves the pressure, then computes the streamlines and thereafter computes the changes in saturation along the streamlines. The equations for saturation are solved as several one dimensional problems along streamlines, as opposed to solving one large three dimensional problem. Consequently, FrontSim can be very fast and hence capable of handling grids with millions of grid cells.

For reservoirs where the movement of the fluids is mostly driven by the potential field induced by wells, FrontSim is particularly efficient. Examples include:

Water flooding. Highly heterogeneous reservoirs.

Since FrontSim can be run quickly on very large models it is also a good tool for:

Screening of geological models. Validation of up-scaled models.

Streamline Calculation

Given the fluid pressure in each of the cells, we can find the streamlines by selecting a number of so called starting points in the reservoir. Beginning at these starting points, we find the lowest pressure (or alternatively the highest) in close vicinity of the starting point, such as the steepest downhill we can find, and follow this downhill to the next point, etc. This process will eventually lead us to a producing well. When we have gone through this process for all the starting points, the reservoir should be covered by streamlines.

Streamline Representation

Since the streamlines describe the direction of flow at the moment in time that they are computed, they can be used as a computational tool to move the fluids along. The streamlines can be seen as a set of tubes representing the total reservoir volume and through which the fluids are moving. The tubes have exactly the samegeological properties that the underlying geological model has. This approach divides the fluid flow into a set of one-dimensional models and therefore reduces the

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problem to a computational simplicity that can have significant advantages. Since each streamline carries about the same volume, the density of the streamlines is an indication of the velocity of the fluid.

Streamline Simulation Advantages

The sequential process described above (solve pressure - move fluids along streamlines) constitutes one time step. An advantage with this approach is that the time steps can be very long and therefore the computational effort needed can be reduced.

The obvious advantage of a streamline method is the possibility it offers to do relatively quick simulations on large geologically and architecturally complex models. This is the main reason that the streamline method is a popular tool for validating upscaling methods, measuring uncertainty, screening and ranking different modelscenarios. Another advantage of the streamline method is the visual information it gives about the fluid flow pattern and connectivity in the reservoir. This can be used to study the effects of different well patterns on the flow, and to monitor which volumes, wells and boundaries support a specific well at any given time.

Streamline Time Dependency

Even though a streamline simulation can be significantly faster than standard simulations, it can still be a time consuming affair if we want to model in detail all physical properties available in FrontSim. Some of the most important time dependencies are discussed below.

Number of Cells

The size of the model represented by the number of cells, will impact the time it takes to compute the pressure and move the fluids along. For example, for a model with 1 million grid cells it might take up to several minutes to compute the pressure and move the fluids one time step, depending somewhat on the complexity of the fluid description and the computational speed of the processor.

Fluid Description

The fluid description will impact the CPU time. The fastest model will be a low compressible two-phase model (oil/water). The low compressibility will cause the pressure solution to be easier to solve and the requirement for time steps for accuracy is low. In addition, if the mobility and densities of the fluids are close, one time step might still result in a reasonably accurate simulation result.

Time Steps

The number of time steps and the length of each time step will influence both the result and the time it will take to achieve a result. As we introduce more detail in the fluid description, we also potentially introduce a need to use shorter time steps. Such a factor is gravity segregation. To be accurate, more time steps are required even though FrontSim will include the effect in a one time step solution.

Compressibility

Another factor is the compressibility introduced when using a three-phase oil/water/gas model. To achieve close to engineering accuracy, we will have to enable the gravity segregation and use many time steps. In addition, the non-linearity of the model will cause more computational effort per time step. Note that FrontSim'sstreamline concept will allow the user to use only one long time step (possibly years), even for this type of model, but the engineering accuracy defined by standard simulation will be degraded.

The resulting set of partial differential equations cannot be solved by any analytical means due to its typical complexity in geometry, rock property and fluid description. Instead, a so called numerical approximation is used. Many types of numerical methods are available to solve these equations. Most use some form of a finitedifference/volume method that divides the geometry into many small subsections called cells containing rock and fluid properties. These cells cover the whole domain and the fluid flow is represented as relationships between these cells. These relationships result in an equation system with a number of unknowns on the order of number of cells or higher. This equation system will have to be solved for every time step during the simulation. These methods might require very many small time steps, and because of this, a reservoir simulation process can be a very time consuming affair depending on the geological detail represented and fluid property modeled.


Making a Fluid Model



The Make fluid model process allows you to generate black oil fluid models from correlations and to create compositional and thermal fluid models.

Fluid models are used by the simulator to define how physical properties of the fluid such as density and viscosity vary with pressure and temperature. Fluid models may also define how the initial conditions in the simulator are to be calculated, by specifying the fluid contacts, pressure, and compositional variation with depth.

Petrel supports three types of fluid model:

Black oil: A black oil fluid model specifies values of physical properties of oil and gas in tables. Compositional: A compositional fluid model represents the hydrocarbon fluid by a set of components (typically 612 for reservoir simulation). An equation of

state is then used to determine the physical properties of mixtures of these components as a function of pressure and temperature and the properties of the individual components.

Thermal live oil: A thermal live oil model describes the fluid by a set of components, using K-values to define equilibrium. All types of fluid model can incorporate water, with its properties represented as a simple function.

The most reliable way to obtain this information is from a reservoir fluid study using bottomhole or reconstituted fluid samples. Experimental results are processed using a dedicated package such as Schlumberger PVTi. Fluid models created in this way can be imported into Petrel and used in simulations.

If laboratory data is not available, both types of fluid model may be created in Petrel from minimal data input. While you can create an equation of state in Petrel, you cannot tune it to match laboratory measurements for that, you need to use PVTi and import the resulting equation of state into Petrel.

Data for initial reservoir conditions may also be entered in the Make fluid model process. Together with the fluid properties and saturation functions, this allows determination of the initial fluid distribution in the reservoir.

The workflows are described in subsequent sections:

Black Oil Fluid Model Workflow Compositional Fluid Model Workflow Thermal Fluid Model Workflow


Black Oil Fluid Model Workflow

You can add new black oil fluid models, and update or delete existing fluid models. Once created the fluid model will appear in the Fluids folder on the Input pane. See Fluid Model (Settings) for details of the settings page.

How to Make a New Black Oil Fluid Model from Correlations

1. In the Processes pane, open Simulation and select Make fluid model to open the Make fluid model dialog. 2. Select Create new fluid model and enter the name for the new fluid model into the adjacent field. 3. Select Black oil from the Model type drop down.4. Most of the fields on the dialog can be filled in with default values by selecting an option from the Use presets list. 5. Select the phases required by clicking on the appropriate check boxes. 6. If you know the values for the model parameters, enter them into the appropriate fields.7. If you wish to use particular correlations rather than the defaults, select the correlations in the Gas, Oil or Water tabs. 8. To specify the initial reservoir conditions for the model, you can either drop in a contact set (in which case the initial conditions will be derived from it and a

region grid property will be created that maps the initial conditions to grid blocks) or you can enter a table of contact depths and pressures.9. Click OK or Apply to create the new fluid model.

