6 Velocity Modeling
Short Description
Velocity Modeling...
Description
SKUA® and GOCAD® User Guide
Part VI: Velocity Modeling
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Published October 10, 2012
Contents
Part VI: Velocity Modeling Chapter 1
Chapter 2
Introduction to Velocity Modeling ........................................................... 1-1 1.1
What Is Velocity Modeling? ........................................................................... 1-2
1.2
Why Perform Velocity Modeling in SKUA or GOCAD ...................................... 1-3
1.3
Typical Velocity Modeling Workflow............................................................... 1-4
Constructing 3D Models ........................................................................... 2-1 2.1
Constructing a Model3d ............................................................................... 2-2 2.1.1
Common Styles for Models ............................................................... 2-2 Regions ............................................................................................2-2 Layers ...............................................................................................2-3
2.1.2
Procedure to Construct a Model3d ................................................... 2-3
2.1.3
Creating a New Model3d From Surfaces............................................ 2-4
2.1.4
Creating a New Model3D from a SKUA Model................................... 2-5
2.1.5
Adding Surfaces to a Model3d.......................................................... 2-7
2.1.6
Deleting Surfaces from a Model3d .................................................... 2-8
2.1.7
Building a Model3d .......................................................................... 2-8
2.1.8
Rebuilding a Model3d ...................................................................... 2-9
2.1.9
Editing a Model3d............................................................................ 2-9 Making Surfaces and Regions Geologically Consistent ........................2-9 Removing Free Horizon Extremities in a Given Region .......................2-11 Removing All Free Extremities from a Horizon ...................................2-12
2.1.10 Creating and Working with Layers in a Velocity Model ......................2-12 Creating Default Layers in a Velocity Model ......................................2-13 Creating a Layer from a Region in a Velocity Model ..........................2-13 Deleting a Layer in a Velocity Model.................................................2-14 Renaming a Layer in a Model3d .......................................................2-14
Contents
iii
2.1.11 Working with Regions in a Model3d................................................ 2-15 Adding a Region to a Velocity Model Layer ...................................... 2-15 Moving a Region to a Different Velocity Model Layer ....................... 2-15 Deleting a Region from a Velocity Model Layer ................................ 2-16 Finding a Region Name in a Velocity Model ..................................... 2-16 Renaming a Region in a Velocity Model ........................................... 2-17 2.2
Constructing a Voxet Model ........................................................................ 2-18 2.2.1
Procedure to Construct a Voxet Model ............................................ 2-18
2.2.2
Adding Surfaces to a Voxet Model Build List .................................... 2-19
2.2.3
Removing Surfaces from a Voxet Model Build List ............................ 2-20
2.2.4
Building a Voxet Model................................................................... 2-21
2.2.5
Creating and Working with Layers in a Voxet Model ........................ 2-21
2.2.6
Working with Regions in a Voxet Model .......................................... 2-22 Finding a Region Name ................................................................... 2-22 Collapsing Small Regions in a Voxet Model ...................................... 2-22
2.2.7
Chapter 3
Creating Velocity Functions ...................................................................... 3-1 3.1
About Velocity Functions ............................................................................... 3-2
3.2
Creating Velocity Functions from a SKUA Model ............................................. 3-4
3.3
Visualizing Velocity Functions ........................................................................ 3-5
3.4
Creating Velocity Functions for Time-to-Depth Conversion .............................. 3-6 3.4.1
Chapter 4
Creating and Editing Voxet Model Properties ................................... 2-22
Creating Velocity Functions from a Well Marker in Depth and a Horizon in Time ................................................................................ 3-6
3.4.2
Creating Velocity Functions from a Time-Depth Well Log .................... 3-7
3.4.3
Creating Velocity Functions from a Vertical Curve .............................. 3-8
Defining Property Values for Velocity Models ......................................... 4-1 4.1
Procedure to Define Velocity Model Property Values ....................................... 4-2
4.2
Understanding the Property Model Editor ...................................................... 4-3 4.2.1
About the Property Model Editor Interface......................................... 4-3
4.2.2
Working with the Variable Type Menu ............................................... 4-4
4.2.3
Common Variable Definition Parameters............................................ 4-6 Variable Name.................................................................................. 4-6 Shoot Direction ................................................................................ 4-6 Shoot Position .................................................................................. 4-7 Impact Point .................................................................................... 4-8
4.3
iv
Contents
Defining Layer Property Values Directly .......................................................... 4-9 4.3.1
Assigning Constant Values to Properties or Variables .......................... 4-9
4.3.2
Defining Properties or Variables by Using Linear Functions.................. 4-9
4.3.3
Defining Properties or Variables by Using Interpolation ..................... 4-10
4.3.4
Defining Properties or Variables from Grid Properties ....................... 4-12
4.3.5
Defining Values from Surface or Layer Boundary Properties .............. 4-13
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
Defining Values from Surface Boundaries .........................................4-13 Defining Values from Layer Boundaries.............................................4-14 Notes on Defining Values from Surfaces and Layers ..........................4-18 4.4
Defining Properties or Variables by Using Property Functions..........................4-19 4.4.1
Defining Properties or Variables by Using Linear Functions ................4-20
4.4.2
Defining Properties or Variables by Using Exponential Functions ........4-22
4.4.3
Defining Property Functions by Using Scripts ....................................4-23 About Script Property Functions .......................................................4-23 Creating Script Property Functions ...................................................4-24
4.5
Chapter 5
Visualizing Property Functions ......................................................................4-25 4.5.1
Painting a Voxet with a Velocity Model Property ...............................4-25
4.5.2
Painting a Velocity Function on a Grid ..............................................4-26
4.6
Adding Properties to Velocity Models............................................................4-27
4.7
Deleting Properties from Velocity Models ......................................................4-28
Creating Grid Properties with Geostatistical Functions ........................... 5-1 5.1
Geostatistics System File Formats................................................................... 5-2 5.1.1
GS File ............................................................................................. 5-2 Variogram and Associated Parameters File Format ..............................5-2 GS File Examples ...............................................................................5-3
5.2
5.3
User Guide
5.1.2
Column_Average_Map File ............................................................... 5-4
5.1.3
Scattergram File ............................................................................... 5-4
5.1.4
External_Histogram File .................................................................... 5-5
5.1.5
Facies_Map File ................................................................................ 5-5
5.1.6
Annealing_Schedule File ................................................................... 5-5
Estimating Grid Properties with Kriging Algorithms ........................................ 5-6 5.2.1
Estimating Properties with Kriging .................................................... 5-6
5.2.2
Estimating Properties with Kriging with Trend .................................... 5-8
5.2.3
Estimating Properties with Kriging with External Drift .......................5-10
5.2.4
Estimating Properties with Bayesian Kriging......................................5-12
5.2.5
Estimating Properties with Collocated Cokriging ...............................5-14
5.2.6
Estimating Properties with Indicator Kriging .....................................5-16
Running Geostatistical Simulations ...............................................................5-18 5.3.1
Running Sequential Gaussian Simulations (SGS) ................................5-18
5.3.2
Running Non-Conditional Sequential Gaussian Simulations ...............5-21
5.3.3
Running Collocated Cokriging Simulations .......................................5-22
5.3.4
Running Sequential Indicator Simulations (SIS)..................................5-24
5.3.5
Running Annealing Simulations .......................................................5-26
5.3.6
Running Cloud Transform Simulations with P-Fields ..........................5-29
5.3.7
Performing Categorical Histogram Corrections .................................5-31
5.3.8
Performing Continuous Histogram Corrections .................................5-32
5.3.9
Filling Grids with Facies Map Data....................................................5-34
Contents
v
Chapter 6
Chapter 7
Chapter 8
vi
Contents
Performing Velocity Conversions ............................................................. 6-1 6.1
Converting the Velocity Type in One Domain .................................................. 6-2
6.2
Converting the Velocity Type in Different Domains.......................................... 6-3
6.3
Converting the Velocity Type of Velocity Functions.......................................... 6-5
Interpolating Velocity ............................................................................... 7-1 7.1
Smoothing a Voxet Property .......................................................................... 7-2
7.2
Interpolating Velocity Linearly Between Surfaces............................................. 7-3
7.3
Extracting the Velocity Trend From a Voxet ..................................................... 7-4
7.4
Extracting the Velocity Trend From a Well Property ......................................... 7-5
Performing Time and Depth Domain Conversions................................... 8-1 8.1
Converting Objects Using a Velocity Cube ...................................................... 8-2
8.2
Converting a Seismic Cube ............................................................................ 8-4
8.3
Reassigning an Object to the Correct Domain ................................................ 8-7
8.4
Converting Seismic Lines ............................................................................... 8-8
8.5
Converting a SKUA Model........................................................................... 8-10
8.6
Rescaling Objects in the Same Domain ......................................................... 8-12 8.6.1
Rescaling Objects in Same Domain .................................................. 8-12
8.6.2
Rescaling a Seismic Cube in Same Domain....................................... 8-13
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
1 Introduction to Velocity Modeling In this chapter
Overview
•
"What Is Velocity Modeling?," page 1-2
•
"Why Perform Velocity Modeling in SKUA or GOCAD," page 1-3
•
"Typical Velocity Modeling Workflow," page 1-4
This section introduces velocity modeling, describes the benefits of using Paradigm™ SKUA® and Paradigm™ GOCAD® to perform velocity modeling, and describes a typical velocity modeling workflow.
1-1
1.1
What Is Velocity Modeling? The main source of imaging data of the subsurface for large areas is seismic. Because seismic data is a measure of the travel time of a sound wave, seismic data provides an image in time of the subsurface. But reservoir engineers, geologists, and drillers need to work in the depth domain to manipulate objects in real space. To convert the data acquired in time, the geophysicists uses a velocity model to convert from the time domain to the depth domain.The basic equation is:
V = DT Where: V = velocity; T = travel time provided by the seismic data; D = well depth. You create the velocity model from the seismic velocity and well data (checkshot, calibrated integrated sonic logs). After you build the velocity model, you can perform the time-to-depth conversion. Velocity modeling is an important step in seismic imaging, especially for complex reservoirs. The greater the complexity of the geological structure, the greater the need for an accurate velocity model at high resolution. SKUA provide the structural model that helps you achieve such a velocity model.
1-2
Introduction to Velocity Modeling
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
1.2
Why Perform Velocity Modeling in SKUA or GOCAD SKUA or GOCAD, through the SKUA Structure and Stratigraphy, Velocity Modeling, and Time-Depth Conversion modules, enables you to create basic to advanced velocity models and then to perform time-to-depth conversions. For information, see:
• • • • • Creating a velocity model based on the SKUA model
When you build the SKUA model, SKUA automatically creates a sealed 3D model. You can use this SKUA model to create a velocity model. A sealed 3D model has the following advantages:
• • • • Creating velocity model using velocity functions Using geostatistics to update the velocity model
"Creating a velocity model based on the SKUA model," page 1-3 "Creating velocity model using velocity functions," page 1-3 "Using geostatistics to update the velocity model," page 1-3 "Converting velocity," page 1-3 "Performing time-to-depth conversion," page 1-3
Layers are automatically generated. Supports unlimited structural complexity. Faults are taken into account. Ability to define any velocity values using mathematical continuous functions.
SKUA and GOCAD support the Velocity Functions object type. You can use Velocity Functions to create a basic velocity model from sparse data where the velocity is interpolated throughout the entire area of interest. Defining the velocity model is iterative. SKUA and GOCAD provides geostatistic tools that help you create and refine the velocity model.
Converting velocity
SKUA and GOCAD provide tools for you to convert velocity from one type to another in same domain or to a different domain. For example, converting RMS velocity to average velocity.
Performing time-todepth conversion
After you finish refining the velocity mode, you can convert your data (seismic cube, interpretation data, for example) from time to depth using simple vertical stretching. If you want to perform migration, you can use Paradigm™ GeoDepth®.
User Guide
1.2 Why Perform Velocity Modeling in SKUA or GOCAD
1-3
1.3
Typical Velocity Modeling Workflow This section describes a typical velocity modeling workflow. Depending on your goals, you can use a different workflow. SKUA and GOCAD support a variety of workflows. Step
Description
1
Import the data needed to perform the time-to-depth conversion:
Import data
• Seismic data • Well data • Interpretation data (faults, horizons, salt bodies) If this data is in the Epos repository, you can import this data from SeisEarth into a SKUA project. For more information about importing, see:
• Part II: Data Import and Export, Chapter 1, "Importing Data." • Part I: Getting Started, Chapter 4, "Sharing Data with Paradigm Applications." 2
Quality check the data
3
Build seismic velocity model
After you import the data, verify the data is correct and consistent. SKUA and GOCAD provide several methods for creating the velocity model:
• Create a basic velocity model using velocity functions. For more information, see "About Velocity Functions" on page 3-2.
