Case03a 3D Small Irregular Grid Model with 'Ragged' Boundaries

 

The 3D small irregular grid model with 'ragged' boundaries presented here is extracted from the basin model at the highlighted location in pink outline. A full description of the geomechanical restoration and forward simulation for this 3D small irregular grid model will not be described.  This model is similar to the Case02 slice model with directional strain decompaction, therefore only description of additional data or data different to the slice model is presented here.  To this end, it is recommended to familiarise with the Case02 - Slice Model before undertaking this example.

 

Simulation runs on a single 3.6GHz AMD Processor PC for Case03a small 3D irregular grid model comprising 47,207 nodes, 43,279 elements took:

•Restoration - 39 minutes.

•Forward Simulation - 1 hours 31 minutes.

 

 

Geol_002_03a_01

3D Small Irregular Grid Model located at Grid cells i=34-80, j=1-15 in Geol_002 Basin Model with 80 x 80 grid cells (1 cell = 1km)

 

 

The workflow compared to the slice model comprise an additional Step 04a as:

1Step 01 - Zmap file import and output to ParaView plot file and Abaqus input .inp file.

2Step 02 - Conversion of .inp file to suitable ParaGeo geometry (.geo and .geometry) files and data .dat file.

3Step 03 - Geomechanical restoration of the defined 3D geological structure with directional strain decompaction.

4Step 04a - Extraction of side boundary nodes for 'ragged' boundary models.  Note that this is valid for hex mesh only and performed for models with 'ragged' boundaries.  It is to be carried out prior to performing Step 04.

5Step 04 - Forward simulation of the sedimentation process (THM modelling).

 

Each of these steps contains only a description of additional data or data different to the slice example in their respective sections following.

 

Click to expand/collapseStep 01 - Zmap file import and output to ParaView plot file and Abaqus input file

 

The Zmap import data files for the slice model are in : Geol_002\Case03a\01 - Zmap import\Data. The key differences in the Step 01 workflow is in the main Zmap import data file Geol_002_Case03a_geom.dat.

 

Geol_002_01_01

Workflow Flowchart for Step 01 - Zmap Import

 

Data File Description

 

The main data file (Geol_002_Case03a_geom.dat) for importing and processing Zmap data with the mesh discretization shown below is described with key differences to the Case02 slice model.

 

Geol_002_03a_02

Extraction of Small Irregular Grid (Sub-) Model from 'Actnum' Geol_002 Basin Model and Discretisation of Grids in i, j, k

 

 

Data File

 

 

* Util_eclipse_import

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

  ........

 

 Output_file_name        "Geol_002_Case03a_abaq"

 

  ........

 

 Sub_grid_dimensions  IDM=6

  /I,J,K Minimum/  34 1  1

  /I,J,K Maximum/  80  15  10

 

  ........

 

 Grid_subdivision_i   2

 Grid_subdivision_j   2

 Grid_subdivision_list_k IDM=10   JDM=2

  /Layer Number/       1  2  3  4  5  6  7  8  9  10

  /No. Subdivisions/   3  3  3  3  3  3  5  3  3 1

 

  ........

 

1Util_eclipse_import data different to the Case02 slice model are in bold text.  These include:

a.Output_file_name - Defines output file name to be "Geol_002_Case03a_abaq".

b.Sub_grid_dimensions - Defines the minimum and maximum extent of the subgrid in i, j and k directions to extract and output.

c.Grid_subdivision_i (_j and _k) - Defines the grid sub-divisions in i, j and k directions.  Note that in the Eclipse coordinate system, k direction is top to bottom, so layer 1 corresponds to the topmost layer, i.e. formation10.

 

 

 

 

 

Results

 

The results of the Zmap import for the irregular grid model are in : Geol_002\Case03a\01 - Zmap import\Results. The key results file include:

 

•Geol_002_Case03a_abaq.inp - Abaqus input file of extracted irregular grid model which can be readily converted to ParaGeo data in Step 02.

•Geol_002_Case03a_geom_update_eclipse.xmf (and .ecl) - ParaView plot files of extracted irregular grid model (see figure below).