How to Make a Fluid Model from a File Containing ECLIPSE PVT Keywords

1. If the ECLIPSE keyword file to be input does not have a unit system defined, Petrel will assume that the units in the keywords file are the same as the simulation unit system (as specified in the Project | Project settings | Units and coordinates). In this case make sure that the simulation units are set correctly before importing (you can change the simulation units system back again afterwards, if necessary).

2. If you do not already have a Fluids folder in the Input pane, create one by selecting Insert | New fluid folder. 3. Right-click the Fluids folder and select Import (on selection) ...4. Select your ECLIPSE keywords file from the Import file dialog and click Open. This can be either a complete ECLIPSE .DATA file or a .PVO file, as generated

by PVTi. Note that supplying the complete .DATA file is preferable, as it allows Petrel to correctly associate the fluids with any initial conditions present in the file.

5. A number of fluid models that correspond to the keywords in the file will be created under the Fluids folder.

How to Make a Black Oil Fluid Model from Tables

If you have black oil fluid pressure tables and other fluid data, you can enter them directly in Petrel:

1. In the Processes pane, open Simulation and select Make fluid model to open the Make fluid model dialog. 2. Select Create new fluid model and enter the name for the new fluid model into the adjacent field. 3. Select Black oil from the Model type drop down. 4. Select the phases required by clicking on the appropriate check boxes on the General tab. 5. On each of the Gas, Oil and Water tabs (depending on which phases you have):

a. Disable the Create tables from correlations option b. Enter the fluid density (or gravity), and for water the viscosity, formation volume factor, compressibility and viscosibility

6. On the Initial conditions tab, enter the contact details as required 7. Click OK8. On the Input pane, right-click the gas or oil phases and select Spreadsheet from the context menu. You can enter a table of formation volume factor and

viscosity against pressure and solution gas-oil ratio (for oil) or vaporized oil-gas ratio (for gas). 9. If you have a gas and oil phase, you can right-click an initial condition and select Spreadsheet from the context menu. You can then enter a table of solution gas-

oil ratio and/or vaporized oil-gas ratio against depth.

How to Update an Existing Fluid Model

1. In the Processes pane, open Simulation and select Make fluid model. This opens the Make fluid model dialog.2. Select Edit existing fluid model and choose the model from the drop-down list. 3. Change the model parameters as required.4. Click OK or Apply to update the fluid model.




Compositional Fluid Model Workflow

How to Import an Equation of State Fluid Model

1. If the keywords file does not have a unit system defined, Petrel assumes that the units in the keywords file are the same as the simulation unit system (as specified in the Project | Project settings | Units and coordinates dialog). In this case make sure that the units are set correctly (you can change the simulation units system back again afterwards, if necessary). Alternatively, insert the keyword FILEUNIT with either METRIC or FIELD as the argument at the beginning of the

keyword file, or import the fluid from a complete ECLIPSE .DATA file which already contains the fluid model. 2. If you do not already have a Fluids folder in the Input pane, create one by selecting Insert | New fluid folder. 3. Right click on the Fluids folder and select Import on selection. 4. Choose the file format ECLIPSE fluid model (Keywords) and choose the file. Click Open.5. Petrel imports the fluid model into the Fluids folder.

How to Review and Edit the Equation of State Parameters

CAUTION:Manual editing of the component and interaction parameters is possible, but you are strongly advised not to do so! Editing is best done in a specialist package such as PVTi.

1. Open the Make fluid model process. 2. Select Edit existing and choose the required fluid model in the drop down.3. The Components tab displays the list of components, and the parameters of each component, such as molecular weight, omega A, etc.4. The Interactions tab displays the binary interaction coefficients.

How to Insert a Sample

Samples defined in the keyword file using the keywords ZI, ZMFVD or COMPVD are imported with the fluid. Additional samples may be created in Petrel as follows:

1. Open the Make fluid model process. 2. Select Edit existing and choose the required fluid model in the drop down. 3. The Samples tab lists the samples defined and their compositions.

4. Click to add a sample. 5. Enter the data to define the sample.

Plotting Compositional Fluids

You must first define a sample.

1. Then, simply expand the sample and open a function window. 2. Tick either Phase envelope or Finger print plot.

Note: Computing a phase envelope takes a few seconds, so there will be a pause before the data is displayed.

How to Define Initial Conditions for Compositional Simulation

1. Open the Make fluid model process. 2. Select Edit existing and choose the required fluid model in the drop down. 3. Choose the type of initialization. The choices are Gas; Oil; Gas with varying Oil rim; Gas with constant Oil rim; Oil with undersaturated Gas cap; Oil with

saturated Gas cap; Super critical transition. Thermal fluids also support the Mixed Hydrostatic initialization type. These are described in detail in Initial Conditions (Compositional).

4. Define the parameters required, depending on the type of initialization: pressure, datum depth, gas-oil contact, oil-gas capillary pressure, water contact, water-oil capillary pressure.

5. Choose whether to define the reservoir temperature as a constant, from a user function, or from the temperatures defined on the samples. 6. Tick the samples to be used to define the compositional variation with depth.

How to Make a Compositional Simulation

Once imported or created, and initial conditions have been defined, compositional fluids are used in simulation just as black oil fluid models. Note, however, that you cannot include both black oil and compositional fluids in the same simulation. Also note that the simulator you select needs to support compositional fluids (ECLIPSE 300 or INTERSECT).

1. On the Define simulation case | Functions tab, you must remove the Black oil fluid model included by default and instead add a Compositional fluid modelfrom the list of available functions.

2. Then, you simply drop in the initial condition(s) exactly as you would for a black oil fluid.

Note: Although initializing the simulation by enumeration is now supported for compositional simulation, the initial compositions must be added as user keywords. Initial saturations, pressure and temperature can be added in the Grid tab.


Thermal Fluid Model Workflow

The Petrel workflow supports thermal live oil fluids. A thermal fluid is created in the same way as a compositional fluid, either by importing keywords from in ECLIPSE fluid model (Keywords) format, or from the fluid process.

How to Review and Edit a Thermal Fluid Model

1. Select the thermal live oil model from Edit existing. 2. From the General tab, select if the model has water. Select how the specific heat of components should be supplied. This will determine the columns of the

Components tab. 3. Fill out the Components tab, defining parameters such as reference density, along with K-value coefficients for each component. If you want to define K-values



using either KVWI or KVTABTn keywords, then the K-values in the component tab should be left blank at present and the necessary keywords inserted via the editor. Note: Fill in the K-values in this table if the fluid model is used with INTERSECT. This is similar to using the KVCR keyword in ECLIPSE. Unlike ECLIPSE, INTERSECT currently does not allow empty fields to be exported and defined by the keyword editor. If you still need to use KVTABTn approach, export dummyK-values, then change the INTERSECT model by editing the IXF file.