• Create a basic to complex velocity model using a 3D model. For more information, see "Creating Velocity Functions from a SKUA Model" on page 3-4. In GOCAD, you need to build the 3D model, and then define a property for the velocity model. For more information, see Part VIII: 3D Grid Building, Chapter 6, "Building a 3D Reservoir Grid in GOCAD," and Chapter 4, "Defining Property Values for Velocity Models." • Create a basic to complex velocity model using a grid and geostatistics. In this approach, you create a geologic grid using the structural data. With geologic grids, you can keep the structural unit information, which is appropriate when working in a layer-cake model. Using the Property Modeling workflow, you can populate the grid using checkshot data as hard data (after you convert the RMS velocity into interval velocity) and then interpolate the interval velocity throughout the grid using geostatistics (like simple kriging).
1-4
4
Calibrate seismic velocity to well data
You can force the velocity model to fit the well markers when you perform a domain conversion.
5
Interpolate velocity (optional)
For more information, see Chapter 7, "Interpolating Velocity."
6
Perform time-todepth conversion
For more information, see Chapter 8, "Converting Objects Using a Velocity Cube."
Introduction to Velocity Modeling
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
2 Constructing 3D Models
In this chapter
Overview
•
"Constructing a Model3d," page 2-2
•
"Constructing a Voxet Model," page 2-18
There are two types of model objects in Paradigm™ SKUA® and Paradigm™ GOCAD ® : the Model3d, which is the main focus of this chapter, and the Voxet model.
2-1
2.1
Constructing a Model3d • • • • • • • • • •
2.1.1
"Common Styles for Models," page 2-2 "Procedure to Construct a Model3d," page 2-3 "Creating a New Model3d From Surfaces," page 2-4 "Creating a New Model3D from a SKUA Model," page 2-5 "Adding Surfaces to a Model3d," page 2-7 "Deleting Surfaces from a Model3d," page 2-8 "Building a Model3d," page 2-8 "Editing a Model3d," page 2-9 "Creating and Working with Layers in a Velocity Model," page 2-12 "Working with Regions in a Model3d," page 2-15
Common Styles for Models There are three sets of styles common to models:
• • •
Regions Layers Fault blocks
Regions In a model object, a region is a closed space bounded by Surfaces and/or the edges (boundaries) of the model.
Figure 2–1 Model region area
Individual regions
If there are any regions in the model, their names appear in the Regions area. You can adjust the styles associated with each region.
2-2
•
Visible. Turns the display of all selected regions on and off.
•
Region check boxes. When the Visible check box is selected, turns the display of individual regions on and off.
•
Region color. Changes the display color of an individual region.
Constructing 3D Models
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
Voxet models are visualized through their parent voxets. (Select the voxet model in the Objects browser, but display the voxet itself in the 3D Viewer.)
Layers A layer is composed of one or more geologically related regions (for example, a layer of sand faulted into two separate bodies). For information on creating and working with layers, see "Creating and Working with Layers in a Velocity Model" on page 2-12. By default, a layer is named after its top bounding surface.This is to follow the geologic convention of naming a surface Top of Something. For example, the name "Top of Miocene" implies that the layer below the Top of Miocene surface is the Miocene layer.
Figure 2–2 Model layer area
Tip If you think that there are layers in your model but they do not appear in the Layers area, there may be leaks in your model (a layer needs to be completely bounded by Surfaces and/or model boundaries).
If there are any layers in the model, their names appear in the lower half of the Layers area. You can adjust the styles associated with each layer.
•
Visible. Turns the display of all selected layers on and off.
•
Layer check boxes. When the Visible check box is selected, turns the display of individual layers on and off.
•
Layer color. Changes the display color of an individual layer.
Voxet Models are visualized through their parent voxets. (Select the Voxet Model in the Objects browser, but display the voxet itself in the 3D Viewer.)
2.1.2
Procedure to Construct a Model3d Table 2–1 outlines the basic functions to facilitate constructing 3D models and modifying them after construction.
Table 2–1 Basic functions for creating and modifying 3D models
User Guide
To do this
See this procedure
Create a Model3d from one or more Surfaces
"Creating a New Model3d From Surfaces" on page 2-4
Create a Model3d from a SKUA model
"Creating a New Model3D from a SKUA Model" on page 2-5
Add Surfaces to the Model3d you created 1
"Adding Surfaces to a Model3d" on page 2-7
Delete or detach Surfaces from the Model3d you created 1
"Deleting Surfaces from a Model3d" on page 2-8
Force an update of the Model3d based on any surface additions, deletions, or detachments 2
"Building a Model3d" on page 2-8
Recreate the Model3d from its input Surfaces 3
"Rebuilding a Model3d" on page 2-9
2.1 Constructing a Model3d
2-3
1. You can choose whether to incorporate the Build function into your changes, prompting the program to recompute and update the model immediately. If you forego an automatic build to save computation time, changes will not take effect until you run the Build function as a separate step. 2. The Build function does not take into account any changes to the input Surfaces themselves. 3. The Rebuild function is most useful when there have been changes to the input Surfaces, and you want to re-cut them.
2.1.3
Creating a New Model3d From Surfaces When you create a new Model from a set of Surfaces, each surface intersects each face of the model, and surfaces may also intersect each other, or "self-intersect" (so that the program can detect regions enclosed by surfaces). This operation can take some time to carry out.
Figure 2–3 Model3d examples
Regular model
To create a new Model3d from a set of Surfaces
2-4
Model with intersecting surfaces
1
Select Surface commands > Model3d > From Surfaces to open the Create Model3d From Surfaces dialog box.
2
In the Name box, type the name of the new model.
3
In the Surfaces box, enter one or more surfaces to use in building the model.
Constructing 3D Models
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
4
If you want to indicate that the surfaces are self-intersecting, select the Self intersection check box. If you clear this check box, the program will compute only the area between each surface and the voxet itself. Note Typically, surfaces are not self-intersecting.
5
If you want the program to define the Model3d borders consistently, select the Define borders check box.
6
If you want the program to update the model immediately when you click OK or Apply, select the Build check box. Note If you select this check box, the cut operations will be run on all surfaces.
7
2.1.4
Click OK or Apply.
Creating a New Model3D from a SKUA Model Use this command to create a Model3d from SKUA horizons, faults, and boundaries.
To create a Model3d from a SKUA model
About merging small throws
User Guide
1
Select Surface commands > Model3d > From SKUA Model to open the CreateModel3d from SKUA Model Horizons, Faults and Boundaries dialog box.
2
In the SKUA Model box, enter the SKUA model to use to create the Model3d.
3
In the Model3d name box, type the name of the Model3d to create.
4
If you want to merge fault and horizon contacts that have a small throw, expand the Advanced area, select the Merge small throw check box, and then in the Max throw box, type a threshold value. When the throw is below the specified threshold, the fault and horizon contacts will be merged. For more information about this option, see "About merging small throws" on page 2-5.
5
Click OK or Apply.
Areas with a very small throw can often cause failures in the construction of the model3D. If you merge the fault throw, the contacts will be collocated in these areas, which simplifies the construction of the Model3D. For an illustration, see Figure 2–4.
2.1 Constructing a Model3d
2-5
Figure 2–4 Merging small throws
Do not merge contacts
Merge contacts
2-6
Constructing 3D Models
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
2.1.5
Adding Surfaces to a Model3d Use this function to add new surfaces to a model after it is created.
To add surfaces to a Model3d
1
Select Surface commands > Model3d > Add Surface to open the Add Surfaces in Model3d dialog box.
2
In the Model3d box, enter one or more existing models to which the surfaces will be added.
3
In the Surfaces box, enter one or more surfaces to be added to the model.
4
If you want to create copies of the added surfaces before modifying their topology (cutting them) to construct the model, select the To copy check box. Note Each copied surface is named according to the convention model name_surface name . For example, if you add a surface H1 to a model m1, the new surface will be called m1_H1.
User Guide
5
If you want the program to update the model immediately when you click OK or Apply, select the Build check box.
6
If you want the program to define the Model3d borders consistently, select the Define borders check box.
7
Click OK or Apply.
2.1 Constructing a Model3d
2-7
2.1.6
Deleting Surfaces from a Model3d Use this function to delete surfaces from a model after it is created.
To delete surfaces from a Model3d
2.1.7
1
Select Surface > Model3d > Kill Surface to open the Kill Surfaces in Model3d dialog box.
2
In the Model3d box, enter one or more existing models from which the surfaces will be deleted.
3
In the Surface surfaces box, enter one or more surfaces to be deleted from the model.
4
If you want the program to update the model immediately when you click OK or Apply, select the Build check box.
5
If you want the program to define the Model3d borders consistently, select the Define borders check box.
6
Click OK or Apply.
Building a Model3d When you run a "build," the program analyzes the types of changes that occurred to the model, such as adding or deleting surfaces, and performs the operations necessary to recompute the model regions. (If only surfaces were deleted, no intersection phase is necessary, and the build should be relatively fast.)
To build a Model3d
2-8
1
Select Surface commands > Model3d > Build to open the Build 3D-Model dialog box.
2
In the Model3d box, enter one or more models to build.
Constructing 3D Models
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
2.1.8
3
If the surfaces in the model are already pre-cut and you want the program to construct the model without finding the intersection between all the surfaces, clear the With cut check box.
4
If you want the program to define the Model3d borders consistently, select the Define borders check box.
5
Click OK to carry out the command and close the dialog box, or click Apply to carry out the command and keep the dialog box open.
Rebuilding a Model3d Using this command, you can recreate a model (see "Creating a New Model3d From Surfaces" on page 2-4), including re-cutting all the input surfaces. The "rebuild" function actually modifies the input data on which the model is built. In contrast, the regular "build" function updates the model only, based on added or deleted input data.
To rebuild a Model3d
2.1.9
1
Select Surface commands > Model3d > Rebuild to open the Rebuild 3D-Model dialog box.
2
In the Model3d box, enter one or more models to rebuild.
3
If you want the program to define the Model3d borders consistently, select the Define borders check box.
4
Click OK or Apply.
Editing a Model3d For information, see:
• • •
"Making Surfaces and Regions Geologically Consistent," page 2-9 "Removing Free Horizon Extremities in a Given Region," page 2-11 "Removing All Free Extremities from a Horizon," page 2-12
Making Surfaces and Regions Geologically Consistent You can use a model to detect geologic inconsistency between geologic surfaces. This function does the following:
User Guide
•
Removes pieces of surfaces which are not geologically correct
•
Removes parts of top surfaces that are inside intrusive regions
2.1 Constructing a Model3d
2-9
•
Removes parts of top surfaces that are above their erosion surfaces (the erosion surface is younger than the horizon, but part of the horizon is above the erosion surface)
•
Automatically rebuilds the model regions
As shown in the left image of Figure 2–5, two horizons of older age than the salt body penetrate the salt volume, splitting the salt region into three regions. The right image displays the results of the "Make surfaces and regions geologically consistent" function. The non-geologic parts have been removed, creating a hole inside the two horizons and a unique region. Important In order for the algorithm to work properly, you need to first set geologic information on all of the different surfaces (see Part IV: Foundation Modeling, "Defining and Working with Geologic Features" on page 8-1). In Figure 2–5, the salt surface was declared an intrusive surface with an age younger than the two top surfaces.
Figure 2–5 Making figures geologically consistent
Before
To make a Model3d geologically consistent
After
1
Select Surface commands > Model3d > More > Make Geological Consistency to open the Make Surfaces and Regions Geologically consistent dialog box.
2
In the Model3d box, enter one or more models to make geologically consistent.
3
Click OK or Apply. Note You need to run the "build" function separately to rebuild the model itself. (See "Building a Model3d" on page 2-8.)
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Part VI: Velocity Modeling
Removing Free Horizon Extremities in a Given Region Use this function to automatically remove free radial edges from all horizon surfaces within one given region of a model. This function can be especially useful for removing free extremities extending outside of the model in the Universe region (see Figure 2–6 for an example).
Figure 2–6 Removing free horizon extremities in a region
Before removing free extremities
To remove free horizon extremities in a given region
User Guide
After removing free extremities
1
Select Surface commands > Model3d > More > Remove Free Extremities to open the Remove Free Horizon Extremities in a given region from Model3d dialog box.
2
In the Model3d box, enter one or more models.
3
In the Region box, enter the name of the region in which horizon extremities will be removed.
4
Click OK or Apply.
2.1 Constructing a Model3d
2-11
Removing All Free Extremities from a Horizon Use this function to automatically remove free radial edges, or extremities, from one horizon surface throughout all regions of a model. This function can be especially useful when the model has been constructed from surfaces in which borders have been extended to ensure intersections between faults and horizons.
Figure 2–7 Removing free extremities from a horizon
Before removing free extremities
To remove all free extremities from a horizon
2.1.10
After removing free extremities
1
Select Surface commands > Model3d > More > Remove Horizon Free Extremities to open the Remove Free Horizon Extremities from Model3d dialog box.
2
In the Model3d box, enter one or more models.
3
In the AtomsSet horizon box, enter the name of the horizon surface from which extremities will be removed.
4
Click OK or Apply.
Creating and Working with Layers in a Velocity Model The first three functions described in this section are valid for both Model3ds and Voxet Models.