 

Geol_002_03a_03

Extracted Irregular Grid Model from Zmap Import (Geol_002_Case03a_geom_update_eclipse.xmf, .ecl)

 

 

Click to expand/collapseStep 02 - ParaGeo Geometry Creation

 

The data files for the ParaGeo geometry creation for the irregular grid model are in : Geol_002\Case03a\02 - Geometry creation\Data. The only difference compared with the slice model in the Step 02 workflow is the Case## ID name in the main ParaGeo geometry creation file Geol_002_Case03a_rest.inp.

 

Geol_002_01_08

Workflow Flowchart for Step 02 - ParaGeo Geometry Creation

Results

 

The results of the geometry creation data for the irregular grid model are in : Geol_002\Case03a\02 - Geometry creation\Results. The key results file include:

 

•Geol_002_Case03a_rest.dat - ParaGeo data file for use in geomechanical restoration Step 03.  Note that this generated data contains minimum data and the final data used in restoration will be mostly edited.

•Geol_002_Case03a_rest.geo - ParaGeo "hdf" format geometry file to be included in Step 03.

•Geol_002_Case03a_rest.geometry - ParaGeo geometry file with geometry, group and stratigraphy data to be included in Step 03.

 

The figure for the ParaGeo irregular grid model hex mesh (Geol_002_Case03a_rest_mesh.xmf) created from the Abaqus input file is the same as that shown in Step 01 for the extracted Zmap grid output file (Geol_002_Case03a_geom_update_eclipse.xmf, .ecl).

 

 

Click to expand/collapseStep 03 - Restoration

 

Step 03 involves performing the geomechanical restoration for the irregular grid model with directional strain decompaction (similar to the slice model) as shown in the flowchart below.  The restoration data files for the irregular grid model are in: Geol_002\Case03a\03 - Restoration\Data.

 

Geol_002_02_05

Workflow Flowchart for Step 03 - Restoration

 

Geol_002_03a_04

Initial Irregular Grid Model showing prescribed boundary conditions

 

 

Geol_002_03a_05

Initial Irregular Grid Model showing locations of notional 'Well_01' and 'Well_03'

 

Basic Set Up: Data File Description

 

Key differences in the restoration data compared against the slice model comprise:

1Geol_002_Case03a_RestSurf01.dat: Part geometry data for horizontal restoration surface named "Restoration_surface" located at Z=8700m, just above the topmost Z-coordinate of the irregular grid model, and extending slightly beyond the lateral boundaries.

2Geol_002_Case03a_Directional_Strains.spat: File containing the directional strain spatial grid data with 3% strain in XX for the entire small irregular grid model domain.

3Main restoration data file Geol_002_Case03a_rest.dat.

 

These differences are described in the respective sections following.

 

The restoration surface data file Geol_002_Case03a_RestSurf01.dat comprise part geometry data for the restoration surface sited just above the topmost Z-coordinate of the model and extending slightly beyond the lateral boundaries.

 

Data File (Geol_002_Case03a_RestSurf01.dat)

 

 

 (........)

 

* Part_nodal_data  NUM=1

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

 Nodes   IDM=4

   1  2  3  4

 Coordinates  IDM=3  JDM=4

   30000 -5000  8700

  83000 -5000  8700

        83000 20000  8700        

   30000 20000  8700

 

1Part geometry coordinate data defined to cover the whole lateral profile of the irregular grid model and located at Z=8700m, just above the topmost Z-coord of the initial model.

 

Geol_002_03a_06

 

 

 

Geol_002_Case03a_Directional_Strains.spat file containing the directional strain spatial grid data with 3% strain in XX for the entire small irregular grid model domain.

 

Data File (Geol_002_Case03a_Directional_Strains.spat)

 

 

* Spatial_grid  NUM=1

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

 

   (........)

 

 Grid_coordinates   IDM=3  JDM=8

   30000.0 -5000.0  0.0

        83000.0 -5000.0  0.0

   30000.0  20000.0  0.0

  83000.0  20000.0  0.0

   30000.0 -5000.0  10000.0

  83000.0 -5000.0  10000.0

   30000.0  20000.0  10000.0

  83000.0  20000.0  10000.0

 

   (........)