4. Fill out the Samples tab as described in Compositional fluid model workflow. 5. The Viscosity tab allows temperature-dependent viscosity to be defined in tabular form (equivalent to keyword OILVISCT for example) or functional form

(equivalent to keyword OILVISCF).Note: The correlation keyword OILVISCC is not yet supported. If you want to include this in your simulation model then the keyword must be inserted via theeditor.

6. Define Water properties if the option has been selected from the General tab. 7. Define Initial conditions as described in Compositional Fluid Model Workflow.

How to Make a Thermal Simulation

The thermal fluid that you have created should be added to a simulation in the same way as a compositional fluid model.

Note: Keywords are exported with the same precision as their associated template. This means that if you are using the TCRIT keyword rather than CVTYPE to indicate that a component is only in the gas phase then you will need to increase the precision of the temperature template to 6dp. For more information please refer to the ECLIPSE reference manual.


Make Fluid Model Dialog Settings

The Make fluid model process allows you to enter the parameters required to create a black oil fluid model based on correlations or a compositional or thermal fluid model. It also allows you to edit the phase properties and initial conditions of an existing fluid model that has been imported.

An area at the top of the process dialog gives you the option to create a new model or edit an existing model. Once you have selected to create a new fluid, you need to select which fluid model to create. You cannot convert between fluid models.

The Use presets button allows a selection of example fluids to be easily created. Note that these fluids are artificial - you should always obtain real fluid properties for a reservoir study by obtaining a fluid sample and carrying out a laboratory analysis.

The icon on any tab may change to a warning triangle . This indicates that some/all of the data on that tab is incomplete or in error. Move the mouse over the warning triangle icon and a tool tip will explain the problem.

When creating a black oil fluid, the following tabs may be used:

General Gas Oil Water Initial Conditions (Black Oil)

When creating a compositional fluid, the following tabs may be used:

General Components Interactions Samples Water Initial Conditions (Compositional)

When creating a thermal live oil fluid, the following tabs may be used:

General Components Samples Viscosity Water Initial Conditions (Compositional)

The units displayed in the make fluid model process follow that set for the project at Project > Project settings... > Units and coordinates.


General

This tab is used for all fluid types, but looks different for the different types.

Black Oil



Phases Use the tick boxes to enable or disable the gas, oil and water phases.

Known separator conditions If you know the temperature and pressure in the separator, select this checkbox and enter the values into appropriate fields. Some of the correlation methods use separator conditions as input. Providing this information will therefore give you more correlation methods to choose from.

Minimum and Maximum pressure Enter the lowest and highest pressure likely to be encountered during simulation. If the simulation pressure goes outside this range then the simulator will have to extrapolate the pressure tables, which may cause inaccurate results or convergence problems.

Temperature Enter the average reservoir temperature.

Reference pressure Enter the pressure at which properties should be calculated. Typically, this is the initial pressure of the reservoir, but may be the pressure at which properties were measured in the laboratory if preferred.

Compositional

Phases Use the tick box to enable or disable the water phase.

Equation of state Use the drop-down menu to select an equation of state. An equation of state is used to determine the physical properties of mixtures of components as a function of pressure and temperature and the properties of the individual components.

Thermal

Water Use the tick box to enable or disable the water phase.

Specific heat of components Use the drop-down to select how the specific heat of components is defined. This will customize the Components tab.


Make Fluid Model: Water tab



Salinity Enter the salinity of water present for the model. This is in grams of solids per million grams of liquid (ppm). This option is available only if a water phase has been selected for the model. Alternatively the option to create tables from correlations can be deselected and the Density, Viscosity, Formation volume factor, Compressibility and Viscosibility can be entered directly. After clicking apply, the calculated properties are shown grayed out.

Create tables from correlations Enable this option if you wish to create new water property tables from correlations. This option should be disabled if you have imported the fluid table -otherwise the table will be overwritten when you click Apply. You can either leave each setting as (default), in which case the correlation is selected automatically by Petrel, or choose a named correlation from each drop-down list. Note that some combinations of correlations are not compatible. If you choose non-compatible correlation methods, Petrel gives a warning message and selects correlations that are compatible instead. For more information about the correlations available, please see PVT Correlations. The correlations used are recorded on the Statistics tab of the created fluid model's settings.


Make Fluid Model: Gas tab

Gas gravity, Gas density Enter either the density or specific the gravity of the gas relative to air. The gas density or gravity is required also when there is no gas phase present as long as an oil phase is present. All other options on this tab will be disabled if a gas phase is not present.

Vaporized gas/oil ratio This option is available only if the model is dry gas. The number entered is used to set a constant concentration of vaporized oil.

Create tables from correlations Enable this option if you wish to create new gas property tables from correlations. This option should be disabled if you have imported the fluid table -otherwise the table will be overwritten when you click Apply. You can either leave each setting as (default), in which case the correlation is selected automatically by Petrel, or choose a named correlation from each drop-down list. Note that some combinations of correlations are not compatible. If you choose non-compatible correlation methods, Petrel gives a warning message and selects correlations that are compatible instead. For more information about the correlations available, please see PVT Correlations The correlations used are recorded on the Statistics tab of the created fluid model's settings.

Table entries Controls the size of the tables that are generated; this approximately corresponds to the number of pressure points used.

Known impurities If you know the levels of impurities in gas, select this checkbox and enter the fractional value concentrations of hydrogen sulphide, carbon dioxide and nitrogen for the mixture. A value of 1 represents 100%. The total fraction of gas currently allocated to impurities is included in the Total components value shown in the



Known gas composition category. Known gas composition

If you know the composition of the gas, select this checkbox and enter the fractional value concentrations of each component up to a carbon chain length of six. You can also enter a value for all components with a chain length of seven or higher. A value of 1 represents 100%. The Total components value shows the total fraction of gas, including impurities, currently allocated; this value should be equal to 1 when all components have been entered.

C7+ characterizationEnter the molecular weight and specific gravity for the C7+ pseudo-component.


Make Fluid Model: Oil tab

Oil gravity, Oil density Enter the density or API gravity of the oil present. If no oil phase is present in the model, but a gas phase is, then the oil density or gravity is still required. All other options on this tab will be disabled.

Solution gas/oil ratioIf you know the ratio of dissolved gas in oil for the model (in standard cubic meters per standard cubic meter), select this option and enter the value. Alternatively, you can enter the bubble point pressure of the oil. If the corresponding bubble point pressure is less than the minimum reservoir pressure specified on the General tab, meaning that the reservoir can never go below the bubble point, then a dead oil fluid will be created; otherwise a live oil fluid will be created.

Bubble point pressure If you know the pressure at which bubbles of gas will form within the oil at the ambient temperature for the model, select this option and enter the pressure.Alternatively, you can enter the solution gas/oil ratio. If this pressure is less than the minimum reservoir pressure specified on the General tab, meaning that the reservoir can never go below the bubble point, then a dead oil fluid will be created; otherwise a live oil fluid will be created.

