ParaGeo geometry generation

 

In this manual page the datafile for generation of the ParaGeo geometry and ParaGeo reservoir mesh in IX format will be described. Note that in this example the ParaGeo geometry is generated simultaneously to the IX .bin file. There may be cases however in which the starting .geo file is already created and only the .bin file need to be generated. At the end of this page after the results section some considerations for such case are provided.

 

Basic Set Up: Data file description

The initial data file for the project is: IX_002\Generation\IX_002_gen.dat.   The basic data includes:

1Units data structure defining the units for the simulation

2Geometry_set data defining the boundaries and the different sediment volumes of the model.

3Stratigraphy data (Stratigraphy_definition and Stratigraphy_horizon data structures) to identify the top surface of the model.

4Group_data for two groups (reservoir and shale) and Group_control_data to define geomechanical field active for both groups.

5A Material_data and Fluid_properties data structures defining the reservoir and shale material properties.

6Support_data defining the displacement and pore pressure constrains.

7Mesh control (Mesh_control) and Structured mesh generation data (Structured_mesh_data and several Structured_line_set) defining a the mesh for the problem.

8Time_scaling_data defining a target optimal time step of 0.5E-4 years.

9Damping_global_data defining bulk viscosity damping.

10Control data (Control_data) for two stages defining:

(a)  Incremental solution algorithm (Type 1),

(b)  Maximum number of time steps of 1. We only require to run a single time step as the objective is to generate the geometry and mesh for the simulation.

(c)  Duration time of t=1.

(d)  Factor of critical time step = 0.5,

(e)  Plot file output every 0.2 time units,

(f)  Plot file output at the end of the stage,

(g)  Screen message output every 1000 mech steps,

11Util_write_geometry data to output the .geo file

12Reservoir_coupling_data used to request output of the .bin mesh file for IX.

13Geometry data (nodal_data, Geometry_line , Geometry_surface and Geometry_volume ) for definition of the 3D geometry.

 

The Units data structure is used to define the units for the simulation. Definition of the units generally allows to always define density in Kg/m3 regardless of the units adopted and the code will automatically convert the gravity loafing accordingly.

 

Data File

 

 

* Units  

! ---------------------------------

 Length                   "m"

 Stress                   "Pa"

 Time                     "s"

 Temperature              "Celsius"

 Permeability             "m^2"

 Density                  "Kg/m^3"

 

 

1The units for the simulation are defined.

 

Geometry_set data can be used to group a set of geometry entities and provide a name for the set. Then the defined Geometry_set may be used to assign boundary conditions, loads, etc.

 

Data File

 

 

* Geometry_set                    NUM=1

! ----------------------------------------

 Name                     "Base"

 Surfaces                         IDM=4

   1  2  3  4

 

* Geometry_set                     NUM=2

! ----------------------------------------

 Name                     "Top"

 Surfaces                         IDM=4

   13  14  15  16

 

 

(...)

 

 

* Geometry_set                    NUM=8

! ----------------------------------------

 Name                     "Shale"

 Set_type                 "Group"

 Volumes                          IDM=11

   1  2  3  4  5   7   8  9  10  11

 12

 

 

1.Eight geometry sets are defined:

a.Six geometry sets defining the surfaces which constitute the boundaries of the model

b.Two geometry sets defining the volumes that constitute the reservoir and shale sediments.

 

Stratigraphy data is required for this problem as geostatic data with depth dependent properties is used. Only the minimal data required to define the top surface (from which the code will be able to obtain depth) is defined.

 

Data File

 

 

* Stratigraphy_definition

! ----------------------------------------

 Top_surface_horizon  "Top_surface"

 

 

* Stratigraphy_horizon NUM=1  

! ----------------------------------------

 Name          "Top_surface"

 Geometry_set          "Top"

 

 

1The units for the simulation are defined.

 

The Group_data data structure is compulsory and defines the properties for each geometry group.  Each group defines a region of the model domain with same properties. For this example these comprise:

1The name of the group.

2The element type.

3The material assigned to the group

4The type of porous flow

5The geometry sets defining each group.

