user guide of numerical simulation gridding v2.2.0

User guide of numerical simulation

gridding module

1 Quick look

1.1 Introduction

This module provide Upscaling and export three types of grid. On the basis of reservoir

geological model or structural model, numerical simulation gridding module is used for

creating grid which is more appropriate for simulation. While this necessitates the omission of

much of the geological models fine detail in this process, the result is intended to preserve

representative simulation behavior.

This module provides three types of grid: stair-step grid, truncated rectangular grid and PEBI

grid (Fig. 1-1).

Stair-step grid

This grid has excellent advantage in dealing with complicated fault geometry, so it can

represent faults and support transmissibility adjustments without skewing and distorting the

grid in the vicinity.

Truncated rectangular grid

Accurately describe any complex model.

PEBI grid

With the advanced triangular mesh generation technique, the system can directly generate

PEBI grid which breakthroughs the limitation of the traditional grid and is able to divide

any shape of reservoir area. PEBI grid has a high degree of flexibility in looking for

remaining oil distribution and simulating any complicated faults or boundary. It also can

accurately simulate coning problem of vertical and horizontal wells, which is helpful to

reduce the influence of grid strike on simulation results.

Fig. 1-1 Grid types

1.2 Module relationships

As mentioned before, the numerical simulation gridding module based on reservoir geological

model and structural model, the relationships between the structural modeling module and

reservoir geological model are illustrated in Fig. 1-2.

Fig. 1-2 Module relationships

1.3 Theory

According to the introduction, Upscaling includes two parts: scale up structure and scale up

properties.

1.3.1 Scale up structure

Because all the three kinds of grids belong to the column layer grid, they have the same theory

of scaling up structure:

1) Generate two-dimensional grid

Within the defined model boundary according to the specified grid parameters

2) Vertically divide the sub-grid blocks

Subdividing each polygon column (i.e., vertical protrusion of an areal polygon) with the

‘structural framework’ according to the desired sedimentary pattern: follow top, follow base

and proportional

3) Obtain the required three-dimensional grid cells

4) Package the cells of the gird, and add the geometric and topological information

Fig. 1-3 Scale up structure.

1.3.2 Scale up properties

After scaling up structure, under the guidance of geometry and topology, properties upscaling

is to find relevant data according to the spatial location, and then scale up properties using geo-

statistics algorithm.

1.4 Work flow

First scale up structure, then fill the cells of the grid with property values, called scale up

properties, and finally export files which are applied to numerical simulation (Fig. 1-4).

Fig. 1-4 Work flow

1.4.1 Scale up structure

Define the new layering scheme (numbers and shapes of layers) and grid size of the simulation

grid. In DepthInsight, both structure model and reservoir model can be selected to be a source

model.

1.4.2 Scale up Properties

Properties from one grid can be transferred to another grid of a different resolution or

orientation. This is usually done in the context of building a simulation model from a geological

model, where the simulation model has been coarsened and reoriented for flow simulation.

A variety of conventional upscaling algorithms are supported, including: Arithmetic mean,

Harmonic mean, Geometric mean, Root-mean-square, Median, Minimum, Maximum, Mid

point, Most of.

1.4.3 Export simulation files

As a numerical simulation pre-processing tool, it is available to export simulation files in

Eclipse format.

1.4.4 Load, display and edit simulation results

Also as a numerical simulation post-processing tool, the simulation results can be loaded back

and edited in this module.

2 How to build numerical simulation grid

As mentioned before, three types of grid can be generated in this module, including PEBI grid,

Rectangular grid and Stair-step grid. Each grid has the unique method to establish.

2.1 Stair-step grid

2.1.1 Generate structure gird

1) Switch to numerical simulation gridding module before generating simulation grid

Click on the icon on the tool bar.

2) Create a new model

(1) Right click on the Tree Pane, and select Create model.

(2) Specify the gird type, PEBI, Rectangular or Stair-step. In the pop-up dialog, choose the

grid to be generated. Select stair-step grid, the settings above would appear in pale grey.

Fig. 2-1 Create a new model

Note: Either structural model or reservoir geological model can be selected to be scaled up.

3) Create model boundary

(1) Right click on the new created model, and select Define border.

(2) Left click on the 3D display window to create new point; right click to undo; double-left

click to finish.

Note: This step is not only a process of creating model boundary, but a process of assigning the

I- and J- directions for stair-step grid and rectangular grid.