Create tables from correlations Enable this option if you wish to create new oil property tables from correlations. This option should be disabled if you have imported the fluid table -otherwise the table will be overwritten when you click Apply. You can either leave each setting as (default), in which case the correlation is selected automatically by Petrel, or choose a named correlation from each drop-down list. Note that some combinations of correlations are not compatible. If you choosenon-compatible correlation methods, Petrel gives a warning message and selects correlations that are compatible instead. For more information about thecorrelations available, please see PVT Correlations. The correlations used are recorded on the Statistics tab of the created fluid model's settings.

Table entries Controls the size of the tables that are generated; this approximately corresponds to the number of pressure points used.


Initial Conditions (Black Oil)

In this tab you can define the initial conditions in the reservoir that the simulator uses to calculate the pressure and phase saturations in every grid block duringinitialization. Each fluid region in the reservoir may contain a number of different, unconnected initial condition regions. For each region you must specify a reference depth and corresponding pressure, gas-oil contact depth and water contact depth (depending on which phases you have). In the Define Simulation Case Process you canassociate each of these initial condition regions with a region of the grid.



There are two ways you can define your initial conditions:

Define from contact set Define in table

Define from Contact Set

If you have an existing contact set, you can enable the Use contact set check box and drop in the contact set from the Petrel Models pane. There are two ways of defining contact sets:

Typing in the contacts For contact sets created from contact depths entered by the user, the Make fluid model process creates an initial condition region for each distinct set of contacts in the contact set.

Dropping in a contact surfaceFor contact sets created from surfaces, the Make fluid model process discretizes the contact surfaces into regions with similar values and creates an initial condition for each unique combination of contact depths. The datum depth and pressure are defaulted, if it is not defined in the contact set, and a discrete grid property, named after the contact set, is created that maps the initial conditions regions to the grid blocks.

You need to define the following:

Target number of initial conditions Enter the target number of initial conditions that you would like to represent the spatial variation in the contact surfaces. This parameter is ignored if the contact set was created from user entered contact depths. If separate sloping contacts are specified for different zones or segments, then this target is applies separately to each. So for example, if the number of bins = 5, and there is a different surface specified for the OWC in, say, zones Upper and Lower, then the process attempts to create 5 equilibration regions for zone Upper and 5 equilibration regions for zone Lower. Note this is a target number of bins; it may not be matched exactly.

Fill table from contact set The calculation of contact values from multiple sloping contact surfaces can take some time. Select this option to do the calculation now. The calculated set of initial conditions (if less than 500) is displayed in the table; otherwise the initial conditions and region property are calculated along with the fluid models when you select Apply or OK in this dialog.

Surface elevation This is zero, which is equal to mean sea level, by default. You can enter a different value for your field and this is used in the calculation of pressure as a function of depth (see Pressure and Datum depth below).

Define in Table

Disable the Use contact set check box and you can enter the details of each initial condition in a table. The table consists of a column for each initial condition region; columns can be added or removed using the usual Petrel table manipulation buttons. Each initial condition requires the following information:

NameEnter a name for the initial condition region.

PressureBy default the pressure is calculated using a pressure gradient of 0.0981 bar/m over the depth given by (surface elevation - datum depth). To enter a specific pressure, tick the box next to the pressure field.

Datum depth By default the datum depth is set to the same depth as the first contact. To enter a specific datum depth, tick the box next to the field. Note that if you choose a datum depth that is not at the gas-oil contact (and you have a gas and oil phase) then you will need to enter a table of solution gas-oil ratio or vaporized oil-gas ratio against depth on the initial condition after the make fluid process has completed See How to make a fluid model from tables.

Gas-oil contact Enter the depth of the gas-oil contact (this is an elevation, so is normally a negative value). This option is present only if both oil and gas phases are selected.

Water contact Enter the depth of the gas-water or oil-water contact (this is an elevation, so is normally a negative value). This option is present only if water and gas or oil phases are selected.

Oil-gas and Water-oil Pc



Enter the capillary pressure at the contacts.


Components

The Components tab allows you to define which hydrocarbon components are present in the equation of state, and their physical properties.

Add a component using the , , or buttons. You can add many components at once using the button. Remove a component by selecting its row and clicking the

button.

For each component, in the second column, either:

Select an existing library component, such as CO2 or C1. All the other properties on the row will be automatically filled in from the component library.

Select 'user'. You must then enter a unique name for the component, and its molecular weight. You may then either fill in all the other properties of the component, or click the Fill table button: this will generate all the required component properties based on the supplied molecular weight.

Caution: if you change the equation of state on the General tab, you should delete the properties of user components and click Fill table again, since some of the correlations for the component properties depend on the choice of equation of state.

For characterization Petrel is using Kesler-Lee for both critical properties & Acentric factors. "Improved Predictions of Enthalpy of Fractions", Kesler, M.G., and Lee, B.I., Hydro. Proc. p 153-158, March 1976.

For the component library, Petrel is using the original PVTi library, but with molecular weight, density and boiling points taken from Katz and Firoozabadi: "Predicting Phase behavior of condensate/crude-oil systems using methane interaction coefficients", Katz, D.L., and Firoozabadi, A., SPE 6721, 1978


Interactions



The Interactions tab allows you to define the binary interaction coefficients (BIC) between pairs of components. The BIC modify the default component interactions to account for molecular polarity effects. They are normally tuned using a program such as PVTi to match laboratory experiments. It is not advisable to edit them in Petrel.

When creating an equation of state you should click the Fill table button to generate the default BIC for your equation of state. If any values of BIC are left undefined,they will be automatically generated when the process is run.

Caution: if you change the equation of state on the General tab, you should delete the BIC for all components and click Fill table again, since the default BIC depend on the equation of state.

For the two Peng Robinson EOS, the Interactions characterization is taken from: Katz & Firoozabadi: "Predicting Phase behavior of condensate/crude-oil systems using methane interaction coefficients", Katz, D.L., and Firoozabadi, A., SPE 6721, 1978


Samples

The Samples tab allows you to define composition of one or more samples of the fluid.

Add samples with the button. Remove a sample by selecting its row (click on the grey area at the extreme left of the row) and click the button.

Having added a sample, you may define some or all of the following attributes

Name The name of the sample, used to identify it on the input tree. This is required

Well Drop in the well from which the sample was collected. This is optional.

Well MD Specify the measured depth at which the sample was collected. This is optional.

DateDate on which the sample was collected. The default date can be set in Project | Project settings. This is optional.

PressurePressure in the reservoir at which the sample was collected. This is not used in any calculations and may be omitted, but if it is known you are recommended to enter it, as it may be useful in validating the sample: samples collected below the dew- or bubble-point pressure are less likely to be representative of the reservoir fluid.

Temperature



Temperature in the reservoir at which the sample was collected. If the sample is used to define an initial condition, this temperature may be used to define the reservoir temperature for simulation.

DepthThe elevation (negative TVD) at which the sample exists. This parameter is required, as it is used if the sample is used to define an Initial condition.

