The initial data file for the project is: Rest_001\Data\Rest_001_Case1.dat. The basic data includes:
1Geometry set data that define the formation tops and the pin line. 2Stratigraphy definition for the four formations present in the model.. 3Group data for the four formations which are assigned the "Elastic" properties using Group_control_data and Group_data data structures. 4A Material_data and Fluid_properties data structures defining the material properties for the formations. 5Support data (Support_data) defining fixity in X direction at the pin line location. 6Mesh control (Mesh_control) and Unstructured mesh generation data (Unstructured_mesh_data) defining a constant mesh size of 200m. 7Restoration_data defining the restoration operation and assigning a part geometry as a restoration surface. 8Part geometry data (Part_geometry_set, Part_line and Part_nodal_data) to define the restoration surface 9Time scaling data (Time_scaling_data) with optimal time step 5E-5 Ma. 10Damping data (Damping_global_data) to define bulk damping on the effective mean stress (Bulk Viscosity model) 11Control data (Control_data) for two stages defining: (a) Incremental solution algorithm (Type 1), (b) Maximum number of time steps of 108 (very large to avoid premature termination) (c) Duration of t=1 Ma, (d) Factor of critical time step = 0.5, (e) Plot file output every 0.2 Ma, (f) Plot file output at the end of the stage, (g) Screen message output every 1000 mech steps, (h) Output of a restart file at the end of the stage. 12Geometry data (nodal_data, Geometry_line and Geometry_surface) for definition of the 3D geometry.
The Geometry_set data for each of the boundaries is defined by:
1The name of the geometry set. 2A description for the geometry set. 3The geometry entities that constitute the geometry set.
Data File
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* Geometry_set NUM=1
Name "Formation4_top"
Description "Formation4_top"
Lines IDM=2
1 2
* Geometry_set NUM=2
Name "Formation3_top"
Description "Formation3_top"
Lines IDM=2
3 4
* Geometry_set NUM=3
Name "Formation2_top"
Description "Formation2_top"
Lines IDM=2
5 6
* Geometry_set NUM=4
Name "Formation1_top"
Description "Formation1_top"
Lines IDM=2
7 8
* Geometry_set NUM=5
Name "Formation1_base"
Description "Formation1_base"
Lines IDM=2
9 10
* Geometry_set NUM=6
Name "Pin_center"
Description "Pin_center"
Lines IDM=4
19 20 21 22
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1Six geometry sets are defined: a.Two for the top surface and base of the model b.Three for inter formation surfaces c.One for the pin location |
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The stratigraphy is defined by:
1Defining the existing stratigraphy layer depositional order and the group associated with each layer (via Stratigraphy_definition). 2Defining the topology of the top surface horizon for each stratigraphy layer (via Stratigraphy_horizon). The stratigraphy is defined in a similar way to Mech_002 where there is a fuller description provided.
Note that in geomechanical restoration simulations initialization the definition of the stratigraphy is compulsory.
Stratigraphy_definition
Data File
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* Stratigraphy_definition
Unit_Names IDM=4
"formation1"
"formation2"
"formation3"
"formation4"
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1Four formations present in the initial model. 2The group names coincide with their respective horizon names and unit names, so only the unit order is required.
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Stratigraphy_horizon
Data File
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* Stratigraphy_horizon NUM=1
Name "formation1"
Lines IDM=2
7 8
* Stratigraphy_horizon NUM=2
Name "formation2"
Lines IDM=2
5 6
* Stratigraphy_horizon NUM=3
Name "formation3"
Lines IDM=2
3 4
* Stratigraphy_horizon NUM=4
Name "formation4"
Lines IDM=2
1 2
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1The stratigraphy horizons for the four formations must be defined.