 

Data File

 

 

* Group_data                       NUM=1

! ----------------------------------------

 Group_name               "Reservoir"

 Element_type             "Hex8"

 Material_name            "Reservoir"

 Porous_flow_type         2

 Geometry_set             "Reservoir"

 

 

* Group_data                       NUM=2

! ----------------------------------------

 Group_name               "Shale"

 Element_type             "Hex8"

 Material_name            "Shale"

 Porous_flow_type         2

 Geometry_set             "Shale"

 

 

1Two groups sre defined using the HEX8 element (8 noded hexahedral 3D elements).  

2The groups are named "Reservoir" and "Shale" respectively

3The materials assigned are also named "Reservoir" and "Shale" respectively (note that the material name may be different than the group name).

4The simulation will be performed using the porous flow type number 2 (drained conditions with prescribed pore pressure).

5The geometry sets defining the groups are assigned.

 

The Group_control_data  data structure is compulsory and defines:

1The group number for each group in the problem, where each group (Group_data) relates to a region with specific properties; e.g. regions with different material assignments, individual stratigraphy layers, etc.

2Whether the group is active or inactive in the fields; i.e. geomechanical, porous flow, thermal, that are being solved.

 

Data File

 

 

* Group_control_data

! ---------------------------------

 Group_numbers                 IDM=2

   1  2

 Active_geomechanical_groups   IDM=2

   1  1

 

1.The two groups present in the simulation are defined with the geomechanical field active (value of 1).

 

Two Material_data structures are defined(one for reservoir, one for shale). Also two Fluid_properties data structures are defined (one for water, one for mixture of foil and water with less density). Note that the material properties specified in this file are purely elastic as we are only interested in generating the geometry and mesh.

 

Data File

 

 

* Material_data NUM=1

! ---------------------------------

 Material_name                  "Shale"

 Grain_stiffness                      30000E6   ! Pa

 Grain_density                         2710.0   ! Kg/m3

 Porosity                                0.35

 Elastic_model_type                         1   ! Isotropic Elasticity

 Elastic_properties  IDM=2

  /Young's Modulus (E)/            1000.0E6   ! Pa

  /Poisson's Ratio (V)/                 0.25

 Fluid_saturation                         1.0

 Singlephase_fluid_name             "Water"

 

* Material_data NUM=2

! ---------------------------------

 Material_name                  "Reservoir"

 Grain_stiffness                      30000E6   ! Pa

 Grain_density                         2710.0   ! Kg/m3

 Porosity                                0.15

 Elastic_model_type                         1   ! Isotropic Elasticity

 Elastic_properties  IDM=2

  /Young's Modulus (E)/            1000.0E6   ! Pa

  /Poisson's Ratio (V)/                0.25

 Fluid_saturation                        1.0

 Singlephase_fluid_name             "Mixture"

 

 

* Fluid_properties      NUM=1

! ---------------------------------

 Name                                  "Water"

 Fluid_type                            "Water"

 Density                                 1000 ! Kg/m3

 Stiffness                             2000E6 ! MPa

 

* Fluid_properties      NUM=2

! ---------------------------------

 Name                                "Mixture"

 Fluid_type                            "Water"

 Density                               944.00 ! Kg/m3

 Stiffness                             2000E6 ! MPa

 

1The two materials "Shale" and "Reservoir" are defined.

2Minimal data considering elasticity is defined (in this step we are only interested in generating the geometry and mesh). Therefore material properties will be discussed when relevant.

3Shale material has assigned a fluid named "Water" whereas Reservoir material has assigned a fluid named "Mixture".

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1Fluid_properties for "Water" and "Mixture" are defined.

2Water density is set to 1000 kg/m3 whereas Mixture density is set to 944 Kg/m3.

3Water and Mixture stiffness are set to 2000E6 Pa.

 

 

The support data is used to define fixities in displacements and pore pressure fields.