• • • •
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"Creating Default Layers in a Velocity Model," page 2-13 "Creating a Layer from a Region in a Velocity Model," page 2-13 "Deleting a Layer in a Velocity Model," page 2-14 "Renaming a Layer in a Model3d," page 2-14
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
Creating Default Layers in a Velocity Model You can automatically compute a default set of layers for a velocity model. This function groups regions into layers by using geologic information attached to the surfaces bounding the regions. To ensure that this function works properly, be sure to set geologic information for fault and boundary surfaces (see Part IV: Foundation Modeling, "Defining and Working with Geologic Features" on page 8-1). If no geologic information is set, all surfaces are assumed to be top surfaces, and the stratigraphic time is computed from the lowest z value of the surface; this can lead to errors in layer computation.
To create a default layer set
1
Select Surface, Voxet, or SGrid commands > Model3d or Model (as applicable) > Create Defaults to open the Create Default LayerSet inside Model dialog box.
2
In the Model box, enter one or more models in which the layer set will be created. Important The model should contain regions.
3
Click OK or Apply.
Creating a Layer from a Region in a Velocity Model Use this function to create a layer from a specific region in a velocity model.
To create a layer from a region
User Guide
1
Select Surface, Voxet, or SGrid commands > Model3d or Model (as applicable) > Create One to open the Create new Layer inside Model from an existing Region dialog box.
2
In the Model box, enter one or more models to which the layer will be added.
3
In the Layer name box, type the name of the new layer.
4
In the Region box, enter the name of the region from which the layer will be created.
5
Click OK or Apply.
2.1 Constructing a Model3d
2-13
Deleting a Layer in a Velocity Model Use this function to delete a layer from a velocity model.
To delete a layer from a velocity model
1
Select Surface, Voxet, or SGrid commands > Model3d or Model (as applicable) > Remove Layer to open the Remove Layer dialog box.
2
In the Model box, enter one or more models from which the layer will be deleted.
3
In the Layer box, enter the layer to be deleted.
4
Click OK or Apply.
Renaming a Layer in a Model3d Use this function to rename a layer in a Model3d.
To change a layer name in a velocity model
2-14
1
Select Surface commands > Model3d > Rename to open the Change Model Layer name dialog box.
2
In the Model box, enter one or more models containing the layer to be renamed.
3
In the Layer box, enter the layer to be renamed.
4
In the New name box, type the new name of the layer.
5
Click OK or Apply.
Constructing 3D Models
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Part VI: Velocity Modeling
2.1.11
Working with Regions in a Model3d Most of the functions described in this section are valid for both Model3ds and Voxet Models. The model is rebuilt automatically after each of these functions.
• • • • •
"Adding a Region to a Velocity Model Layer," page 2-15 "Moving a Region to a Different Velocity Model Layer," page 2-15 "Deleting a Region from a Velocity Model Layer," page 2-16 "Finding a Region Name in a Velocity Model," page 2-16 "Renaming a Region in a Velocity Model," page 2-16
Adding a Region to a Velocity Model Layer Use this function to add a region to a layer within a velocity model.
To add a region to a velocity model layer
1
To open the Add Region to Layer dialog box, select either:
•
Surface commands > Model3d > Region > Add to Layer.
•
Voxet or SGrid commands > Model > Add to Layer.
2
In the Model box, enter one or more models.
3
In the Region box, enter the region to be added to the layer.
4
In the Layer box, enter the destination layer.
5
Click OK or Apply.
Moving a Region to a Different Velocity Model Layer Use this function to move a region to a different layer within a velocity model.
To move a region to a different layer
1
Display the model regions and layers in the 3D Viewer.
2
Select either:
• • 3
User Guide
Surface commands > Model3d > Region > Move to Layer. Voxet or SGrid commands > Model > Move to Layer.
In the 3D Viewer, click the region to be moved, then click the destination layer.
2.1 Constructing a Model3d
2-15
Deleting a Region from a Velocity Model Layer Use this function to delete a region from a layer within a velocity model.
To delete a region from a layer
1
To open the dialog box, select either:
•
Surface commands > Model3d > Region > Remove from Layer.
•
Voxet or SGrid commands > Model > Remove from Layer.
2
In the Model box, enter one or more models.
3
In the Region box, enter the region to be deleted from the layer.
4
In the Layer box, enter the target layer.
5
Click OK or Apply.
Finding a Region Name in a Velocity Model Use this function to find the name of a specific region within a velocity model.
To find the region name of a displayed region
Do one of the following:
Select Voxet or SGrid commands > Model > Region > Find Name, and then click the region in the 3D Viewer. – or – Select Selection toolbar > Get XYZ Coordinate 3D Viewer.
, and then click the region in the
The status bar displays the region name. Region name
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Part VI: Velocity Modeling
Renaming a Region in a Velocity Model Use this function to rename a region within a velocity model.
To rename a region
User Guide
1
To open the Change Model Region name dialog box, select either:
•
Surface commands > Model3d > Region > Rename.
•
Voxet or SGrid commands > Model > Rename.
2
In the Model box, enter one or more models.
3
In the Region box, enter the region to be renamed.
4
In the New name box, type the new name of the region.
5
Click OK or Apply.
2.1 Constructing a Model3d
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2.2
Constructing a Voxet Model For information, see:
• • • • • • •
2.2.1
"Procedure to Construct a Voxet Model," page 2-18 "Adding Surfaces to a Voxet Model Build List," page 2-19 "Removing Surfaces from a Voxet Model Build List," page 2-20 "Building a Voxet Model," page 2-21 "Creating and Working with Layers in a Voxet Model," page 2-21 "Working with Regions in a Voxet Model," page 2-22 "Creating and Editing Voxet Model Properties," page 2-22
Procedure to Construct a Voxet Model Table 2–2 outlines the basic functions to facilitate constructing Voxet Models and modifying them after construction.
Table 2–2 Basic functions for creating and modifying Voxet Models
To do this
See this procedure
Specify the surfaces to be included in the Voxet Model 1
"Adding Surfaces to a Voxet Model Build List" on page 2-19
Exclude surfaces from a Voxet Model 1
"Removing Surfaces from a Voxet Model Build List" on page 2-20
Perform the initial build of the Voxet Model or force an update based on any surface additions or deletions 2
"Building a Voxet Model" on page 2-21
1. You can choose whether to incorporate the Build function into your changes, prompting the program to recompute and update the model immediately. If you forego an automatic build to save computation time, changes will not take effect until you run the Build function as a separate step. 2. The Build function does not take into account any changes to the input surfaces themselves.
For information, see:
• • • • About Voxet Models
"About Voxet Models," page 2-18 "Building effective Voxet Models," page 2-19 "Visualizing Voxet Models," page 2-19 "Voxet Model warnings," page 2-19
When you create a Voxet, an empty Voxet Model is created automatically as well. A Voxet Model is the gridded volume confined within the cage of the Voxet. You can cut the Voxet Model volume with Surfaces to create gridded sub-volumes. A layer is a contiguous subvolume. A Voxet Model, therefore, is a bounded volume that consists of gridded subvolumes called layers. Theoretically, a Voxet Model has at least one layer (the entire Voxet volume), but for practical purposes, a Voxet Model is considered empty until you create at least one subvolume within the model (see "Building a Voxet Model" on page 2-21). Since building a Voxet Model is simpler than building a Model3d, it can be helpful to build a Voxet Model to check the validity of layers before building a Model3d. In an effective Voxet Model, the Voxet should be smaller than all the Surfaces that will to cut the Voxet walls, creating layers.
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Building effective Voxet Models
In the left Voxet in Figure 2–8, all the sub-horizontal Surfaces cut all four walls of the Voxet, and there is room above the top and below the bottom Surface. A Voxet Model built from those Surfaces and the Voxet will have six layers (and six regions in the Voxet). In the right Voxet in Figure 2–8, the Voxet is so big that it does not intersect any of the Surfaces. A Voxet Model built from those Surfaces and the Voxet will have only two layers: the layer inside the middle closed Surface and the layer outside it.
Figure 2–8 Voxet examples
Effective Voxet
Ineffective Voxet
A Voxet created from an object box (see Part IV: Foundation Modeling, "Creating a Voxet from an Objects Box" on page 6-10) is meant to include all objects selected; therefore, we do not recommend building a Voxet Model from that set of objects. To guarantee proper intersections (cutting), create the Voxet from end points (see Part IV: Foundation Modeling, "Creating a Voxet from Corner Points" on page 6-8), in which you can specify the XYZ locations of the Voxet corner points.
Visualizing Voxet Models
Voxet Model warnings
2.2.2
Voxet Models are visualized through their parent Voxets. (Select the Voxet Model in the Style dialog box, but display the Voxet itself in the 3D Viewer.) When you successfully create a layer in a Voxet Model, a region is automatically created in the corresponding Voxet. You can also view the regions in the Voxet to visualize the Voxet Model.
•
When you build a Voxet Model, part of the process is cutting the Voxet with the Surfaces, which cuts the connectivity in the Voxet. (See Part IV: Foundation Modeling, "Cutting a Voxet with Surfaces" on page 6-12.)
•
Once you have built a Voxet Model, do not add or delete a Surface and rebuild (see "Voxet Model warnings" on page 2-19).
Adding Surfaces to a Voxet Model Build List Use this function to specify the Surfaces to be included in a Voxet Model. After specifying the surfaces, you can proceed to build the Voxet Model (see "Building a Voxet Model" on page 2-21), or you can continue to modify the build list by adding or deleting other surfaces. Important Once you have built the Voxet Model, do not add or delete Surfaces and rebuild.
User Guide
2.2 Constructing a Voxet Model
2-19
To add surfaces to the build list of a Voxet Model
1
Display the Voxet and the Surfaces in the 3D Viewer. In order to create valid regions in the model, the Surfaces should cut one another and/or the Voxet walls (see Figure 2–8 on page 2-19).
2
Select Voxet commands > Model > Add Surfaces to open the Add Surfaces to Voxet Model dialog box.
3
In the Voxet box, enter one or more voxets. Note A Voxet Model is always attached to a Voxet.
4
The names of the displayed Surfaces will be listed automatically in the Surface surfaces box.
5
Click OK or Apply. Note The Voxet Model will not actually be built until you execute the Build function (see "Building a Voxet Model" on page 2-21).
2.2.3
Removing Surfaces from a Voxet Model Build List Use this function to specify Surfaces to be excluded from a Voxet Model. After specifying the surfaces, you can proceed to build the Voxet Model (see "Building a Voxet Model" on page 2-21), or you can continue to modify the build list by adding or deleting other surfaces. Important Once you have built the Voxet Model, do not add or delete Surfaces and rebuild.
To remove Surfaces from the build list of a Voxet Model
1
Select Voxet commands > Model > Remove Surfaces to open the Remove Surfaces from Voxet Model dialog box.
2
In the Voxet box, enter one or more voxets. Note A Voxet Model is always attached to a Voxet.
3
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The names of the displayed Surfaces will be listed automatically in the Surface surfaces box.
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Part VI: Velocity Modeling
4
Click OK or Apply. Note The Voxet Model will not actually be built until you execute the Build function (see "Building a Voxet Model" on page 2-21).
2.2.4
Building a Voxet Model Use this function to build a Voxet Model. To build a Voxet Model, you need to first add Surfaces to its build list (see "Adding Surfaces to a Voxet Model Build List" on page 2-19). The Surfaces should intersect one another or the Voxet walls in order to create layers (see Figure 2–8 on page 2-19). Avoid modifying a Voxet Model once you have built it (see "Voxet Model warnings" on page 2-19). Note that Voxet Models are visualized through their parent Voxets. (Select the Voxet Model in the Style dialog box, but display the Voxet itself in the 3D Viewer.) When you successfully create a layer in a Voxet Model, a region is automatically created in the corresponding Voxet. As an option, you can also view the regions in the Voxet to visualize the Voxet Model.
To build a Voxet Model
1
Select Voxet commands > Model > Build to open the Build Voxet Model dialog box.
2
In the Voxet box, enter one or more voxets. Note A Voxet Model is always attached to a Voxet.
Tip Grouping regions into layers automatically can reduce the number of regions dramatically in cases where two surfaces are very close to each other.
3
Important Layer construction relies on the presence of geologic Information for each horizon and fault (see Part IV: Foundation Modeling, Chapter 8, "Defining and Working with Geologic Features."). 4
2.2.5
If you want to construct the layers only, select the Layers only check box. Alternatively, you can construct layers manually (see "Creating Default Layers in a Velocity Model" on page 2-13).
Click OK or Apply.
Creating and Working with Layers in a Voxet Model For information, see "Creating and Working with Layers in a Velocity Model" on page 2-12.
User Guide
2.2 Constructing a Voxet Model
2-21
2.2.6
Working with Regions in a Voxet Model For information, see:
• •
"Finding a Region Name in a Velocity Model," page 2-16 "Collapsing Small Regions in a Voxet Model," page 2-22
Finding a Region Name See "Finding a Region Name in a Velocity Model" on page 2-16
Collapsing Small Regions in a Voxet Model Use this command to modify the topology of a Voxet. This command creates a hole inside the boundary of a small region, which is then absorbed into a larger region and disappears. If the small region was bounded by more than one region, there is no way to control the region into which the small region will be absorbed.