If no boundary is given, the area of the gird model is the same as the structural model or

reservoir model.

4) Generate structure grid

(1) Right click on the new created model, and select Generate Grid

(2) In the pop-up dialog, specify the settings for re-gridding, like zones to be scaled up,

layering method and number, grid size

(3) Click OK

Fig. 2-2 Generate structure grid.

Vertical interval: It requires that the horizon sequence must be continuous. The box

checked means the horizon will be used.

Division: Options on how to subdivide the zone into cell layers. Currently, there are three

ways:

Proportional - Constant number of cell layers at every pillar of the grid. The cell

layering will be somewhat conformed to both the top and base of the zone.

Follow top - Cell layering parallel to the top of the zone.

Follow base - Cell layering parallel to the bottom of the zone

Number of layers/Layer thickness: Each zone contains how many layers or the

thickness of each layer.

I increment: Model resolution in I direction.

J increment: Model resolution in J direction

Coarsening: A Coarsening factor can be used to create a geometry that honors the input

grid extents but with multiples of the grid increments. In this way seismic trace locations

can be honored on the coarse grid.


(1) Right click on Properties, a node under the name of new created stair-step model, and

select New property.

Fig. 2-3 Create new property

(2) In the popup dialog, specify the settings for the new created property.

(3) Right click on the model name and select Upscale property

(4) In the popup dialog, select the property to be scaled up and its source model, averaging

method

(5) Colors can be edited in the Property pane of the corresponding property.

Fig. 2-4 Set coarsening parameters

Model type: The new created model is either continuous property, named Property, or

discrete property, named Facies. As long as a template is chosen, it would appear in pale

grey.

Default: Assign a value for the property to make it homogeneous.

Template: Define the type of the new property. There are Porosity, Permeability, Water

saturation, Oil saturation, etc.,

Upscale: Useful when scaling up the property, if the box is checked.

Source: Select the corresponding reservoir property model from which the property is

scaled up into the target model.

Method: Most properties are appropriately upscaled by averaging values from the fine

grid onto the coarser cells of the target grid.

Target: It is the model stores the upscaled property.

Use weight: When using averaging to upscale, other source grid properties can be used

as weighting factors for the source property values

Fill value in all grid: Fill the grid with zero if there is no property value in the

corresponding grids in the reservoir model.


Each cell of stair-step grid generated by DepthInsight is an exact truncated cell that is formed

by dividing polygon column with faults and layers from stratigraphy layering. Each cell is a

polyhedron.

In this module, the simulation files exported is in the format *.grdecl, which can be used in

the Schlumberger Eclipse software. Meantime, stair-step grid can also be exported in Resqml

format in the Structural Modeling Module, which can be imported into Schlumberger Petrel

software.

Right click on the name of stair-step grid and select Export.

2.2 PEBI grid

In DepthInsight, PEBI grid is designed to honor with well perforations. If there are well

perforations data in the model, PEBI grid will be local refined around the wells.

Fig. 2-5 PEBI grid

Well information, including well location, well path and well perforations, is invoked from

well management module when activating the functions-- load well and load perforation.

2.1 Generate structure grid


See generate structure grid（stair-step grid）


See generate structure grid (stair-step grid）


(1) Right click on the new created model, and select Define model boundary


click to finish.




reservoir model.

4) Generate two dimensional grids

(1) Right click on Scheme sets and select New.

(2) Right click on the new scheme named Scheme_1, and select Load well and Load

perforating in sequence.

Fig. 2-6 Load well.

(3) Right click on PEBI grid and select Generate two dimensional grid.

The grid size can be defined in the Properties pane. It is located on the right side of the

interface when the PEBI grid node is selected.

Fig. 2-7 Define the grid size

Maximum size: The largest grid size

Iterations: The calculation times

Circle radius: The grid size of the circle center

Radial layers: The number of layers in the radial direction

Number of proportional division of circumference: Slice number of the circle

Radial radius growth rate: The ratio between radius of this circle and its previous one

Perforation extending direction of the grid spacing: The grid size in the direction which

is perpendicular to horizontal well path.


(1) Right click on the name of the PEBI grid and select Scale up structure.

As mentioned above, grids can be regenerated from structural model or reservoir model. In the

figures below, the first shows the dialog of making layers based on structural model; the second

shows the dialog of making layers based on reservoir model.