 

Data File

 

 

* Support_data

! ------------------------------

 Displacement_codes  IDM=3  JDM=4

  /Set 1/  1  0  0

 /Set 2/  0  1  0

 /Set 3/  0  0  1

 /Set 4/  1  1  1

 Displacement_code_geom_set  IDM=2

  "Reservoir"

 "Shale"  

 Displacement_code_geom_ass  IDM=2        

   4  4  

 Pore_pressure_codes  IDM=1  JDM=2

  /Set 1/  0

 /Set 2/  1

 Pore_pressure_code_geom_set  IDM=2

  "Reservoir"

 "Shale"

 Pore_pressure_code_geom_ass  IDM=2

   2  2

 

 

 

1In ParaGeo the keywords Displacement_codes, Displacement_code_geom_set and Displacement_code_geom_ass are used in conjunction to define displacements constrains and assign them to any number of geometry sets.

2In Displacement_codes sets of displacement conditions that can be later assigned to geometry sets are created. They define whether displacements in X, Y and Z are prescribed (1) or free (0). In the present case 4 different sets are defined.

3In Displacement_code_geom_set geometry sets that will be assigned any of the DIsplacement_codes sets are listed. In the present case "Reservoir" and "Shale" will be assigned displacement codes.

4In Displacement_code_geom_ass the set number of Displacement_codes assigned to each of the geometry sets listed in Displacement_code_geom_set is defined. In the present case both "Reservoir" and "Shale" are assigned set number 4 which defines fixity in all directions.

5In ParaGeo the keywords Pore_pressure_codes, Pore_pressure_code_geom_set and Pore_pressure_code_geom_ass are used in conjunction to define pore pressure constrains and assign them to any number of geometry sets.

6Pore pressure code sets are defined. Pore pressure code sets define whether pore pressure is prescribed (1) or free (0) and can later be assigned to geometry sets.

7In Pore_pressure_code_geom_set geometry sets that will be assigned any set of conditions defined in Pore_pressure_codes are listed. In the present case "Reservoir" and "Shale" will be assigned pore pressure codes.

8In Pore_pressure_code_geom_ass the Pore_pressure_codes set number of  assigned to each of the geometry sets defined in Pore_pressure_code_geom_set is defined. In the present case both "Reservoir" and "Shale" geometry sets are assigned pore pressure code set number 2 so for both pore pressure will be prescribed.

 

 

Data for generation of the structured mesh is described here. The reservoir mesh

 

Data File

 

 

* Mesh_control_data

! --------------------------

 Generation_algorithm  1

 Mesh_generation_flag  0

 

 

* Structured_mesh_data  

! --------------------------

 Default_divisions  1

 List_structured_line_sets  IDM=7

   1  2  3  4  5  6  7

 

* Structured_line_set  NUM=1

! ----------------------------------

! Reservoir X divisions

 Lines  IDM=1

  1  

 Number_divisions    8

 Division_size_ratio 3

 

 (...)

 

* Structured_line_set  NUM=7

! ----------------------------------

 ! Overburden Z divisions

 Lines  IDM=1

   67

 Number_divisions    25

 Division_size_ratio 12

 

1The algorithm used for this simulation is set to 1  (i.e. structured mesh).

2Mesh_generation_flag is set to 0 (perform simulation). This is required as we are interested to run a single time step to generate and output a .geo file.

3Structured_mesh_data is defined with Default_divisions set to 1 (by default each volume will consists of a single element).

4Seven Structured_line_set are assigned by number in the Structured_mesh_data. Those will be used to define specific number of divisions for each line overwritting the default value of 1.

5The lines included in each Structured_line_set are specified.

6The Number_divisions controls the number of elements that will be generated for that line.

7The Division_size_ratio defines the ratio in size between the biggest and smallest elements in the line which are located at opposed line edges. For Structured_line_set NUM=1 for example line 1 (and any equivalent line) will be subdivided in 8 divisions (so 8 elements will be generated along those lines) and the size of subdivisions will progressively increase so that the last subdivision of the line is 3 times larger than the first one.

 

 

The mechanical step size is defined via Time_scaling_factors data structure. The Optimal_time_step keyword has been used. It is the most simple way of defining the mechanical time step size and is generally recommended. Using this method the mass scaling is computed automatically.

 

Data File

 

 

* Time_scaling_factors

! --------------------------------------

 Optimal_time_step              0.5E-04

 

1.An optimal time step of 0.5·10-4 time units is defined

 

 

 

Damping_global_data is defined in order to minimize dynamic oscillations in the solution.