To collapse small regions
1
Select Voxet commands > Model > Remove Small Regions to open the Filter/ Collapse Small Voxet Model Regions dialog box.
2
In the Voxet box, enter one or more voxets. Note A Voxet Model is always attached to a Voxet.
2.2.7
3
In the nb cells box, enter the region threshold size. Every region smaller than the size you specify will be collapsed into neighboring regions.
4
Click OK or Apply.
Creating and Editing Voxet Model Properties For information about other editing commands for Voxet Models, see "Editing a Model3d" on page 2-9. In addition, you can use the Property Model Editor tools with Voxet Models, Model3ds, and SKUA models, as described in Chapter 4, "Defining Property Values for Velocity Models."
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3 Creating Velocity Functions
In this chapter
Overview
•
"About Velocity Functions," page 3-2
•
•
"Creating Velocity Functions from a SKUA Model," page 3-4
"Visualizing Velocity Functions," page 3-5
•
"Creating Velocity Functions for Timeto-Depth Conversion," page 3-6
Paradigm™ SKUA ® and Paradigm™ GOCAD ® provide a Velocity Functions object that you can use to perform time-to-depth conversions. Depending on the data that is available on the velocity function, you can export it to the Epos repository as vertical functions or as pencils. If you generate the velocity functions from a SKUA model, the pencils carry all of the geologic model information that can be shared in Epos-enabled applications, such as Paradigm™ GeoDepth ®. The commands to create velocity functions are available with the Velocity Modeling and Time-Depth Conversion module.
3-1
3.1
About Velocity Functions Velocity functions are geometric objects that you can use in velocity modeling for time-todepth conversion. You can share velocity functions with Epos-enabled applications by exporting them to an Epos database as:
• •
Vertical functions. Contain only velocity properties. Pencils. Contain geologic, structural model information.
Note The vertical functions and pencil data that you import from Epos are stored as velocity functions in SKUA or GOCAD. For more information, see:
• • • What are velocity functions?
"What are velocity functions?," page 3-2 "Properties on velocity functions," page 3-2 "Velocity category," page 3-3
Velocity functions correspond to a set of vertical curves that carry a velocity property (See Figure 3–1). The geometry of the velocity functions is defined by the objects that you use to create them, which can include the following objects:
• • •
From vertical curves From vertical wells From a SKUA model
In SKUA and GOCAD, velocity functions belong to the Velocity category.
Figure 3–1 Velocity Functions object showing the average velocity property shown with seismic in 3D Viewer Velocity functions carrying the average velocity (Vavg)
Properties on velocity functions
3-2
Velocity functions contain property values at the following locations:
• •
Creating Velocity Functions
At their nodes (called properties) On their segments (called edge properties)
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Part VI: Velocity Modeling
Velocity category
In the Objects browser, the category Velocity can contain the following object types that are used in a velocity modeling workflow:
• • •
User Guide
Velocity Functions 3D Surveys Curves
3.1 About Velocity Functions
3-3
3.2
Creating Velocity Functions from a SKUA Model From a SKUA model you can create velocity functions that carry the structural information of the SKUA model (units, boundaries, dip and azimuth). You can then export the velocity functions to the Epos repository and use them in Epos-enabled applications. For example, you can use them in GeoDepth to perform tomography. For more information, see:
• • Prerequisites To create velocity functions from a SKUA model
"Prerequisites," page 3-4 "To create velocity functions from a SKUA model," page 3-4
To use this command, you need a SKUA model and a survey as input data. 1
Select Velocity commands > Velocity Functions > Create from SKUA Model to open the Compute Velocity Functions from SKUA Model dialog box.
2
In the SKUA Model box, select the SKUA model from which you want to create the velocity functions.
3
In the Name box, specify a name for the velocity function output.
4
If you want to use a survey to define the areal sampling of the velocity functions, select the Use survey check box, and then in the Survey box, enter the survey. Otherwise, in the Voxet cube box, enter a voxet cube.
5
In the Inline jump and Crossline jump boxes, type a value of 1 or greater to indicate how many samples to compute. For example, if you accept the default value of 1, all samples are used; If you enter 5, every 5th sample is used and the computed velocity function is less dense.
The command generates a velocity function with X, Y, Z built-in properties and properties computed from the SKUA model (azimuth, dip and boundaries). It also creates the units property (located under edge properties), which is a discrete property that corresponds to the stratigraphic unit of the SKUA model. The velocity function has the same domain as the SKUA model.
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Part VI: Velocity Modeling
3.3
Visualizing Velocity Functions In the 3D Viewer, you can visualize velocity functions that you create from a SKUA model. For more information, see:
• • To slice a velocity function
"To slice a velocity function," page 3-5 "To change the velocity function display," page 3-5
You can use the Slicer toolbar to "slice" a velocity function in the 3D Viewer so that you can examine it. 1
In the Objects browser, select the velocity function to display it in the 3D Viewer.
2
On the Slicer toolbar, click Slicer
to turn on the slicer.
The slicer displays the outline of a box around the velocity function displayed in the 3D Viewer. The slicer limits the view in the 3D Viewer to the volume of the slicer box. For more information about using the Slicer toolbar, see Part III: Visualization, "Slicer Toolbar" on page 3-8.
To change the velocity function display
User Guide
Using styles, you can display the velocity function by sections and by selected horizon and fault boundaries. 1
Right-click the velocity function and select Style > Editor to open the Style dialog box.
2
From the Graphic tab, use the axis-1 and axis-2 boxes to change the velocity function section that is displayed in the 3D Viewer.
3
To display the velocity function only within a specified horizon or fault boundary, in the Boundaries area, select the horizon or fault, and then select the Show only check box.
3.3 Visualizing Velocity Functions
3-5
3.4
Creating Velocity Functions for Time-toDepth Conversion You can use velocity functions to perform a time-to-depth conversion. With velocity functions, you can perform a time-to-depth conversion of a full volume even when there is sparse data (SKUA or GOCAD interpolates when there is sparse data). Thus, you can easily generate an initial, approximate time-to-depth conversion without needing to create a complex velocity model. For more information, see:
• • •
3.4.1
"Creating Velocity Functions from a Well Marker in Depth and a Horizon in Time," page 3-6 "Creating Velocity Functions from a Time-Depth Well Log," page 3-7 "Creating Velocity Functions from a Vertical Curve," page 3-8
Creating Velocity Functions from a Well Marker in Depth and a Horizon in Time You can create velocity functions with an average velocity computed from the input data (well marker in depth and calibrated horizon in time). It allows you to easily generate an initial velocity model to perform time-to-depth conversion. For more information, see:
• • Prerequisites To create velocity functions from depth markers and horizon in time
3-6
"Prerequisites," page 3-6 "To create velocity functions from depth markers and horizon in time," page 3-6
To use this command, you need well markers in depth and horizons in time as input data. 1
Select Velocity commands > Velocity Functions > Create from Calibrated Markers and Horizons to open the Create Velocity Functions from well markers and time horizons dialog box.
2
In the Name box, specify the name of the velocity functions to create.
3
In the Wells box, select the wells in depth that contain the markers that will be matched to the time horizons.
4
In the Object Horizons box, select the time horizons. The time horizons can be a Surface, 2D-Grid, or Horizon Grid object.
Creating Velocity Functions
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Part VI: Velocity Modeling
As shown in Figure 3–2, the command generates two velocity functions (one in depth domain and one in time domain). The velocity function properties are:
•
X, Y, Z built-in properties
•
Vavg. The average velocity computed from the input data.
SKUA or GOCAD computes the average velocity for the well markers and horizons that share the same feature as follows:
Vavg = 2 Depth marker Surface time Where:
Depth marker Surface time
= the depth value of the well marker
= the two-way seismic time
The command automatically handles unit conversion.
Figure 3–2 Velocity Function in Objects browser
Velocity functions
3.4.2
Creating Velocity Functions from a TimeDepth Well Log You can create velocity functions from a two-way-time (TWT) well log. For more information, see:
• •
User Guide
"Prerequisites," page 3-6 "To create velocity functions from a Time-Depth well log," page 3-8
3.4 Creating Velocity Functions for Time-to-Depth Conversion
3-7
Prerequisites To create velocity functions from a Time-Depth well log
To use this command, you need wells in depth with a time-depth log as input data. 1
Select Velocity commands > Velocity Functions > Create from T-D Well Curves to open the Create Velocity Functions from Time/Depth Logs dialog box.
2
In the Name box, specify a name for the velocity functions to create.
3
In the Wells box, enter wells in the depth domain that carry a time log.
4
In the Time/Depth Log box, select the time log.
5
To create the velocity functions in the time domain, select the Create Velocity Functions in Time Domain check box.
The command generates a velocity functions in the domain of the well (unless you select the Create Velocity Functions in Time Domain check box). It creates a function at every well KB location and a vertical point at every curve point (point on the time-depth log). The velocity function properties are:
3.4.3
•
X, Y, Z built-in properties
•
Vavg. The average velocity computed from the depth information of the well path and the time log.
Creating Velocity Functions from a Vertical Curve You can create velocity functions from vertical curves . For more information, see:
• •
3-8
Creating Velocity Functions
"Prerequisites," page 3-9 "To create velocity functions from curves," page 3-9
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Part VI: Velocity Modeling
Prerequisites To create velocity functions from curves
To use this command, you need vertical curves with a velocity property as input data. 1
Select Velocity commands > Velocity Functions > Create from Vertical Curve to open the Create Velocity Functions from Curves dialog box.
2
In the Curve box, select the curves on which to compute the velocity functions. Note If you select a non vertical curve, the command does not create velocity functions.
3
In the Name box, specify a name for the velocity functions.
This command transforms the vertical curve objects into a Velocity Functions object and transfers all of the curve object properties onto the Velocity Functions object. The sampling of the curves defines the sampling of the velocity function. The created velocity functions have the domain of the curve object.
User Guide
3.4 Creating Velocity Functions for Time-to-Depth Conversion
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4 Defining Property Values for Velocity Models In this chapter
•
"Procedure to Define Velocity Model Property Values," page 4-2
• • •
Overview
•
"Understanding the Property Model Editor," page 4-3
"Defining Properties or Variables by Using Property Functions," page 4-19
•
"Working with the Variable Type Menu," page 4-4
"Visualizing Property Functions," page 4-25
•
"Defining Layer Property Values Directly," page 4-9
"Adding Properties to Velocity Models," page 4-27
•
"Deleting Properties from Velocity Models," page 4-28
In a velocity model such as a Model3d or a Voxet model, properties cannot be attached to data points (as in geometric objects) because there is no connection between the Surfaces. Instead, you can use the Property Model Editor in Paradigm™ SKUA ® and Paradigm™ GOCAD ® to define property values (such as velocity) for each model layer through mathematical methods including constants, variables, and functions. Functions, which vary in complexity, can in turn include elements such as defined variable, the properties and xyz-positions of nearby Voxets and Surfaces, mathematical equations, and so on.
4-1
4.1 Table 4–1 Workflow for defining property values
4-2
Procedure to Define Velocity Model Property Values For this step
See
1
Create a velocity model with regions
"Constructing a Model3d" on page 2-2 "Constructing a Voxet Model" on page 2-18
2
Create layers in the velocity model
"Creating and Working with Layers in a Velocity Model" on page 2-12
3
Create global properties (property names) for the velocity model
"Adding Properties to Velocity Models" on page 4-27
4
Define property values for the layers using the Property Model Editor
"Defining Layer Property Values Directly" on page 4-9 "Defining Properties or Variables by Using Property Functions" on page 4-19
Defining Property Values for Velocity Models
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4.2
Understanding the Property Model Editor • • •
4.2.1
"About the Property Model Editor Interface," page 4-3 "Working with the Variable Type Menu," page 4-4 "Common Variable Definition Parameters," page 4-6
About the Property Model Editor Interface The Property Model Editor is a tool for creating property values (such as velocity) for the various layers of a model. The Property Model Editor (see Figure 4–1) is composed of three main areas: the model selector, the property browser, and the value definition area. You can also use the Property Model Editor to review any existing properties or variables for the layers within the model.
Figure 4–1 Property Model Editor Model selector
Commands
Property list
Variable type
Value definition
To open the Property Model Editor
User Guide
1
To open the dialog box, do either of these:
•
Select Surface, Voxet, or SGrid commands > Model3d or Model (as applicable) > Editor.
•
In the Objects browser, right-click any velocity model property > select Editor.
4.2 Understanding the Property Model Editor
4-3
2
In the Model box, enter the velocity model for which you want to define properties.
Important Ensure that the velocity model contains, at a minimum, regions and layers. For more information, see Table 4–1 on page 4-2.
4.2.2
Working with the Variable Type Menu You can define property values for the layers in your model by using constants, variables, and functions. Functions, which vary in complexity, can in turn include elements such as defined variables ("intermediate variables"), the properties and xyz-positions of nearby Voxets and Surfaces, mathematical equations, and so on.
Figure 4–2 Property browser Global property Layer
Variable
Tip A special layer called Everywhere facilitates creating variables that will be available in all layers, and a special Property Model called All Properties enables the creation of variables that will be available in all Property Models.