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Stratigraphy_smoothing
Data File
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* Stratigraphy_smoothing
Active_flag -1
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1Stratigraphy smoothing is deactivated
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The Group_data data structure is compulsory and defines the properties for each geometry group. For this example these comprise:
1The name of the group. 2The element type. 3The material assigned to the group 4The surfaces that define the geometry for the group. 5The type of porous flow
Data File
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* Group_data NUM=1
Group_name "formation1"
Element_type TPM3V
Material_name "Elastic"
Surfaces IDM=2
7 8
Porous_flow_type 5
* Group_data NUM=2
Group_name "formation2"
Element_type TPM3V
Material_name "Elastic"
Surfaces IDM=2
5 6
Porous_flow_type 5
* Group_data NUM=3
Group_name "formation3"
Element_type TPM3V
Material_name "Elastic"
Surfaces IDM=2
3 4
Porous_flow_type 5
* Group_data NUM=4
Group_name "formation4"
Element_type TPM3V
Material_name "Elastic"
Surfaces IDM=2
1 2
Porous_flow_type 5
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1Four groups are defined using the TPM3V (3 noded plane strain triangular elements using the average Volume formulation). 2The material assigned to these element groups is "Elastic". 3The geometry entities (surfaces) defining each group are assigned. 4The simulation will be performed using the porous flow type number 5 (hydrostatic drained assumptions with vertical effective stress calculated using the buoyant density). |
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The Group_control_data data structure is compulsory and defines:
1The groups number of geometry groups in the problem, where each geometry group 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
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* Group_control_data
Group_numbers IDM=4
1 2 3 4
Active_geomechanical_groups IDM=4
1 1 1 1
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Two groups are present in the simulation with the geomechanical active.
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The material properties for the material "Elastic" as well as its associated fluid properties are defined in the datafile.
Data File
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* Material_data NUM=1
Material_name "Elastic"
Units IDM=4
"MPa"
"m"
"Ma"
"Celsius"
Isotropic_elastic_properties IDM=2
50000
0.20
Grain_density 2760
Grain_stiffness 30000
Porosity 0.50
Singlephase_fluid 1
* Fluid_properties NUM=1
Fluid_type "Water"
Density 1000
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1A single material is used for the simulation. 2The material is named "Shale_CF75". 3Elastic properties (Young's modulus and Poisson's ratio) are defined for the material. 4Grain properties (density and stiffness) are defined. 5An arbitrary initial porosity of 0.5 is defined. 6Fluid properties number 1 are assigned to material "Elastic". 7Definition of a fluid with its fluid density is compulsory for groups with porous_flow_type = 5
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The support data is used to define the fixity in X direction at pin location.
Data File
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* Support_data
Displacement_codes IDM=2 JDM=3
1 0
0 1
1 1
Displacement_code_geom_set IDM=1
"Pin_center"
Displacement_code_geom_ass IDM=1
1
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1Three displacement code sets are defined. 2Displacement code set number 1 (fixity in X direction) is assigned to the geometry set with the lines that defines the axial plane of the fold ("Pin_center").
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An "unstructured mesh" with 200m size plane strain triangular elements is defined for this example.
Data File
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* Mesh_control_data
Generation_algorithm 2
Mesh_generation_flag 0
* Unstructured_mesh_data
Default_element_size 200
Element_size_bounds IDM=2
200
/ 200
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1The algorithm used for this simulation is set to 2 (i.e. unstructured mesh). 2The mesh generation flag is set to 0 so analysis will be performed after mesh generation (default). 3The element size is set to 200 m.
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Restoration data and restoration surface data are defined.
Data File
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* Restoration_data
Restoration_surface "Restoration_surface"
Operation_type "Translate"
* Part_geometry_set NUM=1
Name "Restoration_surface"
Part_lines IDM=1
1
* Part_line NUM=1
Facets IDM=2 JDM=1
1 2
* Part_nodal_data NUM=1
Nodes IDM=2
1 2
Coordinates IDM=2 JDM=2
-5000.0 5000
19000.0 5000
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1A Restoration_data structure is defined (compulsory for geomechanical restoration simulations). 2The part geometry named "Restoration_surface" is assigned as a restoration surface. 3The restoration operation for the first control stage is set to "Translate" (the model top surface is unfolded and translated to coincide with the restoration surface). 4Part geometry data is used to define the restoration surface which is a straight horizontal line at Y=5000m.