 

1Directional strain spatial grid data with 3% strain in XX defined with a single grid unit comprising eight grid coordinate data with values large enough to encompass the model domain boundaries in X, Y and Z directions.

 

 

 

 

 

Key differences (from the slice model) in the main restoration data file Geol_002_Case03a_rest.dat comprise:

1Update all references of Case## ID.

2Support data to fix the "South" boundary in Y and "East" boundary in X. Other boundaries are left "free"/unconstrained.

3History section line data for notional 'Well_03' replaces notional 'Well_02' to output porosity at this well location for the initial model (Optional).

 

Following are descriptions of the key restoration data differences:

 

 

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 0

 Displacement_code_geom_set IDM=2

  "East"

   "South"

 Displacement_code_geom_ass IDM=2

    1  2

1Support_data defining "East" boundary fixed in X and "South" fixed in Y.

 

Note that no other constraint data (e.g. Couple_freedoms) is required.

 

 

 

 

 

 

 

 

 

Notional 'Well_03' history section line data at the location shown in the figure above replaces 'Well_02'.  History section line data for 'Well_01' is as defined for the slice model.

 

Data File

 

 

* History_section_line      NUM=2

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

 Name           "Well_03_las"

 

   (........)

 

 Plan_coordinates  IDM=2

  70000 8000

 

   (........)

 

1History_section_line data for notional 'Well_03' is defined to output (in .las format) the initial porosities of the formation layers along a vertical well path defined by the coordinates specified.

 

 

 

The results of the geomechanical restoration for the irregular grid model are in : Geol_002\Case03a\03 - Restoration\Results. The key results files from the restoration step to be used in Step 04 forward simulation include:

 

•Geol_002_Case03a_rest_formation01.geo - Geometry file for the pre-existing layer in the forward simulation in Step 04.  This file is also used in Step 04a to extract all the side boundary nodes which includes the 'ragged' side boundaries.

•Geol_002_Case03a_rest_Disp_formation##.spat - Spatial boundary displacement data from restoration to be applied to the forward simulation in Step 04.

 

The evolution of porosity plots for the initial configuration, translation + directional strain decompaction and various restoration stages are shown below.

 

 

Geol_002_03a_08

 

Evolution of porosity results at initial configuration, translation + directional strain decompaction and various restoration stages to end of restoration at t=11 Ma

 

 

Click to expand/collapseStep 04a - Boundary Extract

 

Step 04a involves the extraction of side boundary nodes to be carried out prior to performing forward simulation in Step 04 for 'ragged' boundary models. Note that this workflow is valid for hex mesh only and performed for models with 'ragged' boundaries.

 

The boundary extract data files for the irregular grid model are in: Geol_002\Case03a\04a - Boundary Extract\Data. The flowchart below summarises the data input and results output file involved in the boundary extract process.  The geometry file to be used from Step 03 is in blue text and the results output file to be used in Step 04 is in brown text.

 

Geol_002_03a_14

Workflow Flowchart for Step 04a - Boundary Extract

 

 

 

Data File (Geol_002_Case03a_extract_hex_sidebound.dat)

 

 

* Geometry_data

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

 File_name   "Geol_002_Case03a_rest_formation01.geo"

 File_format                 hdf

 

 

* Units

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

 Length                   "m"

 Stress                   "MPa"

 Time                     "Ma"

 Temperature              "Celsius"

 

 

* Stratigraphy_definition

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

 Unit_Names    IDM=1

  "formation01"

 Basal_horizon   "Basal_surface"

 

 

* Stratigraphy_horizon      NUM=1

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

 Name             "formation01"

 Geometry_set   "formation01_1"

 

 

* Stratigraphy_smoothing

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

 Active_flag      -1            

 

 

* Util_create_hex_boundary

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

File_name  "Geol_002_Case03a_FwdSim_01_sidebound"

 

1Geometry_data to read in 'hdh' file format geometry file for pre-existing layer, i.e. formation01, in this case.

