The initial data file for the project is: Rest_002\Data\Rest_002_Step1.dat. The basic data includes:
1Geometry_set data that define the west boundary and the fault hanging wall and footwall. 2Mesh control (Mesh_control) and Unstructured mesh generation data (Unstructured_mesh_data) defining a constant mesh size of 125m. 3Group data for the three 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. 5Contact data for the fault (Contact_set, Contact_property and Contact_global). 6 Fault_set data to identify the fault. 7Stratigraphy_definition for the three formations present in the model and corresponding Stratigraphy_horizon data. 8Geostatic_data to initialize the model to a porosity trend via Spatial_variation_definition and Spatial_variation_values data structures. 9Support data (Support_data) defining fixity in X direction at the west boundary. 10Part geometry data (Part_geometry_set, Part_line and Part_nodal_data) to define the restoration surface. 11Restoration_data defining the restoration operation, restoration top surface boundary conditions and assigning a part geometry as a restoration surface. 12Control data (Control_data) for four stages defining: (a) Incremental solution algorithm (Type 1), (b) Target number of time steps of 10000, (c) Maximum number of time steps of 10000, (d) Duration of t=1 Ma, (e) Plot file output every 0.2 Ma, (f) Plot file output at the end of the stage, (g) Screen message output every 500 mech steps, (h) Output of a restart file at the end of the stage. 13Geometry data (nodal_data, Geometry_line and Geometry_surface) for definition of the 2D geometry.
Note that the initial stage is defined with less steps as the objective is only to initialise the model with the target porosity vs depth trend.
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 "fault1_ftw"
Lines IDM=3
2 5 8
* Geometry_set NUM=2
Name "fault1_hgw"
Lines IDM=3
14 17 20
* Geometry_set NUM=3
Name "West"
Lines IDM=3
4 7 10
* Geometry_set NUM=4
Name "East"
Lines IDM=3
12 15 18
* Geometry_set NUM=5
Name "Basal_horizon"
Lines IDM=2
1 11
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1Five geometry sets are defined: a.Two for the fault hanging wall and fault footwall b.Three for model sides and basal boundaries |
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An "unstructured mesh" with 125m 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 125
Element_size_bounds IDM=2
125
/ 125
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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 125 m.
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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=3
1 2 3
Active_geomechanical_groups IDM=3
1 1 1
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Three groups are present in the simulation with the geomechanical active.
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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
1 4
Porous_flow_type 5
* Group_data NUM=2
Group_name "formation2"
Element_type "TPM3V"
Material_name "Elastic"
Surfaces IDM=2
2 5
Porous_flow_type 5
* Group_data NUM=3
Group_name "formation3"
Element_type "TPM3V"
Material_name "Elastic"
Surfaces IDM=2
3 6
Porous_flow_type 5
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1Three 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 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"
Elastic_properties IDM=2
50000
0.20
Grain_density 2760
Grain_stiffness 30000
Porosity 0.50
Singlephase_fluid 1
Decompaction_Type 1
Decompaction_spatial 1
Decompaction_properties IDM=1
0.001
* 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 "Elastic". 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". 7Decompaction_type is set to 1 in order to decompact to a prescribed porosity trend. 8Spatial_variation_values number 1 is assigned as the porosity trend to calculate decompaction (Decompaction_spatial = 1). 9The maximum porosity increment between consecutive time steps is set to 0.001. 10Definition of a fluid with its fluid density is compulsory for groups with porous_flow_type = 5.
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Contact data to define a frictionless contact surface for the fault.
Contact_set
Data File
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* Contact_set NUM=1
Name "All"
Algorithm "Penalty"
Property_name "Block_friction"
Global_update_frequency 1000
Field_factor 0.2
Buffer_factor 5.0
All_geometry_flag 1
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1A single contact set is defined 2Penalty algorithm is selected (currently only option available) 3"Block_friction" property is assigned to the contact set 4Global contact search frequency is set to every 1000 mech steps 5Field factor is set to 0.2 so the maximum normal gap is defined as Gn = 0.2· lfacet where Gn is the normal gap and lfacet is the contact facet length. 6The buffer factor for defining the buffer box size is set to 5.0 (the candidate target facets that can potentially establish a contact relationship with a given contactor node are those within the buffer box during a global search update). In this case the buffer box for a given node is an sphere centred at the node with radius R=5.0· lfacet where lfacet is the average length of the facets that terminate on the node. 7Global geometry flag for usage of all external surfaces is set to ON.
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Contact_property
Data File
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* Contact_property NUM=1
Name "Block_friction"
Compression_model 1
Compression_properties IDM=1
2000
Adhesion_model 1
Adhesion_properties IDM=1
2000
Tangential_model 2
Tangential_properties IDM=2
100
0.0
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1A contact property named Block_friction is defined. 2Linear elastic compression model is assigned (compression model 1) with a normal penalty stiffness of 2000 MPa. 3Linear adhesion model is assigned (adhesion model 1) with a normal penalty stiffness of 2000 MPa. 4Coulomb friction model is assigned for tangential contact (tangential model 2) with a tangential penalty stiffness of 100 MPa and a friction coefficient of 0.0.
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Contact_global
Data File
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* Contact_global NUM=1
Included_contact_sets IDM=1
"All"
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1Contact_global data structure is defined to specify that defined contact set named "All" is active.