Layer-specific properties
When you create a new property, it is global, or applicable to the whole model (see Figure 4–2). Every layer in the model will contain the property, but the layer-specific values are initially undefined. You need to define properties for each layer individually, as the different layers in a model do not share property functions or variables. Since variables or functions that you define in one layer do not apply to other layers, you can duplicate the same variable and function names in different layers. Use the Add Variable, Remove Variable, and Add Property commands to:
• •
Create properties for the model, if you have not already done so (for information, see "Adding Properties to Velocity Models" on page 4-27) Create or delete variables or functions that define property values Note You can define a variable either as a separate step or "on demand," while filling out the value definition area (shown in Figure 4–1 on page 4-3).
The value definition area displays the details of the property or variable definition selected in the Variable type box. This menu of value definition types contains:
• • Table 4–2 Variable definitions
Five options to define layer property values directly (see "Defining Layer Property Values Directly" on page 4-9) Three options to define layer property values using property functions (see "Defining Properties or Variables by Using Property Functions" on page 4-19)
Variable definition
For information, see
Undefined Build In Constant
"Assigning Constant Values to Properties or Variables," page 4-9
Linear Function
"Defining Properties or Variables by Using Linear Functions," page 4-20
Exponential Function
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To define a property or variable (overview)
Variable definition
For information, see
Script
"Defining Property Functions by Using Scripts," page 4-23
Linear Function of Property
"Defining Properties or Variables by Using Linear Functions," page 4-9
Interpolated Property
"Defining Properties or Variables by Using Interpolation," page 4-10
From Grid Property
"Defining Properties or Variables from Grid Properties," page 4-12
From Surface or Layer Boundary Property
"Defining Values from Surface or Layer Boundary Properties," page 4-13
1
If you need to create a new variable, do the following: Note You can define a variable either as a separate step or "on demand," while filling out the value definition area.
a
In the property browser (see Figure 4–2), click the layer to which the variable will belong.
b
Click Add Variable to open the Variable Name dialog box.
c
In the Name box, type the name of the new variable, and then Click OK.
The new variable appears in the property browser. 2
In the property browser, click the property or variable that you want to define or edit.
3
If you are defining the property or variable for the first time, select an option in the Variable type box. (The default variable type is as Undefined.) Note Each option in the Variable type box brings up a different panel, as indicated in Figure 4–2.
User Guide
4
Define the parameters of the selected option in the value definition area. (See "Defining Layer Property Values Directly" on page 4-9 or "Defining Properties or Variables by Using Property Functions" on page 4-19.)
5
Click Update Variable Definition to apply your changes.
4.2 Understanding the Property Model Editor
4-5
4.2.3
Common Variable Definition Parameters Many property/variable definition options share the following common parameters or concepts:
• • • •
"Variable Name," page 4-6 "Shoot Direction," page 4-6 "Shoot Position," page 4-7 "Impact Point," page 4-8
Variable Name Direct property definitions
If you are defining a layer property directly using one of the options in the Variable type menu, ensure that the Variable name displayed matches the name of the layer property you are defining; otherwise, the program assumes that you are defining an intermediate variable to be used in a property function (see "Defining Properties or Variables by Using Property Functions" on page 4-19).
Intermediate variables
If you are defining an intermediate variable to be used in a property function, ensure that the Variable name displayed is different than the name of the layer property; otherwise, the program assumes that you are defining the layer property itself.
Variables in different layers
When you create (define) a variable, it is associated with a specific layer and property, outside of which it has no meaning. If you want to use the variable in any other layers, you need to recreate the variable in the other layers. Since the various layers do not share data, you can duplicate the same variable and function names in different layers.
Shoot Direction Shoot direction, which is also known as the search direction or dir_Z, specifies the direction along which to search for impact points (see "Impact Point" on page 4-8). There are four shooting directions, but not all of them are available in every menu. In the Property Model Editor, only the first three are available; in the Constraints menu (in the Surface commands), only the fourth is available.
dir_Z = +1
The command searches in the positive Z (up) direction from the shoot position (see "Shoot Position" on page 4-7), as shown in Figure 4–3 (b).
dir_Z = -1
The command searches in the negative Z (down) direction from the shoot position, as shown in Figure 4–3 (b).
two_way
The command searches in both the positive and negative Z directions from the shoot position, as shown in Figure 4–3 (a). This option overwrites the dir_Z = +1 or dir_Z = -1 options. When shooting two ways, you can only shoot from inside (see "from_inside" on page 4-7).
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dir_XYZ
The command shoots along the direction specified by the vector dir_XYZ. (Actually, the command shoots along both the positive and negative directions specified by this shoot position.)
Figure 4–3 Shooting direction/shooting point combinations
a
b
c
two_way
dir_z = -1
dir_z = +1
from_inside
from_inside
from_inside
c
d
dir_Z = +1
dir_Z = -1
from_outside
from_outside
Shoot Position Shoot position is also known as the shooting point. This parameter, which is used with the Add Variable command only, defines the starting point of the shoot (search). There are two shoot position options: from_inside and from_outside (in dialog boxes, you select from_outside by clearing the from_inside check box or option). See Figure 4–3 on page 4-7.
from_inside
The command searches from the given point in the layer for which you are defining a property variable, along the specified shoot direction to search for the specified source object(s). (See a, b, and c in Figure 4–3 on page 4-7.) When shooting two ways (see "two_way" on page 4-6), you can only search from inside.
from_outside
User Guide
The command first gets outside of the layer from the given point (along the direction opposite the specified shoot direction). Once outside the layer, the command keeps moving (along the direction opposite to the specified shoot direction) until it reaches a point below (or above, if the shoot direction is Z-) all points in the given layer. (See c and d in Figure 4–3 on page 4-7.) The command then shoots from that outside point, along the specified shoot direction, to look for an impact point on the specified source object(s).
4.2 Understanding the Property Model Editor
4-7
Impact Point The impact point is the first point encountered on the specified source object(s) along the specified shoot direction. In some geologic formations (such as folded or thrusted surfaces), there can be more than one intersection between the shooting path and the specified source object(s) (see the left illustration in Figure 4–4, dir_Z = -1). Only the first of such intersections is the impact point. Actually, the command stops searching in that particular direction once it finds an intersection.
Multiple impact points
If the shoot direction is two-way, but only one impact point is needed, the command searches in both directions to find impact points. It will keep the closest one if it finds two (one in each direction).
Figure 4–4 Impact points and the geometry of the source Surface
X
X X
X X X
X
dir_Z = -1
dir_Z = 1
points in the layer dir_shoot source surface (the surface with the property you want)
X No impact point
impact points on the source surface
If the command does not find an impact point along the specified shoot direction(s) for a given point in the model layer, the value of that particular variable at that point is null. See the right illustration in Figure 4–4, dir_Z = 1. The following are illustrations of how the command finds the impact points under different circumstances:
• • • •
4-8
Figure Figure Figure Figure
4–5 4–6 4–7 4–8
on on on on
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4.3
Defining Layer Property Values Directly For information, see:
• • • • •
4.3.1 To assign a constant value to a property or variable
4.3.2
"Assigning Constant Values to Properties or Variables," page 4-9 "Defining Properties or Variables by Using Linear Functions," page 4-9 "Defining Properties or Variables by Using Interpolation," page 4-10 "Defining Properties or Variables from Grid Properties," page 4-12 "Defining Values from Surface or Layer Boundary Properties," page 4-13
Assigning Constant Values to Properties or Variables 1
In the property browser, click the property or variable that you want to define or edit.
2
In the Variable type box, select Constant.
3
In the Constant value box, type a numerical constant value to assign to the variable.
4
Click Update Variable Definition to apply your changes.
Defining Properties or Variables by Using Linear Functions This definition option is similar to defining property variables by using interpolation (see "Defining Properties or Variables by Using Interpolation," page 4-10), except that the top and bottom Surfaces are replaced by the upper and lower bounding Surfaces of a model layer. This definition option can be useful when there is more than one top and/or more than one bottom bounding Surface for the layer of interest. This definition option ensures that at any given point in the selected layer, the variable will find two impact points to get an interpolated (extrapolated) Value, since a layer, by definition, is completely bounded. (There is one exception: when part of the bounding surface of the given layer is the bounding box of the model, the command may not be able to locate an impact point.)
User Guide
4.3 Defining Layer Property Values Directly
4-9
To define a property or variable by using a linear function
1
In the property browser, click the property or variable that you want to define or edit.
2
In the Variable type box, select Linear Function of Property.
3
In the Referenced layer box, select the name of the referenced layer whose bounding Surfaces will be the source Surfaces. Important Ensure that the property you want is defined on all of those Surfaces.
4.3.3
4
In the Referenced property box, enter the name of the property on the bounding Surfaces of the selected referenced layer. (This does not have to be the same name as the name of the variable or the name of the layer property.)
5
If you want to add a constant value to the referenced property, type a number in the Value to add to referenced property box.
6
If you want to multiply the referenced property by a constant scaling factor, type a number in the Scaling factor (multiple) to apply to referenced property box.
7
Click Update Variable Definition to apply your changes.
Defining Properties or Variables by Using Interpolation This definition option finds the property values at two impact points (see "Impact Point" on page 4-8), one from each of the two specified source boundaries, and performs a linear interpolation (or extrapolation) to find a value for the variable at (x, y, z). The command finds the top and bottom impact points by shooting two ways (see "two_way" on page 4-6) to the top source boundary and the bottom boundary surface from the given point (see "from_inside" on page 4-7). Figure 4–5 presents graphic examples of where impact points may be located. The terms "top source Surface" and "bottom source Surface" do not imply relative positions to each other or to the selected model layer. The terms are only used to remind you that you need two source Surfaces.
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Figure 4–5 Finding the two impact points on the two source Surfaces for a given point in a model layer
Top source surface
Model layer
Top source surface
X
XX
Model layer
X
X X
X
X X
Bottom source surface
X
Bottom source surface
Each boundary property is defined as a function:
X X
P x y z = P o + Z – Z o
Where P(x,y,z) is the linear property function, Z is the coordinate at a given set of (x,y,z) points, and Po is a variable. Therefore, this definition option performs an interpolation between two linear functions of two boundaries.
To define a property or variable by using interpolation
1
In the property browser, click the property or variable that you want to define or edit.
2
In the Variable type box, select Interpolate Property.
3
To define Ptop, the variable representing the top boundary, do one of the following:
4
User Guide
•
To assign a constant, click Constant, and then type a numerical constant in the box.
•
To set Ptop to equal another variable in the model, click Variable, and then select the variable in the box.
To define Ztop, the Z value of the top boundary, do one of the following:
•
To assign a constant, click Constant, and then type a numerical constant in the box.
•
To set Ztop to equal the Z of another surface/layer, click Variable, and then select the variable in the box.
4.3 Defining Layer Property Values Directly
4-11
5
6
7
4.3.4
To define Pbot, the variable at the origin of the bottom boundary, do one of the following:
•
To assign a constant, click Constant, and then type a numerical constant in the box.
•
To set Pbot to equal another variable in the model, click Variable, and then select the variable in the box.
To define Zbot, the Z value of the bottom boundary, do one of the following:
•
To assign a constant, click Constant, and then type a numerical constant in the box.
•
To set Zbot to equal the Z of another surface/layer, click Variable, and then select the variable in the box.
Click Update Variable Definition to apply your changes.
Defining Properties or Variables from Grid Properties This definition option creates a variable whose value at a given point in the selected layer is defined by the value of a Voxet property at the same (X,Y,Z) position. The name of the Voxet property need not be the same as the name of the variable or the layer property that you are defining. To use this definition option, you need a Voxet with the desired property. Ideally, choose a Voxet that has the same or greater spatial extent as your model in order to avoid a possible core dump.
To define a property or variable from a grid property
4-12
1
In the property browser, click the property or variable that you want to define or edit.
2
In the Variable type box, select From Grid Property.
3
In the Voxet box, enter the name of the Voxet that includes the property you want.
4
In the Property box, enter the name of the property.
5
If you want to extrapolate the property outside the Voxet, select the Extrapolate check box.
6
If you want to set the point where the values are not defined as the specified default value, select the Use the default value check box, and then type a number in the box.
7
Click Update Variable Definition to apply your changes.
Defining Property Values for Velocity Models
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
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4.3.5
Defining Values from Surface or Layer Boundary Properties For information, see:
• • •
"Defining Values from Surface Boundaries," page 4-13 "Defining Values from Layer Boundaries," page 4-14 "Notes on Defining Values from Surfaces and Layers," page 4-18
This definition option creates a variable whose value at a point (x, y, z) is determined by a property value on the selected boundary at the same xy-position. The boundary can be either a Surface or a layer. In other words, the command does the following:
•
Shoots from a point (x, y, z) inside the layer of the model directly upward or downward until it hits the selected source boundary.
•
Sets the property value at that impact point as the value of the variable at the shooting point (x, y, z).