Having defined these sample attributes, scroll to the right and enter the sample composition. You can use CTRL-V to paste compositions from another application (e.g. Microsoft Excel). Compositions are entered in % and must sum to 100:


Viscosity

This tab is visible for thermal live oil fluids only. It allows you to define how viscosity varies with temperature in the simulation.

For each Phase in the drop down, select a viscosity Type - either Function or Table.

If Function is selected then coefficients A and B must be defined for each component. Petrel will write out a keyword such as OILVISCF.

If Table is selected then a column of viscosity versus temperature must be added for each component. Petrel will write out a keyword such as OILVISCT.

Note: Only oil and gas viscosity tables are supported in INTERSECT.


Initial Conditions (Compositional)

In this tab you can define the initial conditions in the reservoir that the simulator uses to calculate the pressure and phase saturations in every grid block duringinitialization. Each fluid region in the reservoir may contain a number of different, unconnected initial condition regions. In the Define Simulation Case Process you canassociate each of these initial condition regions with a region of the grid.



It is not possible to define a compositional initial condition from a contact set.

The following types of initialization are supported:

Gas The fluid is initially single phase gas.

Oil The fluid is initially single phase oil.

Gas with constant composition oil rim The fluid is a gas, with a constant composition oil rim. The composition in the gas zone will be specified by the user, and must include specifying a gas composition at the gas-oil contact. The simulator will set the composition throughout the liquid zone to the liquid composition that is in equilibrium with the gas phase composition at the gas-oil contact. As pressure increases with depth, this will be undersaturated.

Gas with varying composition oil rimThe fluid is a gas with an oil rim. The composition in both the gas and oil zones will be specified by the user, but the composition specified at the gas-oil contact must be a gas.

Oil with saturated gas capThe fluid is an oil, with a saturated gas cap. The composition in the oil zone will be specified by the user, and must include specifying a liquid composition at the gas-oil contact. The simulator will set the composition throughout the gas phase such that it is saturated, starting from the vapor composition in equilibrium with the liquid composition at the gas-oil contact.

Oil with undersaturated gas cap The fluid is a liquid with a gas cap. The composition in both the gas and oil zones will be specified by the user, but the composition specified at the gas-oil contactmust be a liquid.

Supercritical transition The fluid passes from vapor to liquid phase with increasing depth, without passing through a distinct gas-oil contact. The composition throughout the hydrocarboncolumn is specified by the user.

Mixed hydrostatic equilibration This option is only available for thermal simulations. The selected sample is used by the simulator to generate non-equilibrium initialization composition tables.

Note: If you are specifying multiple initial conditions, there are restrictions imposed on the types of initialization that may be combined in a single case. You cannot mix the undersaturated gas cap and/or varying composition oil rim, with the saturated gas cap and/or constant composition oil rim. Mixed hydrostatic initialization type cannot be mixed with any other type.

Depending on the type of initialization chosen, the following data are required:

PressureThe pressure in the reservoir at the datum depth. If the tick box is not checked, it will be calculated to give hydrostatic pressure at the datum depth.

Datum The elevation (negative depth) at which the initial pressure is defined. This is disabled, and automatically set equal to the gas-oil contact for all initialization types except gas, oil and supercritical.

Gas oil contact The elevation (negative depth) at which the fluid passes through a distinct phase transition. Disabled for gas, oil and supercritical initialization types.

Water contact The elevation (negative depth) of the water contact.

Water-oil capillary pressure The water-oil capillary pressure at the water contact.

Temperature type The method by which the reservoir temperature is defined. There are three choices:

Constant specify a constant temperature for the whole reservoir. Function drop in a user function from the input tree, giving temperature in the first column and depth in the second. Note that the units of depth and

temperature in the user function are assumed to be the default project units for the project unit system. Samples the temperature vs. depth will be taken from the temperatures specified on the samples.

Samples Each sample defined in the fluid is listed in depth order. Tick to enable the samples to use to define the composition for this initial condition.



Note: For initialization in INTERSECT please see the INTERSECT Reference Manual, section Reservoir Initialization and the Migrator Manual, Solution section.


Separator Modeling

The Separator modeling process allows you to create and edit models of fluid separators.

Separator models are used by the simulator to model fluid separator equipment. Modeling the stage conditions and flow between the stages allows the simulator to calculate the volumes and compositions of the produced fluids.

Separator models may be associated with the entire field, specific groups of wells, or even single wells. During the course of a simulation a separator can be modified (stages may be added or their conditions changed) to reflect real situations.

Petrel supports multi-stage pressure-temperature type separators. It does not support cycling of fluids back to previous stages - output fluids can only be directed to later stages or the stock tanks. It does not support gas plants.

Some simple examples (2- and 3-stage separators) are provided as templates.

Note: Separator modeling can only be used with compositional fluids.

A work flow to define a separator is described in Separator Modeling Workflow


Separator Modeling Workflow

You can add new separator models, and update or delete existing ones. Once created the model will appear under a Separators folder on the Input pane. See Separator Modeling Dialog Settings for details of the settings page.

How to Define a New Separator Model

1. In the Processes pane, open Simulation and select Separator modeling to open the Separator modeling process dialog. 2. Select Create new and enter the name for the new separator model into the adjacent field. 3. On the Stages tab you will see a table containing a single stage. Click the Append N stages to table button to add more stages. 4. Each row in the table represents a separator stage. Enter the operating pressure and temperature of each stage, and select the destinations of the liquid and

vapor outputs from that stage using the drop-down selection. Note that by default the liquid from each stage will be set to go to the input of the next stage, and the vapor from each stage will be set to go to the stock vapor tank. Liquid and vapor outputs from the final stage will always go to the appropriate stock tank.

5. By default the conditions of the final stage are standard conditions. These may also be changed to exact values, if you have them. 6. Example separator conditions are provided; you can select these by clicking the Use presets drop-down.. 7. If the separator you have defined should only be used with a particular equation of state you can set this by selecting the appropriate compositional fluid in the

Input tree and clicking the Surface EOS drop button to set it. 8. Click OK or Apply to create the new separator model.

How to Define a Separator Model from a File Containing ECLIPSE Keywords

1. If the ECLIPSE keyword file to be input does not have a unit system defined, Petrel will assume that the units in the keyword file are the same as the simulation unit system (as specified in the Project | Project settings | Units and coordinates). In this case make sure that the simulation units are set correctly before importing (you can change the simulation units system back again afterwards, if necessary).

2. If there is an existing Separators folder, right-click on it and select Import (on selection)... If there is no Separators folder, right-click on the Input tree and select Import (on tree)...

3. Make sure the Files of type: field is set to ECLIPSE fluid model (Keywords)(*.*) on the Import file dialog.4. Select your ECLIPSE keyword file from the Import file dialog and click Open. This should be a complete ECLIPSE .DATA file. 5. A number of separator models that correspond to the keywords in the file will be created under the Separators folder, in a sub-folder with the same base name as

the input file. Note that if the file contains separators which are modified during the simulation, sub-folders will be created to store all the time-varying versions of those separators.