Fig. 2-8 Vertically divide the sub-grid blocks

6) Generate three dimensional grid

Right click on the name of the PEBI grid and select Make numerical simulation grid.

2.3 Scale up properties

(1) Right click on Simulation zone sets and select Extract properties.

Fig. 2-9 Extract properties

Extract: If the box is checked, this property is Useful when scaling up the property,

Property name: It is the model stores the upscaled property

Property model: Select the corresponding reservoir property model from which the

property is scaled up.

Note: After scaling up properties, switch to the model name node, the property to be displayed

is chosen here and colors can be edited in its property pane.

Fig. 2-10 Set the property’s color

2.3 Export simulation files

Right click on Simulation zone sets and select Export numerical simulation files.

Fig. 2-11 Export modulus grid

2.4 Truncated rectangular grid

Each cell of truncated rectangle grid generated by DepthInsight is an exact truncated cell that

is formed by dividing polygon column with faults and layers from stratigraphy layering. Each

cell is a polyhedron.

2.4.1 Generate structure grid


See generate structure grid（PEBI grid）


See generate structure grid（PEBI grid）


(1) Right click on Rectangular grid, a node under the name of rectangular model, and select

Define numerical simulation region.


click to finish.




reservoir model.

4) Generate two dimensional grid

Right click on Rectangular grid, a node under the name of rectangular model, and select

Define numerical simulation region.


Right click on the name of the rectangular grid and select Scale up structure.

6) Generate three dimensional grid

(1) Right click on the name of the rectangular grid and select Make numerical simulation grid.

Note: The I-direction could be arbitrary, and it is defined by creating the polygon at different

angle.

(2) The grid size can be defined in the Properties pane. It is located on the right side of the

interface when the Rectangular grid node is selected.

Fig. 2-12 Define the grid size

I direction number of grids: The cell number in I-direction

J-direction number of grids: The cell number in I-direction


See Scale up properties (PEBI grid)


See Export simulation files (PEBI grid)

3 Special topics

3.1 Make local grids

The Make local grids process allows the user to specify a locally enhanced grid definition,

known as a local grid refinement. This enables the user to increase the model resolution near

wells, inside a region of interest.

A simulation project can involve the use of several smaller models, such as cross-sections and

single well models. You can use these to examine the fine-scale performance of part of a field,

for example, the performance in the vicinity of a well. Moving to a full field simulation model

generally means having to use a coarser simulation grid, and these fine-scale effects are lost in

the process. One way of including these fine-scale effects in a full field simulation model is to

refine the parts of interest in the global grid by creating a set of local grids and refining the

gridding within each local grid in the set.

You can create more than one set of local grids in a given global grid and associate one of these

sets in a Simulation case. By generating several cases using differing grid sets, you can compare

the simulation effects of using different local grids and refinements.

How to make local grid

(1) Right click on Local grid sets and then select New

(2) Right click on the new created node and select either Draw polygon or Select well

(3) If Draw polygon is selected, create a closed polygon in the 3D window following the

messages in the information bar; if Select well is activated, choose a well which displays in the

3D window.

Note: Wells are organized in Well Management Module, so it is required to switch to well

management module to check the box in front of Well management node.

(4) Then right click on the new created node and select Generate, in the pop-up dialog select

the method, subdivisions number and interest zones.

(5) Click on Generate.

Fig. 3-1 Generate local grid

Subdivision type: Choose the method you want to use to create the local grid from the

parameters supplied

Nx, Ny, Nz

Enter the number of subdivisions which will be applied in the X, Y and Z directions to each

cell within the host-cell set when Grid number refinement method is selected. The default

value is 2 for all, but you can enter any (reasonably high) positive value.

Dx, Dy, Dz

Enter the maximum subdivision sizes which will be applied in the X, Y and Z directions to

each cell within the host-cell set when Grid size refinement method is selected. The fields

are empty by default which corresponds to no subdivision in each respective direction; You

have to specify at least one (reasonably small) positive value.

Extend host cells along: Select these options (I,J,K) to extend the host-cell set in the

chosen direction. The default is always to extend in K.

Search radius: Enter the distance from the selected well within which all found host cells

will be refined using the chosen method. The unit for this value is determined by the project

unit system.

Zone and region: Check the box if this zone is designed to be refined, but make sure

zones are continuous.

user guide of numerical simulation gridding v2.2.0

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