 

 

 

 

 

 

 

 

 

2Stratigraphy_definition data to define the pre-existing unit name and basal horizon name. This information is obtained from the .geometry file from Step 02 results.

 

3Stratigraphy_horizon data to define the geometry set name for the horizon for stratigraphy unit "formation01". This information is obtained from the .geometry file from Step 02 results.

 

4Stratigraphy_smoothing with Active_flag set to -1 ensures any stratigraphy smoothing is deactivated.

 

5Util_create_hex_boundary data is a utility that extracts hex mesh boundary nodes from the geometry file defined in Geometry_data and outputs into the user defined file named "Geol_002_Case03a_FwdSim_01_sidebound". This file contains a Geometry_set named "sides" which contains all the side boundary nodes of the 'ragged' boundary but excluding any nodes on the base.

 

 

 

The results of the boundary extract workflow for the irregular grid model are in : Geol_002\Case03a\04a - Boundary Extract\Results. The key results file to be used in the forward simulation in Step 04 include:

 

•Geol_002_Case03a_FwdSim_01_sidebound.dat - This file contains a Geometry_set named "sides" which contains all the side boundary nodes including the 'ragged' boundaries on the irregular grid model but excluding any nodes on the base.  "Sides" will be used in the forward simulation to apply the spatial boundary data from restoration.

 

 

 

Click to expand/collapseStep 04 - Forward Simulation

 

Step 04 involves performing the forward simulation for the irregular grid model as shown in the flowchart below. An additional file from the Step 04a, shown in brown text, is required for data input.  The other key files involved are the same as for the Case 02 slice model, likewise the simulation stages and processes involved are the same but with minor changes which are described in the next section.

 

The forward simulation data files for the irregular grid model are in: Geol_002\Case03a\04 - Forward simulation\Data.

 

Geol_002_03a_15

Workflow Flowchart for Step 04 - Forward Simulation

 

Basic Set Up: Data File Description

 

Key differences in the main forward simulation data from the slice model comprise:

1Update all references of Case## ID.

2Include file Geol_002_Case02_FwdSim_01_sidebound.dat containing Geometry_set "Sides" used to define the spatial boundary data for the side boundaries from restoration.

3Support_data for the geometry sets "Sides" replacing the "North", "South", "East" and "West" constraint data.

4Single Spatial_boundary data defining the displacements for "Sides" from restoration replacing the four spatial boundary data for "North", "South", "East" and "West".

5Two history section line data for notional 'Well_03' replaces notional 'Well_02' to output selected variables in "las" and "hdh" formats (optional).

 

These differences are described in the respective sections following.

 

Data File

 

 

* Include

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

 Filename   "Geol_002_Case03a_FwdSim_01_sidebound.dat"

 

1File containing Geometry_set "Sides" created in Step 04a.

 

 

 

 

Data File

 

 

* Support_data          NUM=1

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

 Displacement_codes IDM=3 JDM=5

 /Set 1/     1 0 0

 /Set 2/     0 1 0

 /Set 3/     0 0 1

 /Set 4/     1 1 0

 /Set 5/     1 1 1

 Displacement_code_geom_set IDM=2

  "Sides"

  "Basal_surface"

 Displacement_code_geom_ass IDM=2

  4  5

 

1Geometry set "Sides" is constrained laterally in X and Y.

 

 

 

Data File

 

 

* Spatial_boundary           NUM=2

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

 Name                                 "Sides"

 File_name           "Geol_002_Case03a_rest_Disp_formation01.spat"

 Boundary_type      "Spatial_grid"

 Time_curve         "Step_scurve"

 Conforming_mesh_flag      0

 Spatial_grids  IDM=1

   "Disp"

 Geometry_sets  IDM=1

  "Sides"

 Prescribed_components IDM=2 JDM=1

    1  2

 

1For irregular grid model with 'ragged' boundaries, this single "Sides" spatial boundary data replaces the four individual spatial boundary data for "North", "South", "East" and "West".