Note: If the file contains the STCOND keyword this will be imported and exported as a single stage separator.

How to Update an Existing Separator Model

1. In the Processes pane, open Simulation and select Separator modeling. 2. Select Edit existing and choose the model from the drop-down list. 3. Change the model parameters as required. 4. Click OK or Apply to update the model.


Separator Modeling Dialog Settings

The Separator Modeling process allows you to enter the parameters required to create a separator model or edit an existing one. The existing separator models may have been created from the dialog or by importing from an ECLIPSE DATA file.

The Use presets button allows you to choose an example separator to be used as a template.

The icon on the Stages tab may change to a warning triangle . This indicates that some/all of the data on that tab is incomplete or in error. Move the mouse over the warning triangle icon and a tool tip will explain the problem.

The units displayed in the Separator Modeling process follow those set for the project at Project | Project settings... | Units and coordinates.




Making Rock Physics Functions

Petrel includes functions of saturation or pressure used in simulation that represent the physics of the fluids, the rock, or the interaction between rock and fluids. The

Make fluid model process creates the functions that represent the physics of the fluids. The Make rock physics functions process is used to create functions that represent the physics of the rock and the interaction between rock and fluids, enabling the creation of Saturation functions and Rock compaction functions.

Rock physics functions are shown in the Input pane in the Rock physics functions folder . The different types of functions have different icons.

Saturation Functions

Saturation functions are tables showing relative permeability and capillary pressure versus saturation.These tables are used to calculate:

the initial saturation for each phase in each cell; the initial transition zone saturation of each phase; fluid mobility to solve the flow equations.

Creating saturation functions using the Make rock physics functions process also generates curves for gas-oil and water-oil capillary pressure versus saturation. These

are set to zero by default. The relative permeability and capillary pressure curves are grouped together under a saturation function icon in the Rock physics functions folder.

Rock Compaction Functions

Rock compaction functionsare tables showing pore volume multipliers versus pressure, or a single rock compressibility value used by the simulator to calculate the pore volume change. Creating rock compaction functions also creates a transmissibility multiplier versus pressure curves. These are set to one by default


Make Rock Physics Function Process Steps

In Petrel you can add new, and update or delete existing rock physics functions. You can also manipulate the settings for a rock physics function, together with details for their component tables; for example, capillary pressure curves within a saturation function.

Once created the Rock physics function is placed in the Rock physics functions folder on the Input pane. The object settings are described in Make Rock Physics Functions Dialog Settings. The contents of these will depend on what type of function you are examining.

Making Rock Physics Functions

You can create a new rock physics function from ECLIPSE keywords or from correlations.

Making Rock Physics Functions from ECLIPSE Keywords

You can create a new saturation function or rock compaction function from a file containing the relevant ECLIPSE keywords:

How to Make a Saturation and/or Rock Compaction Function from ECLIPSE Keywords

Petrel assumes that if the units in the keywords file are not specified then they are the same as the simulation unit system as specified in the Project | Project settings... | Units and coordinates menu).

1. Make sure that the units are set correctly or defined in the file (you can change the simulation units system back again afterwards, if necessary). 2. If you do not already have a Rock physics functions folder in the Input pane, create one by selecting Insert | New rock physics folder. 3. Right-click on the Rock physics functions folder and select Import (on selection). 4. Select your ECLIPSE keywords file from the Import file dialog and click on Open.

A number of saturation functions and rock compaction functions are created in the Rock physics folder that corresponds to the keywords in the file (if present).

Note that saturation functions are stored in Petrel and exported as family 1 keywords (SWOF, SGOF) unless the run is gas-water. Family 2 keywords are imported and



converted, with points being added by linear interpolation as necessary.

Making Rock Physics Functions from Correlations

You can create both saturation functions and rock compaction functions from correlations.

How to Make a Rock Physics Function from Correlations

To create a new rock physics function by using follow the steps below:

1. In the Processes pane, open Simulation and select Make rock physics function. This opens the Make rock physics functions dialog. 2. Select the Saturation or Compaction tab. 3. Select Create new function and enter the name for the new saturation function into the adjacent field. 4. In the Table entries field enter the total number of points that will be used to create the relative permeability and capillary pressure saturation function or the pore

volume multiplier pressure function tables.5. Select the phases for the function by checking the appropriate boxes.6. For Saturation functions:

If you know the values for relevant saturation end points and Corey coefficients, enter them into the appropriate fields. 7. For Rock Compaction functions:

Select a correlation in the Correlation drop-down menu, for example Hall correlation. Select the rock type in the Rock type drop-down menu, for example Consolidated sandstone. Type in the average reservoir porosity into the Porosity value field. Or drop a porosity property for your grid into the Porosity property field. Enter the values for the remaining parameters into the appropriate fields: for the Hall correlation these are the reference, minimum and maximum pressure

and overburden gradient. 8. If you do not have parameter values, click on Use presets and choose the rock characteristics. Default values will be written into the parameter fields. 9. Click OK or Apply to create the new function.

Existing Rock Physics Functions

You can update and manipulate existing rock physics functions.

How to Update an Existing Rock Physics Function

If you have a rock physics function that was created in the Make rock physics function process, follow the steps below:

1. In the Processes, open Simulation and select Make rock physics functions. This will open the Make rock physics functions dialog. 2. Select the type of function from the row of tabs. 3. Select Edit existing function data and choose a function from the drop-down list. 4. Change the function parameters as required. 5. Click on OK or Apply to update the function.

How to Manipulate Function Details

You can view and manipulate the details of the individual tables within a rock physics function, that is of relative permeability and capillary pressure functions within saturation functions and of pore volume multiplier and transmissibility multiplier functions within rock compaction curves.

1. Right-click on the Rock physics functions folder in the Input pane and select Spreadsheet from the menu. You can select a function from the drop-down list and then modify the tables from here. You can also right-click on individual saturation or rock compaction functions or individual relative permeability or capillarypressure functions within a saturation function to access the tables.

2. Alternatively, you can open a Function window (select Window | New function window) and display a rock physics function by checking the visualize box that appears in front of its name.


Make Rock Physics Functions Dialog Settings

The following options are available:

Function tabsSelect either the Saturation or Compaction function tab to create or edit your chosen type of function.


Saturation Function Settings

For further information on creating or editing saturation functions see Make Rock Physics Function Process Steps.



Phases Select the check boxes corresponding to the phases present in the reservoir.

Use presets You can select rock characteristics from this drop-down list, and this will apply typical values for the parameters in the dialog. Alternatively, you can enter your own values for the parameters.

Table entries Enter the number of points to be used to create the relative permeability and capillary pressure saturation function plots. Higher numbers give more accuracy but will cause simulations to run more slowly.

Phase parameters Enter any known parameters for the three fluid phases. Note that any parameters that do not apply to your selected phase combination are shown in gray and you cannot enter values for these parameters. The parameters are:

Gas

Sgcr Critical gas saturation.