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The Fault_set data is used to identify geometry entities which form part of individual faults. This can be used to track fault geometries during restoration and insert faults later during the restoration-derived forward simulation.
Data File
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* Fault_set NUM=1
Name "Fault1"
Hangingwall_set "fault1_hgw"
Footwall_set "fault1_ftw"
Contact_sets IDM=1
"All"
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1A fault set is defined for the normal fault. 2Name "Fault1" is defined for the fault set. 3Geometry sets defining fault hanging wall and fault footwall are assigned. 4Contact_set named "All" is assigned to the fault set |
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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=3
"formation1"
"formation2"
"formation3"
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1Three 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
3 13
* Stratigraphy_horizon NUM=2
Name "formation2"
Lines IDM=2
6 16
* Stratigraphy_horizon NUM=3
Name "formation3"
Lines IDM=2
9 19
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1The stratigraphy horizons for the three formations must be defined.
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Geostatic data is used to initialize the model with an specified porosity distribution via Spatial_variation_values. That porosity distribution will be used also to calculate decompaction.
Data File
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* Geostatic_data NUM=1
Groups IDM=3
"formation1"
"formation2"
"formation3"
Porosity_spatial 1
* Spatial_variation_definition NUM=1
Description "Porosity vs. Depth"
Type "Absolute"
Distribution "Depth_dependent"
Variation_assignment 1
* Spatial_variation_values NUM=1
Description "Normal Compaction Trend"
Time 0.0
Values_vs_depth IDM=35 JDM=2
0 179.3 ... 6097.4
0.48834 0.44717 ... 0.039523
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1Geostatic initialization is applied to the 3 formations present in the model. 2Porosity is initialized with the data defined in the Spatial_variation_definition number 1. 3The Spatial_variation_definition is assigned the porosity trend in depth defined in the Spatial_variation_values number 1. |
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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=3 JDM=3
1 0 0
0 1 0
1 1 0
Displacement_code_geom_set IDM=1
"West"
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 West boundary.
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Restoration data and restoration surface data are defined.
Data File
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* 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
-100.0 1700
6100.0 1700
* Restoration_data
Restoration_surface "Restoration_surface"
Operation_type "Translate"
Decompaction_Type "Top_layer"
Move_to_surface_type "Bed_length"
Pin_coordinates IDM=1
0.0
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1Part_geometry_set, Part_line and Part_nodal_data structures are used to define a flat restoration surface with 1700 m of elevation 2A Restoration_data structure is defined (compulsory for geomechanical restoration simulations). 3The part geometry named "Restoration_surface" is assigned as a restoration surface. 4Move_to_surface_type is set to "Bed_length" to assume displacement-based bed length preservation on the top surface. 5The pin coordinates are at X=0 (same as pinned West boundary) 6The Decompaction_type is set to "None" in the geostatic stage and "Top_layer" in the subsequent stages. The latter maximises the consistency between the restoration and forward simulation formation thicknesses. 7The restoration Operation_type for each of the stages is defined as follows: i.Stage 1: "None" (geostatic assignment of initial porosity) ii.Stage 2: "Translate" (the model top surface is unfolded and translated to coincide with the restoration surface). iii.Stage 3 and Stage 4: "Restore" (the top formation is removed and the new top surface is translated to the restoration surface).
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The current analysis considers four control stages 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 formation1"
Solution_algorithm 1
Target_number_time_steps 10000
Maximum_number_time_steps 1E6
Termination_time 2.0
Screen_message_frequency 500
Output_time_plotfile 0.2
Output_frequency_plotfile -1
Output_frequency_restart -1
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1Duration for each control stage is 1.0 Ma. 2The solution algorithm is set to number 1, i.e. Transient dynamic algorithm. 3The target number of time steps is set to 10000 for the control stage. 4The maximum number of time steps is set to 1E6. 5The first control stage is set to terminate at time = 1 Ma. 6Information will be displayed on the screen (command prompt) every 500 mech steps. 7A plot file is requested every 0.2 Ma (Output_time_plotfile=0.2) and at the end of the stage (Output_frequency_plotfile=-1). 8Output of a restart file is requested at the end of the control stage.
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A summary of the data for defining the 2D geometry for this example is presented bellow. 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=16
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16
coordinates IDM=3 JDM=16
0 0 0
3366.05 0 0
.
.
.
2500 1500 0
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1All the nodes that will be used to define geometry lines are defined here.
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Surfaces
Data File
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* geometry_surface NUM=1
surface_type 1
lines IDM=4
1 2 3 4
* geometry_surface NUM=2
surface_type 1
lines IDM=4
3 6 5 7
.
.
.
* geometry_surface NUM=6
surface_type 1
lines IDM=4
16 18 19 20
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1Six surfaces are defined (two per each formation). 2Each surface is defined by four lines. 3Surfaces are type 1 (linear parametric).
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Lines
Data File
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* geometry_line NUM=1
line_type 1
points IDM=2
1 2
* geometry_line NUM=2
line_type 1
points IDM=2
2 3
.
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* geometry_line NUM=20
line_type 1
points IDM=2
16 14
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1Twenty lines are defined. 2Lines are type 1 (line connecting two nodes).
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