 

 

 

Two history section line data for notional "Well_03" replaces "Well_02" to output selected variables in "las" and "hdh" formats.

 

Data File

 

 

* History_section_line      NUM=3

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

 Name               "Well_03_las"

 

  (......)

 

 Plan_coordinates  IDM=2

  70000 8000

 

  (......)

 

 

 

* History_section_line      NUM=4

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

 Name               "Well_03_hdh"

 

  (......)

 

 Plan_coordinates  IDM=2

  70000 8000

 

  (......)

 

1History_section_line data set 3 in "las" format and data set 4 in "hdh" format are defined for the notional 'Well_03', replacing 'Well_02', at the new location coordinates.

 

 

 

 

 

 

The results of the forward simulation for the irregular grid model are in : Geol_002\Case03a\04 - Forward simulation\Results. Results of the high definition history files for the output variables in "Well_03" have been processed into the excel file 00_Geol_002_Case03a_Results.xlsx. Some of the graphical plots are presented at the end of the results section.

 

A comparison of the target configuration and the predicted forward model configuration show very good correlation achieved in all bar the top layer (i.e last deposition layer).  This is expected due to the inconsistency in the initialization of the top layer to the NCT during forward simulation whereas in the restoration, decompaction to "Top_layer" following the NCT starts in the second restoration stage. "Continuous" decompaction can only be defined for the first restoration stage (after geostatic initialization) due to directional strain decompaction happening at the same time.

 

Geol_002_03a_07

Comparison of target configuration and predicted forward model configuration (nb: plots are of material number)

 

 

The figure below shows the evolution of porosity plots in the generated forward model from initial configuration to end of deposition stage.  A comparison evolution plot of the restoration process is also presented.

 

 

Geol_002_03a_09

 

Evolution of porosity in the generated forward model from initial configuration, various stages of deposition to end of forward simulation at t=120 Ma

 

 

 

Geol_002_03a_08

 

Evolution of porosity in the restoration model from initial configuration, translation and various restoration stages to end of restoration at t=11 Ma

 

 

The figures below show the distribution of temperature, kinetic KTR, kinetic Vitrinite reflectance, porosity, displacements in Z, strain in ZZ, stress in ZZ, pore pressure, over-pressure and permeability in Z.  The basal thermal flux loading has resulted in increase in temperature up to 166°C at the base and c.a. 141°C in the kerogen formation02 layer, which is sufficient to produce a kinetic KTR percentage of 79% transformation.  Over the simulation duration of 120Ma, over-pressures up to 52MPa have developed predominantly in the bottom two shale layers with under-pressures up to 6MPa focused on the East end of the model in the three adjacent layers (sandstone layers 03 and 07 and 80% sandstone layer 04 sandwiched in between). Permeability in Z is observed to be highest in sandstone layer 07.

 

Geol_002_03a_10

 

Geol_002_03a_11

Geol_002_03a_12

 

Distribution of variables in generated forward model. Variables include Temperature, Kinetic KTR, Kinetic Vitrinite Reflectance, Porosity, Displacement in Z, Strain in ZZ, Stress in ZZ, Pore Pressure, Over-Pressure and Permeability in Z

 

 

The graphs below show plots of porosity, pore pressures and stresses along the notional 'Well_03' line.  The comparison plots of porosity between the target and the generated forward model show greater deviation in the bottom two shale layers.  As observed in the pore pressure plot, this is due to over-pressures generated which are highest in these two layers. The vertical and horizontal effective stresses have reduced at these lower levels to compensate for the increase in pore pressure.  The locations of the layers are highlighted with the dotted lines at their respective depths.

 

 

Geol_002_03a_16

 

Porosity, Pore Pressure and Stresses at end of forward simulation stage

 

 

The graphs below show plots of kinetic KTR and temperature along the notional 'Well_03' line. As expected, the kerogen formation02 layer shows hydrocarbon expulsion with kinetic KTR of c.a. 11 - 16.5% at temperatures of c.a. 92 - 101°C.

 

Geol_002_03a_17

 

Kinetic KTR and Temperature distribution at end of forward simulation stage