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Bulk viscosity damping is defined in order to damp the compression part of the dynamics-related oscillations on the effective mean stress.
Data File
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* Damping_global_data
Percentage_damping 0.02000
Bulk_damping_model "BulkViscosity"
Bulk_damping_properties IDM=1
0.50000
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A bulk viscosity model with a bulk viscosity constant of 0.5 is used in this example in order to damp the compressive oscillations due to dynamics in the effective mean stress. This is a generally recommended set up for most of ParaGeo geomechanical analysis. (For more information on the bulk viscosity model see damping_global_data).
Note that despite percentage damping being also defined, this will not be active as percentage damping and bulk damping are mutually exclusive and the latter takes precedence.
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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
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* Time_scaling_factors
Optimal_time_step 0.5E-04
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An optimal time step of 5.0·10-5 Ma is defined.
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The current analysis considers two control stages with identical data defined by the Control_data structure in which control data for the geomechanical fields is provided. For more information see Solution Control Data.
Data File
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* Control_data
Control_title "Translate"
Solution_algorithm 1
Maximum_number_time_steps 1E8
Duration 1.0
Factor_critical_time_step 0.5
Output_time_plotfile 0.2
Output_frequency_plotfile -1
Screen_message_frequency 1000
Output_frequency_restart -1
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1Duration for control stage is set to 1.0 Ma is defined. 2The solution algorithm is set to number 1, i.e. Transient dynamic algorithm. 3The maximum number of time steps is set to 108. 4The 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. 5Information will be displayed on the screen (command prompt) every 1000 mech steps. 6A plot file is requested every 0.2 Ma (Output_time_plotfile=0.2) and at the end of the stage (Output_frequency_plotfile=-1). 7Output of a restart file is requested at the end of the control stage. |
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Restoration_data is overwritten for the second control stage.
Data File
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* Restoration_data
Restoration_surface "Restoration_surface"
Operation_type "Restore"
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1Restoration data is overwritten to change the operation to "Restore" (current top formation is deactivated/eliminated and the new top surface is translated to coincide with the restoration surface). 2Usually in restoration simulations the first control stage will be set to "Translate" and all the subsequent ones to "Restore" for which re-specification of the restoration data is only required after the first control stage |
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A summary of the data for defining the 2D geometry for this example is presented below. These data comprise nodal_data, Geometry_surface and Geometry_line data structures.
Nodal_data
Data File
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* nodal_data
node_number IDM=104
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
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.
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101 102 103 104
coordinates IDM=2 JDM=104
14000 2624.4
12916.7 3188.3
11788.3 3655.7
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1400 199.5
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1All the nodes that will be used to define geometry lines are defined here. 2Note that some nodes have repeated coordinates and will not be used for the present example.
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Surfaces
Data File
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* geometry_surface NUM=1
surface_type 5
lines IDM=4
1 19 3 11
* geometry_surface NUM=2
surface_type 5
lines IDM=4
2 12 4 19
.
.
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* geometry_surface NUM=8
surface_type 5
lines IDM=4
8 18 10 22
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1Eight surfaces are defined (two per each formation). 2Each surface is defined by four lines.
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Lines
Data File
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* geometry_line NUM=1
line_type 4
points IDM=7
1 2 3 4 5 6 7
* geometry_line NUM=2
line_type 4
points IDM=7
7 8 9 10 11 12 13
.
.
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* geometry_line NUM=22
line_type 1
points IDM=2
72 98
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1Twenty two lines are defined (not all of them will be used). 2Some lines are type 1 (line connecting two nodes) whereas some lines are type 4 (poly-lines).
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