Defining Values from Surface Boundaries Figure 4–3 on page 4-7 illustrates the parameters used in this definition option, and Figure 4–6 on page 4-14 presents graphic examples of where impact points may be located. These figures may help you better understand the roles of theses parameters. To use this definition option, your model should include a Surface with the desired property. The name of the Surface property need not be the same as the variable or the layer property. Ideally, choose a Surface that has the same or greater spatial extent in the X and Y directions as the layer. If some points in the layer have no impact point (as shown in Figure 4–4 on page 4-8, right side), the following may happen:
•
If the variable is an intermediate variable (to be used in a property function), you may run into problems.
•
If the variable is being defined as the property, there will be a no-data value at those points without an impact point, which is acceptable.
Vertical location is important as well. If the shoot direction is purely upward, for example, the Surface should exist above all points of the layer in order to find an impact point for every point in the selected layer.
User Guide
4.3 Defining Layer Property Values Directly
4-13
Figure 4–6 Finding a property value on the source Surface for a given point in the model layer
Not the source Surface
Layer
Source surface
two_way=on, from_inside=on Not the source Surface
Layer
Source surface
Z=-1, two_way=off, from_inside=on
Not the source Surface
Layer
Source surface
Z=-1, two_way=off, from_inside=off Not the source Surface
Layer
Source surface
Z=+1, two_way=off, from_inside=on
Defining Values from Layer Boundaries A source Surface is any Surface that:
• •
Serves as a bounding Surface of the specified layer Lies in the path of a shooting ray
Figure 4–7 presents graphic examples of where impact points may be located.
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Figure 4–7 Finding a property value on the bounding Surfaces of the source layer for a given point in the model layer
A source Surface
A source Surface
Source layer & Model layer
X
Source layer & Model layer
X
X X
X A source Surface
A source Surface
X two_way=on, from_inside=on
Z=-1, two_way=off, from_inside=off A source Surface
A source Surface
Source layer & Model layer
Source layer & Model layer
X
X X A source Surface
X
A source Surface X X
Z=-1, two_way=off, from_inside=on
Z=+1, two_way=off, from_inside=on
This definition option can be useful when there is more than one top and/or more than one bottom bounding Surface for the layer of interest. This definition option ensures that at any given point in the selected layer, the variable will find a Value (an impact point), since a layer, by definition, is completely bounded. (There is one exception: when part of the bounding surface of the given layer is the bounding box of the model, the command may not be able to locate an impact point.)
User Guide
4.3 Defining Layer Property Values Directly
4-15
To define a property or variable from a surface or layer boundary
1
In the property browser, click the property or variable that you want to define or edit.
2
In the Variable type box, select From Surface or Layer Boundary Property.
3
Do one of the following:
•
To calculate a variable from a layer boundary, skip to step 6.
•
To calculate a variable from a surface boundary, click Surface.
4
In the Surface box, enter the name of the Surface that includes the property you want.
5
In the Surface property box, enter the name of the property on the selected Surface. (This does not have to be the same name as the name of the variable or the name of the layer property.) Skip to step 9.
6
Click Layer.
7
In the Layer box, enter the name of the Source (target) layer whose bounding Surfaces will be the source Surfaces. Important Ensure that the property you want is defined on all of those Surfaces.
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8
In the Property box, enter the name of the property on the bounding Surfaces of the selected source layer (This does not have to be the same name as the name of the variable or the name of the layer property.)
9
If you want to search for impact points in only one shoot direction, do one of the following:
•
To search upward, select 1 in the Z coordinate of projection vector box. (See "dir_Z = +1" on page 4-6.)
•
To search downward, select -1 in the Z coordinate of projection vector box. (See "dir_Z = -1" on page 4-6.)
10 If you want to ignore the dir_z parameter and to search for impact points in both shoot directions, select the Two-way projection check box. (See "two_way" on page 4-6 and Figure 4–3 on page 4-7.) Important When searching two ways, you can only shoot from inside Be sure to also select the Offset from boundary check box in step 11. 11 If you want to shoot from inside, select the Offset from boundary check box. To shoot from outside, clear the check box. (See "Shoot Position" on page 4-7 and Figure 4–3 on page 4-7.) 12 If you want to set the point where the values are not defined as the specified default value, select the Use the default value check box, and then type a number in the box. 13 Click Update Variable Definition to apply your changes.
User Guide
4.3 Defining Layer Property Values Directly
4-17
Notes on Defining Values from Surfaces and Layers •
Figure 4–8 Model types and impact points
In a Model3d, SKUA and GOCAD recognize not only which objects form the bounding Surface of a layer, but also which portion of the objects really form the boundaries. In a Voxet Model, however, SKUA and GOCAD only recognize whole Surfaces, not the separate portions. You need to ensure that your specifications will direct SKUA or GOCAD to find the proper impact points. This important concept is illustrated in Figure 4–8.
S1
X
X
S1
pA dir_Z = -1 from_inside = off Model3d
L1 (a)
L1 (b)
S2
pA dir_Z = -1 from_inside = off Model3d
X
X
S2
4-18
pA dir_Z = -1 from_inside = off Voxet Model
pB
pA
L2 (c)
dir_Z = -1 from_inside = off Voxet Model
pB L2 (d)
•
Given the same shoot specifications (Z+ from outside, target layer Surface L1) and geology, the two types of models may produce different impact points for a given point in a layer. This is because a Model3d recognizes different portions of an object, while a Voxet Model does not.
•
In Figure 4–8 (a), Only the lower portion of the closed Surface S1 is recognized as part of the bounding Surface of the layer L1; therefore, the first intersection with S1 is ignored and the second one is chosen as the impact point.
•
In Figure 4–8 (b), S1 is recognized as a whole as part of the bounding Surface of the layer L1, and therefore the first intersection with S1 is chosen as the impact point.
•
In Figure 4–8 (c) and (d), the two models produce the same impact point for point A (pA), because the from_outside shooting point is lower. (The shooting point only needs to be higher than any point in the layer L1.) At point B (pB), however, the two models will again produce different impact points.
Defining Property Values for Velocity Models
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4.4
Defining Properties or Variables by Using Property Functions You can use these definition options to create property functions of varying complexity. Add Functions:
• • • • • • • • • •
Undefined Build In Constant Linear Function (For information, see "Defining Properties or Variables by Using Linear Functions" on page 4-20.) Exponential Function Script (For information, see "Defining Property Functions by Using Scripts" on page 4-23.) Linear Function of Property Interpolated Property From Grid Property From Surface or Layer Boundary Property
Linear functions: Linear functions have the following form:
P p = P o p + K p Z p – Zo p If you use user-defined variables in a linear function, define the variables (see "Working with the Variable Type Menu" on page 4-4) after you define the function itself. Exponential functions: Exponential functions have the following form: K Z p – Zo p P p = Po p Scripts: Script syntax is similar to the awk or C programming language. If you use user-defined variables in a script function, you can define the variables (see "Working with the Variable Type Menu" on page 4-4) either before or after you define the function itself. For information, see:
• • •
User Guide
"Defining Properties or Variables by Using Linear Functions," page 4-20 "Defining Properties or Variables by Using Exponential Functions," page 4-22 "Defining Property Functions by Using Scripts," page 4-23
4.4 Defining Properties or Variables by Using Property Functions
4-19
4.4.1
Defining Properties or Variables by Using Linear Functions Use this definition option to define the layer property as either
•
A simple linear function of Z (the Z coordinate of the given (x, y, z) point)
P x y z = Po + K Z – Z o Where P(x, y, z) is the linear property function, Z is the Z coordinate of the given (x, y, z) point, and P o, K, and Z o are constants.
•
A complex linear function:
P x y z = Po x y z + K x y z Z – Z o x y z where P(x, y, z) is the linear property function, Z is the Z coordinate of a given point, and Po, K and Z o are variables that you can define using one of the definition options found in "Working with the Variable Type Menu" on page 4-4.
To define a value by using a linear function
1
In the property browser, click the property or variable that you want to define or edit.
2
In the Variable type box, select Linear Function.
3
To define P0 (as in P(X, Y, Z) = P0+ K * (Z -Z0)), do one of the following:
4
5
4-20
•
To assign a constant, click Constant, and then type a numerical constant in the box.
•
To set P0 to equal another variable in the model, click Variable, and then select the variable in the box.
To define K (as in P(X, Y, Z) = P0+ K * (Z -Z0)), do one of the following:
•
To assign a constant, click Constant, and then type a numerical constant in the box.
•
To set K to equal another variable in the model, click Variable, and then select the variable in the box.
To define Z0 (as in P(X, Y, Z) = P0+ K * (Z -Z0)), do one of the following:
•
To assign a constant, click Constant, and then type a numerical constant in the box.
•
To set Z0 to equal another variable in the model, click Variable, and then select the variable in the box.
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6
To make Z positive upward, select the Z is positive upward check box. To make Z positive downward, clear the check box.
7
User Guide
Click Update Variable Definition to apply your changes.
4.4 Defining Properties or Variables by Using Property Functions
4-21
4.4.2
Defining Properties or Variables by Using Exponential Functions Use this definition option to define the layer property as either
•
A simple linear function of Z (the z-coordinate of the given (x,y,z) point)
P(x,y,z ) = P0 * exp [K * (Z -Z0 )] Where: P (x,y,z) is the linear property function, Z is the z-coordinate of the given (x,y,z) point, and P 0, K, and Z 0 are constants.
•
A complex linear function
P(x,y,z ) = P0 (x,y,z) + K(x,y,z) * (Z - Z0 (x,y,z)) Where: P(x,y,z) is the linear property function, Z is the z-coordinate of a given point, and P 0, K, and Z 0 are variables that you can define using one of the definition options found in "Working with the Variable Type Menu" on page 4-4.
To define a value by using an exponential function
1
In the property browser, click the property or variable that you want to define or edit.
2
In the Variable type box, select Exponential Function.
3
To define P0 (as in P(X, Y, Z) = P0+ K * (Z -Z0)), do one of the following:
4
5
6
4-22
•
To assign a constant, click Constant, and then type a numerical constant in the box.
•
To set P0 to equal another variable in the model, click Variable, and then select the variable in the box.
To define K (as in P(X, Y, Z) = P0+ K * (Z -Z0)), do one of the following:
•
To assign a constant, click Constant, and then type a numerical constant in the box.
•
To set K to equal another variable in the model, click Variable, and then select the variable in the box.
To define Z0 (as in P(X, Y, Z) = P0+ K * (Z -Z0)), do one of the following:
•
To assign a constant, click Constant, and then type a numerical constant in the box.
•
To set Z0 to equal another variable in the model, click Variable, and then select the variable in the box.
To make Z positive upward, select the Z is positive upward check box.
Defining Property Values for Velocity Models
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
To make Z positive downward, clear the check box. 7
4.4.3
Click Update Variable Definition to apply your changes.
Defining Property Functions by Using Scripts • •
"About Script Property Functions," page 4-23 "Creating Script Property Functions," page 4-24
About Script Property Functions Use this definition option to create sophisticated property functions. You need at least minimal knowledge of the awk or C programming languages to take full advantage of this powerful tool. All variables used in a property script (except the three built-in variables, X, Y, and Z) should be defined as variables for the layer property by using the definition options found in "Working with the Variable Type Menu" on page 4-4. The name of another property (or the name of a variable in another property) in the selected layer (or any other layer) is not recognized as a pre-defined variable for a property script. If you want to use another property (or a variable in another property) as a variable in the current property script, you need to define a new variable for the current property, giving the new variable the same definition as the other property (or the variable in the other property).
Script syntax
The syntax used to define a script property function is similar to the C programming language. All script functions should be enclosed in { }. All operations should end with ";" and be enclosed in { }. You can include the following components in your script:
• • • •
numbers the variables X, Y, and Z Variables that you have defined for a specific layer property logical expressions such as &&, ||, ==, !, =, if, else,
•
the following 11 pre-defined functions:
• • • • • • • • • • •
User Guide
sqrt (x) = the square root of x exp(x) = e x log(x) = ln(x) log10(x) = log10 (x) cell (x) = the closest integer that is greater than or equal to x floor (x) = the closest integer that is less than or equal to x fabs (x) = the absolute value of (x) pow (x, y) = xy cos (x) = Cosine (x) sin (x) = Sine (x) tan (x) = Tangent (x)
4.4 Defining Properties or Variables by Using Property Functions
4-23
Examples of script functions
• • •
{ if (PERM>0.3) {OIL=PORO*(1-WATER);} else {OIL = 0;} } { if (PORO With Property Model to open the dialog box.
•
Surface, Voxet, or SGrid commands > Model3d or Model (as applicable) > Paint Voxet to open the dialog box.
3
In the Model box, enter the model that contains the property function.
4
In the Property box, enter the property that you want to review.
5
In the Layer name box, select the layer to which the property function is attached.
6
In the Voxet voxet box, select the Voxet onto which you want to paint the selected model property.
7
In the Voxet Property box, select the name of the property that you want to paint over. Note The selected property will be painted over by values derived from the property function in the model.
User Guide
4.5 Visualizing Property Functions
4-25
4.5.2
Painting a Velocity Function on a Grid You can use the Block Velocity Functions on Grid command to "paint" a velocity function on a grid so that you can visualize the velocity function velocities. The grid should have the same or greater spatial extent as the velocity function. You can paint the velocity function with different velocity types.