 

Data File

 

 

* Damping_global_data

! ----------------------------------------

 Bulk_damping_model       "BulkViscosity"

 Bulk_damping_properties          IDM=1

  0.5  

 

 

1Bulk viscosity damping is selected for this case.

2A damping factor of 0.5 is defined.

3This value is generally recommended.

 

 

The current analysis considers a two simulation stages defined by their respective Control_data structures in which control data for the geomechanical field is provided.  For more information see Solution Control Data.

Note that only the first Control_data structure is described here.

 

Data File

 

 

* Control_data

! --------------------------------------

 Control_title               "Stage"

 Solution_algorithm                1   ! Incremental - transient

 Maximum_number_time_steps         1

 Duration                        1.0

 Displacement_norm_tolerance     0.1

 Target_number_time_steps      30000  

 Factor_critical_time_step       0.5

 Output_time_plotfile            0.2

 Output_frequency_plotfile        -1

 Screen_message_frequency       1000

 Output_frequency_restart         -1  

 

 

 

 

1Stage is named "Stage"

2The solution algorithm is set to number 1 ( i.e. Transient dynamic algorithm). This is the algorithm often used in non-coupled simulations.

3Stage duration is set to 1.0 time units

4Manixum_number_time_steps is set to 1 so a single time step will be considered and the stage will finalize.

5The factor critical time step is set to 0.5 so the time step used for the simulation will be  0.5 ·  0.5·10-4.

6Target_number_time_steps is set 30000. If defined it will take precedence in defining the time step size over the Optimal_time_step defined in Time_scaling_factors data structure.

7Information will be displayed on the screen (command prompt) every 1000 mech steps.

8A plot file is requested every 0.2 time units (Output_time_plotfile=0.2) and also at the end of the stage (Output_frequency_plotfile=-1).

 

Util_write_geometry is defined in order to output a .geo file.

 

Data File

 

 

* Util_write_geometry

! ----------------------------------------

 File_name   IX_002_geom.geo

 

1Definition of Util_write_geometry is required to output a .geo file.

2The output file name is specified.

 

 

Reservoir_coupling_data is defined in this case in order to output a .bin file with the IX equivalent ParaGeo mesh.

 

Data File

 

 

* Reservoir_coupling_data

! ----------------------------------------

 Groups    IDM=1

  "Reservoir"

 Units_list IDM=4

  "stress"  "length"  "temperature"  "density"

 Units  IDM=4

  "psi"     "ft"      "Rankine"      "lb/ft^3"

 Reservoir_coordinate_type   "Eclipse"  

 Reservoir_origin  IDM=2                

   381  762

 Surface_reference_level    0

 Output_ix_bin_file         1

 

1Only group "Reservoir" should be considered.

2The physical quantities and the corresponding units used in the IX simulation are defined.

3The coordinate system type adopted by the reservoir simulator is specified. In this case IX adopt the Eclipse system in which Z is positive downwards (so it is positively correlated with depth). This is used by ParaGeo to convert the coordinates of the mesh for the reservoir group created for mapping purposes.

4In Reservoir_origin the offset required for the ParaGeo reservoir to match IX reservoir location is specified. In this case we require a translation of 381 m in the X direction and 762 m in the Y direction. Note that in the IX_PARAGEO_Model_Name.ixf file a shift in the Z direction has already been applied (see IX Coupling Files).

 

IX_002_Fig07b

Schematic of ParaGeo mesh for the reservoir group before and after transformation required for mapping purposes

 

 

5The Surface_reference_level for IX is defined. In this case it is z=0.

6Output_ix_bin_file flag is set to 1 to output the required .bin mesh file.

 

 

END DATA is compulsory and defines the end of the simulation data and the start of the geometry definition data.

A summary of the data for defining the 3D geometry for this example is presented bellow. These data comprise nodal_data, geometry_line, Geometry_surface and Geometry_volume data structures.

 

Nodal_data

Data File

 

 

* Nodal_data NUM=1

! ----------------------------------

 Node_numbers  IDM=36

 1   2   3   4   5   6   7   8   9  10

 11  12  13  14  15  16  17  18  19  20

 21  22  23  24  25  26  27  28  29  30

 31  32  33  34  35  36                

 Coordinates  IDM=3  JDM=36

    0     0    -4591.812

    381   0    -4591.812

 

  (...)