Corey Gas For values between Swmin and (1-Sorg):

where Swi is the initial water saturation. Cg is the Corey gas exponent.

Krg@Swmin Relative permeability of gas at Swmin (minimum water saturation) value.

Krg@Sorg Relative permeability of gas at the residual oil saturation value.

Oil

Sorw Residual oil saturation to water. Note that (1-Sorw) > Swcr

Sorg Residual oil saturation to gas. Note that (1-Sorg) > Swcr

Corey O/W For values between Swmin and (1-Sorw):

where Swi is the initial water saturation. Co is the Corey oil exponent.

Corey O/G For values between Swmin and (1-Sorg):

where Swi is the initial water saturation. Co is the Corey oil exponent. Kro@Somax: Relative permeability of oil at the maximum value of oil saturation.



Water

Swmin Minimum water saturation.

Swcr Critical water saturation. This must be greater than or equal to Swmin (minimum water saturation).

Corey WaterFor values between Swcr and (1-Sorw):

where Cw is the Corey water exponent. Krw@Sorw: Relative permeability of water at the residual oil saturation value. Krw@S=1: Relative permeability of water at a saturation value of unity+

Oil-Water Capillary Pressure

These options generate a capillary pressure function using a correlation for mixed-wet reservoir rock from the simple power-law form of Brooks and Corey (Brooks, R.H. and Corey, A.T.: "Properties of Porous Media Affecting Fluid Flow," J. Irrigat. Drainage Div., Proc. ASCE Vol 92, No. IR2, 61.)

Max Pc Maximum capillary pressure.

Sw@Pc=0 Water saturation when the capillary pressure is zero.

Bro/Cor ao Pore size distribution for oil.

Bro/Cor aw Pore size distribution for water.


Rock Compaction Functions

For further information on creating or editing rock compaction functions see Make Rock Physics Function Process Steps.

Use presets You can select rock types from this drop-down list, and this will apply a typical choice of correlation and values for the parameters in the dialog. Alternatively, you can enter your own values for the parameters.

Table entries Enter the number of points to be used to create the rock compaction table function plots. Higher numbers give more accuracy but will cause simulations to run more slowly. At export you will have the option to export the rock compaction behavior (to some simulators) either as tables or as a single rock compressibility value.

Minimum and maximum pressurePetrel uses these values as pressure bounds for the pore volume multiplier versus pressure function (rock compaction function) when the function is exported as a table or when it is visualized in the Function window.

Correlation Select the correlation you wish to use to generate rock compaction tables (pore volume multipliers). Imported as table correlation cannot be selected: it is used to mark those rock compaction functions that have been created by importing the ECLIPSE ROCKTAB keyword.

Rock type Select the rock type from the available list; different correlations offer different selections. The combination of correlation and rock type determines the equation



used to calculate the rock compressibility Compressibility

Rock compressibility Cr at the reference pressure. You provide this value if you have selected User defined from the Correlation drop-down list, otherwise this is the result calculated from the correlation's equations and the other parameter values (see below).

Reference pressure The reference pressure applicable to your compressibility value.

Initial pressureInitial reservoir pressure for Knaap correlations.

Over burden gradient The overburden gradient for use in the Knaap correlations.

Porosity value Rock porosity. This can be specified as a single numerical value, or a porosity property from a grid may be dropped in here. The mean value of porosity will be used in the correlations. If a region property was selected, then the average porosity in each region will be used for that region's rock compaction function.

Depth valueThe reservoir depth must be supplied if the rock porosity is specified as a numerical value. If a porosity property is dropped in, then the depth will be calculated as the mean depth of the grid from which the porosity comes. If a region property was selected, then the average depth of the grid in each region will be used for that region's rock compaction function.

Region property If there are integer valued properties in the same folder as a porosity property dropped in above, then they will be listed in this drop-down list. All cells with the same property value form a region of the grid, and a separate rock compaction function is created for each region. Note that sets of rock compaction functions created using a region property can only be edited together, as a set of siblings.

Rock compaction equations

The following equations are used.

Newman

For Newman: is porosity

Unconsolidated sandstones

Consolidated sandstones

Consolidated limestones

Hall

For Hall: is porosity, Pa is the rock reference pressure and



Knaap

For Knaap: is porosity, Pa is the rock reference pressure, Pi is the initial rock pressure and




Thermal Boundary Conditions

Thermal boundary conditions allow heat loss to the overburden, underburden and sides of the reservoir to be modeled in a thermal simulation.

How to Create a Thermal Boundary Condition

1. Make one or more closed polygons using the Make/edit polygons process (we recommend using the 2D window for this, since you will need to click outside the reservoir).

2. Open the Thermal boundary condition process. 3. Drop in the polygons. 4. For each polygon choose the settings which define the connections to the grid. The controls are identical to those in the Make aquifer process.5. Set the properties of the boundary condition.




Thermal Boundary Condition Settings

In this dialog you can define and connect thermal boundary conditions to the grid.

Connections In this tab you define how the boundary condition is connected to the grid. The settings here are identical to the Make aquifer process, and described on the Connections tab help page.

Properties In this tab you enter the properties of the thermal boundary condition. These are equivalent to the ROCKPROP keyword.


Aquifers

Aquifer modeling is a method of simulating large amounts of water (or gas) connected to the reservoir whereby it is not essential to know how the fluid moves in it, but rather how it affects our reservoir.

There are several aquifer models: numerical, Carter Tracy, Fetkovich, constant flux, constant pressure (gas or water) and rainfall. Each aquifer model has its own set of parameters and can be connected to the grid in different directions: top down, bottom up, grid edges and/or fault edges. To have better control over which cell needs to be connected, a series of options can be used to limit the vertical extent and to restrict the connections to filtered cells only. A compass control furthermore helps the user to be more selective with grid and fault edge drive directions.

How to Create an Aquifer

1. Make a closed polygon using the Make/edit polygons process (we recommend using the 2D window for this, since you will need to click outside the reservoir). 2. If the aquifer is to be connected to a local grid set for later simulation tick the local grid set in the Model tree to make the local grid set visible in the 3D window. 3. Open the Make aquifer process. 4. Drop in the polygon. 5. Choose the direction. 6. Set the aquifer type and properties.


Make Aquifer Dialog Settings

In this dialog you can define and connect aquifers to a given simulation grid.


Create new This option allows you to make a new aquifer.

Edit existing This option allows you to modify an existing aquifer.

Both options allow you to select one of the following aquifer models: numerical, Carter Tracy, Fetkovich, constant flux, constant pressure gas, constant pressure/head water and rainfall.



INTERSECT supports the following aquifer models: numerical, Carter-Tracy, Fetkovich, and constant flux. Aquifer salinity and tracer options are not available in INTERSECT. For more information about aquifer modeling, please refer to INTERSECT Technical description manual, chapter Aquifer modeling.

You can also:

1. Define or edit the aquifer connections. 2. Define or edit the aquifer properties.


Connections tab

In this tab you define the aquifer's connection to the grid. Connections are independent of the aquifer model; therefore the information here does not change according to any changes to the aquifer model.