To paint a velocity function on a grid
1
Select Velocity commands > Velocity Modeling > Block Velocity Functions on Grid to open the Block Velocity Function on Grid dialog box.
2
In the Grid box, select the grid on which you want to paint the velocity function.
3
In the Velocity function box, select the velocity function that you want to paint.
4
In the Velocity box, select the velocity property of the velocity function.
5
In the Output type box, select the velocity type that you want to paint on the grid.
6
In the Output velocity box, enter the name of the new velocity property that you want to paint on the grid.
7
For Input velocity function interpolation, select of the following methods for interpolating between velocity data points.
8
4-26
•
linear. The velocity is linearly interpolated from the two values on either side of it.
•
constant. The velocity is constant within an interval.
Click OK or Apply.
Defining Property Values for Velocity Models
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
4.6
Adding Properties to Velocity Models Use this function to create global properties for velocity models. You can also designate a property type for each property. You use property types to group universal statistical parameters so that all the properties that you define as being in the same property type are in the same statistical pool. For example, you may have three different type of permeability measurements: one from core samples, one from skin damage estimation and one from theoretical calculation. You could name them permc, perms and permt, respectively. If you assign all three to the same property type Perm, then the data points from all three properties will be included when you calculate the mean (or any other statistical measure) of the property type Perm.
To add a property to a velocity model
1
2
User Guide
To open the Create Property dialog box, do either of the following:
•
Select Surface, Voxet, or SGrid commands > Model3D or Model (as applicable) > Add Property.
•
From the Property Model Editor, click Add Property.
Specify the property options as described in Part IV: Foundation Modeling, "Creating an Object Property or Well Log" on page 12-3. If it is not already preselected, select Velocity as the Category.
4.6 Adding Properties to Velocity Models
4-27
4.7
Deleting Properties from Velocity Models For information, see Part IV: Foundation Modeling, "Copying, Deleting, and Renaming an Object Property" on page 12-6.
4-28
Defining Property Values for Velocity Models
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
5 Creating Grid Properties with Geostatistical Functions In this chapter
Overview
•
"Geostatistics System File Formats," page 5-2
•
"Estimating Grid Properties with Kriging Algorithms," page 5-6
•
"Running Geostatistical Simulations," page 5-18
In Paradigm™ SKUA ® and Paradigm™ GOCAD ® , you can apply geostatistical functions to grids (SGrid and Voxet objects). To do this, you should be familiar with geostatistical concepts and terminology and have the necessary background to run geostatistical applications. The geostatistical applications in SKUA and GOCAD use the geostatistical software library, GSLIB, from Stanford University (for information, see GSLIB:
Geostatistical Software Library and User's Guide, C.V. Deutsch & A.G. Journel Oxford Press, 1992). For additional information about terms and methods, see Statistics for Engineers and Geoscientists, J.L. Jensen et al., Prentice Hall, 1996.
5-1
5.1
Geostatistics System File Formats The following sections describe additional files and formats needed for running some of the geostatistical commands.
• • • • • •
5.1.1
"GS File," page 5-2 "Column_Average_Map File," page 5-4 "Scattergram File," page 5-4 "External_Histogram File," page 5-5 "Facies_Map File," page 5-5 "Annealing_Schedule File," page 5-5
GS File • •
"Variogram and Associated Parameters File Format," page 5-2 "GS File Examples," page 5-3
Variogram and Associated Parameters File Format A GS file has the following parameters stored in the specified sequence: 1 COORDINATE_SYSTEM XYW 2 KRIGING_TYPE 1 3 MAX_CLOSE m 4 KRINGING_OPTION 1 5 SEARCH_ELLIPSOID S F T 6 COVARIANCE MODEL TNVar n 7 type1 1 1 1 S1 F1 T1 NVar1 . . . . . typen n n n Sn Fn Tn NVarn . END n+5 n+6
These are user-specified parameters, which should be entered as shown.
Explanation of individual lines in a GS file
1
The coordinate system can be either xyz, xyw, or uvw.
2
This line is ignored, but it should be present as shown.
3
This line gives the maximum number of data points, m, that will be used to krige the property value at any given node. Only the closest m points are used.
4
This line specifies simple kriging (0) or ordinary kriging (1).
5
This line describes the search ellipsoid in the uvw- or xyz-coordinate system.
• • • • • •
5-2
is the angle with the first axis (u or x). is the angle with the second axis (v or y). is the angle with the third axis (w or z). S is the length of the search radius ellipsoid along the first axis. F is the length of the search radius ellipsoid along the second axis. T is the length of the search radius ellipsoid along the third axis.
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
6
This line describes the variogram model.
• • 7
TNVar is the sill (total variance) of the variogram model. n is the number of nested components of the variogram model.
This line describes the first component of the nested variogram model.
•
type1 is the type of theoretical variogram used in the component. It should be one of the following (in upper case): SPHERICAL, GAUSSIAN, EXPONENTIAL, or POWER.
•
n n n Sn Fn Tn are the parameters of the variogram ellipsoid, similar to those at line 5.
•
NVar1 is the variance contribution of the first component.
•
The rest of the files describe the rest of the components in the variogram model.
•
The last line should be as shown.
GS File Examples Below are examples (with comments) of two types of variogram files:
• • Indicator simulation example
User Guide
"Indicator simulation example" on page 5-3 "Gaussian simulation example" on page 5-4
# Comment lines start with this symbol # coordinate system can either be XYZ, XYW, or UVW # in this example, XYW is chosen; therefore, the areal correlation # ranges are in real-world coordinates and the vertical correlation # range is in normalized (0 to 1) coordinate COORDINATE_SYSTEM XYW # not used KRIGING_TYPE 0 # maximum number of nearby data for kriging MAX_CLOSE 16 # 0 = simple kriging; 1 = ordinary kriging KRIGING_OPTION 0 # 3 cutoffs NB_CUT_OFFS 3 # first cutoff is 0.268 with cumulative probability of 25% # second cutoff is 0.300 with cumulative probability of 50% # third cutoff is 0.332 with cumulative probability of 75% CUT_OFFS 0.268 0.25 0.300 0.50 0.332 0.75 # search ellipsoids corresponding to each cutoff # format: angle1 angle2 angle3 range1 range2 range3 SEARCH_ELLIPSOID 45. 0. 0. 5000. 2500. 0.2 SEARCH_ELLIPSOID 0. 0. 0. 5000. 5000. 0.2 SEARCH_ELLIPSOID 135. 0. 0. 5000. 2500. 0.2 # covariance model for each cutoff # format COVARIANCE_MODEL sill number_of_nested_structures # model_type angle1 angle2 angle3 range1 range2 range3 contribution # model type can either be SPHERICAL EXPONENTIAL GAUSSIAN or POWER # in this example, there is only 1 nested structure, so only one model line # is needed # covariance for first cutoff COVARIANCE_MODEL 1. 1 SPHERICAL 45. 0. 0. 3000. 500. 0.1 1. # covariance for second cutoff COVARIANCE_MODEL 1. 1 SPHERICAL 0. 0. 0. 2500. 2500. 0.1 1. # covariance for third cutoff
5.1 Geostatistics System File Formats
5-3
COVARIANCE_MODEL 1. 1 SPHERICAL 135. 0. 0. 3000. END
Gaussian simulation example
5.1.2
250.
0.1
1.
# coordinate system can either be XYZ, XYW, or UVW # in this example, XYW is chosen; therefore, the areal correlation # ranges are in real-world coordinates and the vertical correlation # range is in normalized (0 to 1) coordinate COORDINATE_SYSTEM XYW # not used KRIGING_TYPE 0 # maximum number of nearby data for kriging MAX_CLOSE 16 # 0 = simple kriging; 1 = ordinary kriging KRIGING_OPTION 0 # search ellipsoid # generally, one should make the ranges of the search ellipsoid # larger than the correlation ranges # format: angle1 angle2 angle3 range1 range2 range3 SEARCH_ELLIPSOID 0. 0. 0. 4000. 4000. 0.4 # covariance model # format COVARIANCE_MODEL sill number_of_nested_structures # model_type angle1 angle2 angle3 range1 range2 range3 contribution # model type can either be SPHERICAL EXPONENTIAL GAUSSIAN or POWER # in this example, there is only one nested structure, so only one model line # is needed COVARIANCE_MODEL 1. 1 SPHERICAL 0. 0. 0. 2000 2000 0.2 1. END
Column_Average_Map File This file is needed for block kriging and simulated annealing (see "Running Annealing Simulations" on page 5-26). This example uses an SGrid with the dimensions 138x33x100. The first two lines should start with NX and NY, which specify the number of cells in the u and v directions, followed by NX*NY lines of data (one data per line) that represent the column averages. NX NY 0.23 ... 0.30
5.1.3
138 33
Scattergram File This file is needed for cloud transformations with P-fields (see "Running Cloud Transform Simulations with P-Fields" on page 5-29). This file has no header lines, just two columns of data. Independent_VariableDependent_Variable 0.1 1.5 0.1 1.3 0.1 1.6 ... 1.2 3.9
5-4
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
5.1.4
External_Histogram File This file is needed for simulated annealing (see "Running Annealing Simulations" on page 5-26) and continuous histogram correction (see "Performing Continuous Histogram Corrections" on page 5-32). This file has no header lines, just a column of data. Data_Value
The command then constructs the histogram using the data read in from the file. 1.0 0.9 ... 1.2
5.1.5
Facies_Map File This file is needed for Fill From Facies Map (see "Filling Grids with Facies Map Data" on page 5-34). This file has a header line for user identification (not used in the algorithm), followed by a series of data lines in the following format: X_coord 1230303.0 ... 3030303.0
5.1.6
Y_coord 39393939.0
Facies_value 1
10393030.0
3
Annealing_Schedule File This file is needed in Simulated Annealing (see "Running Annealing Simulations" on page 5-26). # Comment lines start with this symbol #but there are no real comments because if the variables #are not obvious, it will take too long to define them # comments INITIAL_TEMPERATURE 0.001 REDUCTION_FACTOR 0.1 # controls how temperature is lowered, 0 Kriging to open the Kriging dialog box.
3
In the Grid Object box, enter one or more Voxets or SGrids.
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
4
In the Region name box, enter the grid object region where the kriging will be performed. Note By default, kriging will be performed for all points (everywhere) on the grid.
5
In the Discrete property server by box, enter the object that carries the existing property values.
6
In the By region box, enter the input data region.
7
In the Property box, select the object property to be used in the operation.
8
In the New property prefix box, type the prefix for the created properties. (For example, if you type Kriging_, the two new created properties will be named Kriging_estimate and Kriging_variance.)
9
To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either of these:
•
Enter the path to the file in the GS file box.
•
Click
, find and select the file, and then click OK.
10 If you want to set options for the variogram and associated parameters, click Advanced to expand the dialog box.
a
In the Kriging Type box, select one the following kriging options:
• • • b
Simple. Residuals are computed from the mean of the data and kriged. Ordinary. Input data values are used directly for the kriging. Use_variogram_file_setting. Use the type set in the variogram file.
To allow for the possibility that the result at a cell containing data points is not kriged, but rather directly assigned from input data in that cell, select one of the following data value assignment options:
•
No data assignment. All cells are kriged.
•
Assign data to nearest cells. In any particular cell, the data point closest to the cell center is assigned as the estimation at the cell.
•
Assign mean at cell center. The mean of all the data points in a particular cell is assigned as the cell value. If you choose this option, also select a method of computing the mean in the Mean computation type box, and type the value for the exponent (in the standard mean power equation) in the Power mean power box.
11 Click OK or Apply.
User Guide
5.2 Estimating Grid Properties with Kriging Algorithms
5-7
5.2.2
Estimating Properties with Kriging with Trend In kriging with trend (also known as universal kriging), the modeled property is assumed to follow a trend that is only a function of the location coordinates. You should have an ASCII file containing the variogram data and an object that can serve as the property source (it should lie at least partially inside the SGrid or Voxet).
To run kriging with trend to create SGrid or Voxet Properties
1
Display the SGrid or Voxet and the property object in the 3D Viewer.
2
Select Voxet, SGrid, or General commands > Geostatistics > Kriging with Trend to open the Kriging With Trend dialog box.
3
In the Grid Object box, enter one or more Voxets or SGrids.
4
In the Region name box, enter the grid object region in which the kriging will be performed. Note By default, kriging will be performed for all points (everywhere) on the grid.
5-8
5
In the Discrete property server by box, enter the object that carries the existing property values.
6
In the By region box, enter the input data region.
7
In the Property box, select the object property to be used in the operation.
8
In the New property prefix box, type the prefix for the created properties. (For example, if you type Kriging_, the two new created properties will be named Kriging_estimate and Kriging_variance.)
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
9
To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either:
•
In the GS file box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
10 In the Kriging Type box, select one the following kriging options:
• • •
Simple. Residuals are computed from the mean of the data and kriged. Ordinary. Input data values are used directly for the kriging. Use_variogram_file_setting. Use the type set in the variogram file.
11 To allow for the possibility that the result at a cell containing data points is not kriged, but rather directly assigned from input data in that cell, do one of the following to assign data values to cells:
•
Select the Assign data to nearest cells check box. In any particular cell, the data point closest to the cell center is assigned as the estimation at the cell.