 

  1143  1143 0

 

 

1All the nodes that will be used to define geometry lines are defined here.

2First node numbers are defined and then their corresponding X, Y and Z coordinates.

 

 

 

Lines

Data File

 

 

* geometry_line NUM=1

 line_type  1

 points  IDM=2

  1  2

 

* geometry_line NUM=2

 line_type  1

 points  IDM=2

  2  3

 

  (...)

 

* geometry_line NUM=        75        

 line_type 1                

 points IDM=2                

    27  36

 

175 lines are defined.

2Lines are type 1 (line connecting two nodes).

3The pair of nodes defining each line are specified.

 

 

 

Surfaces

Data File

 

 

* geometry_surface NUM=1                        

 surface_type 5                                

 lines IDM=4                                

    1  9  3  7

                         

* geometry_surface NUM=2                        

 surface_type 5                                

 lines IDM=4                                

    2  11  4  9

 

  (...)

 

* geometry_surface NUM=        52                        

 surface_type 5                                

 lines IDM=4                                

    36  72  48  75

 

 

152 surfaces are defined.

2Surfaces are type 5 (multi sided flat).

3Lines defining each surface are specified.

 

 

 

Volumes

Data File

 

 

* geometry_volume NUM=1                        

 Surfaces  IDM=6                                                

    1  5  17  19  35  37

                                         

* geometry_volume NUM=2                        

 Surfaces  IDM=6                                                

    2  6  18  20  37  39

 

  (...)

 

* geometry_volume NUM=12                        

 Surfaces  IDM=6                                                

    12  16  32  34  52  50

 

112 volumes are defined.

2The six surfaces defining each volume are defined.

 

 

 

 

Results

The result files for the project are in directory: IX_002\Generation\Results  

 

The following files which will be used in the simulation are generated:

•IX_002_geom.geo (ParaGeo geometry file)

•IX_002_gen_ix.bin (ParaGeo reservoir mesh in IX format)

 

IX_002_Fig03

ParaGeo geometry and mesh generated.

 

 

Considerations for generation of the .bin file only

The present case has covered an example in which both the ParaGeo .geo file and IX .bin file are generated. However there may be cases in which the .geo file is already available (as it has been previously generated) and the target is to generate the .bin file only. Here some considerations to take into account in such case are provided.

 

External ParaGeo Geometry

Data File

 

 

* Geometry_data

! ----------------------------                

 File_name       Example.geo

 File_format             hdf

 

1.The Geometry_data data structure is used to read the .geo file containing the ParaGeo geometry and mesh

2.For this case the datafile to generate the .bin file should not contain any other geometry data (nodal_data, Geometry_line, Geometry_surface or Geometry_volume) nor mesh data.

3.It should be noted that the .geo file may contain other data in addition to geometry and mesh. In some cases such additional data structures may contain other data structures assigned to it (e.g. a Time_curve may be assigned to Stratigraphy_surface_load data structure stored in the .geo file). Hence if the assigned time curve is not defined in the datafile the code will return an error. Thus two options can be undertaken in such cases:

a.Edit the .geo file to delete not required data structures that interfere with the .bin generation (e.g. using HDFView).

b.Define the time curves required (with the appropriate number) to run the datafile. In this case it is recommended to define a constant load factor of 0.0 to such time curve in order to make sure that there is no loading that could lead to small displacements during the generation of the .bin file.

4.As in the example described in this tutorial page, it is recommended to define only the minimal data required to generate the .bin file (e.g. Group_data, Geometry_set, Control_data, etc). As the target in to generate a .bin file only any loading data is irrelevant and is recommended to not be activated.

5.As in the example described in this tutorial page, it is recommended to define Support_data with fixities in X, Y and Z for all the domain volumes to ensure that there is no displacement occurring (event minimal) in the single time step run to generate the .bin file.

6.As the ParaGeo mesh is already in the .geo file, only one Control_data structure is required for generation of the .bin file which must be the last data structure in the data file.