If an aquifer is connected to a local grid set, aquifer connections are recalculated when that local grid set is edited or deleted.




Area of interest Defines the area of interest to connect the aquifer, based on closed polygons. Use the blue arrow to drop closed polygons, and use the button below the blue arrow to remove polygons from the list. Direction, Vertical extent and Filter options can be different for each polygon when more than one polygon is used to define the area of interest. Numerical aquifers do not connect to local grid cells. Local grid cells within polygons will be ignored for numerical aquifers.

Direction Defines the aquifer drive direction. You can select one or more of the following options:

Top down: connected to the top cells of the grid. Bottom up: connected to the bottom cells of the grid. Grid edges: connected to the external side of the cells. Fault edges: connected to the cells along a fault which has at least part of the fault face not connected to any grid cell (see picture below).

Vertical extent Optional setting which allows you to select top and/or bottom limit of the connected cells. You can use a fixed depth, a surface or a contact. When a surface is used as the top and/or bottom limit make sure that all the cell centers of the cells concerned are within the aerial extent of surface. This can be a problem with sloping grid and fault edges. If need to make the surface bigger by using the Make/edit surface process.

Filter Optional check-box which allows you to connect only the filtered cells. If this option is not checked, the whole grid is used. Create a filter by right-clicking on a Filter folder (Input tree) or property (Models tree) and selecting Create 1D filters. Note that cell selection is based on the cell center of the top layer, even if thatlayer is not in the filtered cells; then it checks which of those cells fall in the filtered selection.

Connected Faces Visualization in 3D Window

Once you fill in the relevant data in the Connections tab and apply the changes, the connected faces are generated and stored under the Aquifers folder for the grid.

You can visualize the connected faces in a 3D window by ticking the aquifer checkbox.


Properties tab

In this tab the aquifer properties are defined. Each aquifer model requires a different set of properties; hence this tab changes according to the aquifer model.

The parameters needed for the different aquifer models are explained in the links below.

Numerical aquifer Carter Tracy aquifer Fetkovich aquifer Constant flux aquifer Constant pressure gas model Constant pressure/head water aquifer Rainfall aquifer

For detailed information about these models, please refer to the "ECLIPSE Technical Description" manual, Chapter 4: Aquifer Modeling Facilities.


Numerical Aquifer

This aquifer model is represented by a cell, or set of cells, where only the first cell is connected to the reservoir. The set of cells defining the aquifer are connected together in the following order: Reservoir cell 1 cell 2 ... cell (n-1) cell n.

Numerical aquifers do not connect to local grid cells. Local grid cells within polygons that define the area of interest will be ignored for numerical aquifers.

To establish this aquifer model the following properties need to be defined:



Number of cells Select the number of cells to model the numerical aquifer.

Fluid model When selected, this option allows you to drop a fluid model using the blue arrow and take the water properties from it. If unchecked, it will take the water properties based on the PVT region number (PVTNUM) of the cell.

Saturation function This option allows you to drop a saturation function using the blue arrow. If unchecked it will use the saturation function based on the saturation function number (SATNUM) of the cell.

Transmissibility multiplier You can change the calculated transmissibility using this multiplier. This can be useful, for example, when performing history matching.

Numerical Aquifer Cells

Each numerical aquifer cell needs the following properties:

Equilibrium Select this radio button to have the initial pressure in hydrostatic equilibrium with the reservoir.

Initial pressure Select this radio button to type the initial pressure at datum depth.

Datum Check the box to specify the aquifer reference depth. The default value is cell depth.

Permeability Aquifer permeability. This parameter cannot be defaulted.

Porosity Check the box to specify the aquifer porosity. The default value is cell porosity.

Cross sectional area This value can be larger than the cell cross-sectional area.

Length This value can be larger than the cell length.

The aquifer cell volume is calculated using porosity, cross-sectional area and length.


Carter Tracy Aquifer

The Carter Tracy aquifer model is a simplified approximation to a fully transient model, which avoids the need for superposition. The model uses tables of dimensionless time versus a dimensionless pressure influence function. The default table is for an infinite reservoir with constant terminal rate as given by Everdingen and Hurst.

The list of properties needed to define this aquifer model is as follows:



Datum Aquifer reference depth.

Permeability Aquifer permeability.

Porosity Aquifer porosity.

Total compressibility



Aquifer total (rock and water) compressibility. External radius

Aquifer external radius. Thickness

Aquifer thickness. Angle of influence

The angle subtended by the aquifer boundary from the center of the reservoir, measured in degrees. Salt concentration

Initial salt concentration. This value is relevant either for brine option, or if salt-sensitivity option in polymer flood is activated, otherwise it is ignored. Fluid model

Use the blue arrow to drop a fluid model from which the aquifer will take the water pressure properties.Influence function

Use the blue arrow to drop a user function. The user function is a dimensionless time and pressure table.


Fetkovich Aquifer

The Fetkovich aquifer model uses a simplified approach based on a pseudo-steady-state productivity index and material balance relationship between the aquifer pressure and the cumulative influx.

The properties needed to define this aquifer model are as follows:



Datum Aquifer reference depth.

Volume Initial aquifer water volume.

Total compressibility Aquifer total (rock and water) compressibility.

Productivity index Aquifer productivity index, which is total influx rate per unit pressure difference.

Salt concentration Initial salt concentration. This value is relevant either for the brine option, or if the salt-sensitivity option in polymer flood is activated, otherwise it is ignored.

Fluid model Use the blue arrow to drop a fluid model from which the aquifer will take the water pressure properties.




Constant Flux Aquifer

A constant flux aquifer model has its water flux specified directly by the user, instead of being calculated by an analytic aquifer model. The water flux can be modified over time by entering the corresponding values in the Time tab.

The properties needed to specify this aquifer are:

Spatially constant flux Select this radio button to specify a constant inflow value.

Spatially variable flux Select this radio button to use an inflow map.

Total area flux Select this radio button to specify water inflow rate for total area.

Unit area fluxSelect this radio button to specify water inflow rate per unit area.

Flux Aquifer water inflow rate per unit area of connected cell face. It can be either a value (constant) or a map (variable). When using a map, make sure it covers all the simulation grid area.

Number of bins This setting is only required when using spatially variable flux and it is the number of regions into which you want to divide the flux map. It uses the minimum and maximum values of the whole map to perform the calculation; if the map is too large compared to the simulation grid area the region values may not be representative, so it may then be better to use a smaller map. When selecting Apply, a grid property is generated, and its name follows the convention: "[aquifer name] regions using [map name]".

Salt concentration The initial salt concentration. This value is relevant either for the brine option, or if the salt-sensitivity option in polymer flood is activated, otherwise it is ignored.

Temperature Check this box to specify the aquifer temperature.



Time

This tab allows you to change flux and salt concentration properties over time. If no values are entered here it is assumed that the aquifer does not change during the simulation.

RegionsThis tab is activated only when using spatially variable flux. This tab sho

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