•
Clear the Assign data to nearest cells check box. All cells are kriged.
12 In the Trend Model area, select the check boxes representing the trend components you want.
•
a, u, a5v2, or a9vw. The trend is a function of a, u+a5v2+a9vw.
•
a, a5, or a9. These are unknown weights that will be estimated during the kriging process.
13 Click OK or Apply.
User Guide
5.2 Estimating Grid Properties with Kriging Algorithms
5-9
5.2.3
Estimating Properties with Kriging with External Drift In kriging with external drift, the trend is a linear function of a secondary property (drift) that does not have to be in the same units as the data. You should have an ASCII file containing the variogram data and an object that can serve as the property source (it should lie at least partially inside the SGrid or Voxet).
To run kriging with external drift to create SGrid or Voxet properties
1
Display the SGrid or Voxet and the property object in the 3D Viewer.
2
Select Voxet, SGrid, or General commands > Geostatistics > Kriging with External Drift to open the Kriging With External Drift dialog box.
3
In the Grid Object box, enter one or more Voxets or SGrids.
4
In the Region name box, enter the grid object region in which the kriging will be performed. Note By default, kriging will be performed for all points (everywhere) on the grid.
5-10
5
In the Discrete property server by box, enter the object that carries the existing property values.
6
In the By region box, enter the input data region.
7
In the Property box, select the object property to be used in the operation.
8
In the Drift Property box, enter the secondary property that exists everywhere on the Grid.
9
In the New property prefix box, type the prefix for the created properties. (For example, if you type Kriging_, the two new created properties will be named Kriging_estimate and Kriging_variance.)
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
10 To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either:
•
In the GS file box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
11 In the Kriging Type box, select one the following kriging options:
• • •
Simple. Residuals are computed from the mean of the data and kriged. Ordinary. Input data values are used directly for the kriging. Use_variogram_file_setting. Use the type set in the variogram file.
12 To allow for the possibility that the result at a cell containing data points is not kriged, but rather directly assigned from input data in that cell, do one of the following to assign data values to cells:
•
Select the Assign data to nearest cells check box. In any particular cell, the data point closest to the cell center is assigned as the estimation at the cell.
•
Clear the Assign data to nearest cells check box. All cells are kriged.
13 Click OK or Apply.
User Guide
5.2 Estimating Grid Properties with Kriging Algorithms
5-11
5.2.4
Estimating Properties with Bayesian Kriging Bayesian kriging is similar to "Estimating Properties with Kriging with External Drift" on page 5-10, except that the drift property should be in the units of the data being estimated. You need an ASCII file containing the variogram data and an object that can serve as the property source (it should lie at least partially inside the SGrid or Voxet).
To run Bayesian kriging to create SGrid or Voxet properties
1
Display the SGrid or Voxet and the property object in the 3D Viewer.
2
Select Voxet, SGrid, or General commands > Geostatistics > Bayesian Kriging to open the Bayesian Kriging dialog box.
3
In the Grid Object box, enter one or more Voxets or SGrids.
4
In the Region name box, enter the grid object region in which the kriging will be performed. Note By default, kriging will be performed for all points (everywhere) on the grid.
5-12
5
In the Discrete property server by box, enter the object that carries the existing property values.
6
In the By region box, enter the input data region.
7
In the Property box, select the object property to be used in the operation.
8
In the Guess Property box, enter the secondary property that exists everywhere on the Grid and has the same units as the property being estimated (selected in step 7).
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
9
In the New property prefix box, type the prefix for the created properties. (For example, if you type Kriging_, the two new created properties will be named Kriging_estimate and Kriging_variance.)
10 To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either:
•
In the GS file box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
11 In the Kriging Type box, select one the following kriging options:
• • •
Simple. Residuals are computed from the mean of the data and kriged. Ordinary. Input data values are used directly for the kriging. Use_variogram_file_setting. Use the type set in the variogram file.
12 To allow for the possibility that the result at a cell containing data points is not kriged, but rather directly assigned from input data in that cell, select one of the following data value assignment options:
•
No data assignment. All cells are kriged.
•
Assign data to nearest cells. In any particular cell, the data point closest to the cell center is assigned as the estimation at the cell.
•
Assign mean at cell center. The mean of all the data points in a particular cell is assigned as the cell value. If you choose this option, also select a method of computing the mean in the Mean computation type box, and type the value for the exponent (in the standard mean power equation) in the Power mean power box.
13 Click OK or Apply.
User Guide
5.2 Estimating Grid Properties with Kriging Algorithms
5-13
5.2.5
Estimating Properties with Collocated Cokriging Use collocated cokriging to fill the selected SGrid or Voxet with property values (to assign property values to all the nodes in the SGrid or Voxet). You need an ASCII file containing the variogram data and an object that can serve as the property source (it should lie at least partially inside the SGrid or Voxet). The SGrid or Voxet should have a property that will be used as the soft data (see step 9).
To run collocated cokriging to create SGrid or Voxet properties
1
Display the SGrid or Voxet and the property source object in the 3D Viewer.
2
Select Voxet, SGrid, or General commands > Geostatistics > Collocated Cokriging to open the Collocated Cokriging dialog box.
3
In the Grid Object box, enter one or more Voxets or SGrids.
4
In the Region name box, enter the grid object region in which the kriging will be performed. Note By default, kriging will be performed for all points (everywhere) on the grid.
5-14
5
In the Discrete property server by box, enter the object that carries the existing property values.
6
In the By region box, enter the input data region.
7
In the Property box, select the object property to be used as the source for kriging. This property is considered the hard data.
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
8
In the New property prefix box, type the prefix for the created properties. (For example, if you type Kriging_, the two new created properties will be named Kriging_estimate and Kriging_variance.)
9
In the Soft data box, enter the name of the SGrid or Voxet property that will be used as the soft data in the cokriging.
10 In the Correlation coefficient box, type a positive number between 0 and 1, specifying the scale factor of the variogram data for the soft data. 11 To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either:
•
In the GS file box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
Note The variogram is used by the hard data, then scaled by the factor specified in step 10 on page 5-15 and used by the soft data. If the file is not in the default directory, you need to include the proper path in the file name.
12 To allow for the possibility that the result at a cell containing data points is not kriged, but rather directly assigned from input data in that cell, select one of the following data value assignment options:
•
No data assignment. All cells are kriged.
•
Assign data to nearest cells. In any particular cell, the data point closest to the cell center is assigned as the estimation at the cell.
•
Assign mean at cell center. The mean of all the data points in a particular cell is assigned as the cell value. If you choose this option, also select a method of computing the mean in the Mean computation type box, and type the value for the exponent (in the standard mean power equation) in the Power mean power box.
13 Click OK or Apply.
User Guide
5.2 Estimating Grid Properties with Kriging Algorithms
5-15
5.2.6
Estimating Properties with Indicator Kriging Use indicator kriging to fill the selected SGrid or Voxet with property values (to assign property values to all the Nodes in the SGrid or Voxet). You need an ASCII file containing the variogram data and an object that can serve as the property source (it should lie at least partially inside the SGrid or Voxet).
To run indicator kriging to create SGrid or Voxet properties
1
Display the SGrid or Voxet and the property source object in the 3D Viewer. Display a SGrid or Voxet Section with the property on which you want to run kriging.
2
Select Voxet, SGrid, or General commands > Geostatistics > Indicator Kriging to open the Indicator kriging dialog box.
3
In the Grid Object box, enter one or more Voxets or SGrids.
4
In the Region name box, enter the grid object region in which the kriging will be performed. Note By default, kriging will be performed for all points (everywhere) on the grid.
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5
In the Discrete property server by box, enter the object whose property will be the source for kriging.
6
In the By region box, enter the input data region.
7
In the Property box, select the object property to be used as the source for kriging.
8
In the New property prefix box, type the prefix for the created properties. (For example, if you type CutOff_, the two new created properties will be named CutOff_1, CuttOff_2, and so on.) The number of properties is equal to the number of cutoffs specified in the variogram file.
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
9
To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either:
•
In the GS file box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
Note If the file is not in the default directory, you need to include the proper path in the file name.
10 In the Kriging Type box, select one the following kriging options:
• • •
Simple. Residuals are computed from the mean of the data and kriged. Ordinary. Input data values are used directly for the kriging. Use_variogram_file_setting. Use the type set in the variogram file.
11 In the Distribution Type box, select the type of distribution function to be used. Your selection determines how the cutoff value given in the variogram files are used to define the indicator kriging (IK) stages and how the input property values are interpreted in each stage.
•
PDF (Probability Density Function). In each threshold value kriging, a data point equal to that value is considered 1 and a data point not equal to that value is considered 0. For discrete properties only.
•
CDF (Cumulative Distribution function). In each interval kriging, a data point within that interval is considered 1 and a data point outside of that range is considered 0. For continuous and discrete properties.
12 To allow for the possibility that the result at a cell containing data points is not kriged, but rather directly assigned from input data in that cell, do one of the following to assign data values to cells:
•
Select the Assign data to nearest cells check box. In any particular cell, the data point closest to the cell center is assigned as the estimation at the cell.
•
Clear the Assign data to nearest cells check box. All cells are kriged.
13 Click OK or Apply.
User Guide
5.2 Estimating Grid Properties with Kriging Algorithms
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5.3
Running Geostatistical Simulations There are several types of geostatistical simulations offered in this menu:
• • • • • • • • •
"Running Sequential Gaussian Simulations (SGS)," page 5-18 "Running Non-Conditional Sequential Gaussian Simulations," page 5-21 "Running Collocated Cokriging Simulations," page 5-22 "Running Sequential Indicator Simulations (SIS)," page 5-24 "Running Annealing Simulations," page 5-26 "Running Cloud Transform Simulations with P-Fields," page 5-29 "Performing Categorical Histogram Corrections," page 5-31 "Performing Continuous Histogram Corrections," page 5-32 "Filling Grids with Facies Map Data," page 5-34
A simulation method is more sophisticated than a kriging process in that it enables you not only to specify statistical anisotropy in terms of variogram parameters (as kriging does), but also to model heterogeneity by adding a random factor.
5.3.1
Running Sequential Gaussian Simulations (SGS) You can perform sequential Gaussian simulations, based on the selected property source and user-provided variogram data, to fill the selected Voxet with property values (to assign property values to all the Nodes in the SGrid or Voxet). This function generates default property names to store the result of each realization. If the default name already exists, the result of the current realization will replace the existing values.The default names of the created properties are SGS_simulation_1, SGS_simulation_2,..., SGS_simulation_n; where n is the specified number of simulations run. You need an ASCII file containing the variogram data and an object that can serve as the property source (it should lie at least partially inside the SGrid or Voxet).
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Creating Grid Properties with Geostatistical Functions
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Part VI: Velocity Modeling
To run an SGS to create SGrid or Voxet properties
1
Select Voxet, SGrid, or General commands > Geostatistics > Sequential Gaussian Simulation (SGS) to open the Sequential Gaussian Simulation dialog box.
2
In the Grid Object box, enter one or more Voxets or SGrids.
3
In the Region name box, enter the region in which the simulation will be performed. Property values outside the selected region will not be altered. Note By default, the simulation will be performed for the entire grid object (everywhere).
4
In the Discrete property server by box, enter the object whose property will be the source for the simulation.
5
In the By region box, enter the input data region.
6
In the Property box, select the object property to be used as the source for the simulation.
7
If you want to use a user-specified histogram, do the following: a
Select the Use external histogram check box.
b
In the External histogram box, enter the distribution that you want to use.
c
To view the distribution or to create a new one, click Manager appears.
. The Distribution
Note By default, the input data histogram is used to transform the input and realizations into and out to a normal score space.
User Guide
8
In the New property prefix box, type the prefix for the created properties.
9
In the Min box, type the low-cut value of the simulation value range (enter a reasonable number).
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10 In the Max box, type the high-cut value of the simulation value range (enter a reasonable number). Tip Be conservative; each simulation can take a while, and each simulation creates a new property.
11 In the Number of realizations box, type a positive integer specifying the number of simulations to be performed. 12 In the Seed box, type any number. (It will be used to start the random number generation process.) 13 To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either:
•
In the GS file box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
Note If the file is not in the default directory, you need to include the proper path in the file name.
14 In the Kriging Type box, select one the following kriging options:
• •
Simple. Residuals are computed from the mean of the data and kriged. Ordinary. Input data values are used directly for the kriging.
15 To perform the simulation recursively, select the Multi-grid simulation check box. (For large grids, this speeds up the operation and produces realizations that are truer to the variogram.) 16 Click OK or Apply.
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Creating Grid Properties with Geostatistical Functions
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5.3.2
Running Non-Conditional Sequential Gaussian Simulations You can perform non-conditional sequential Gaussian simulations, based on user-provided histogram parameters and variogram data, to fill the selected SGrid or Voxet with property values (to assign property values to all the Nodes in the SGrid or Voxet). You should have an ASCII file containing the variogram data.
To run a nonconditional SGS to create SGrid or Voxet properties
1
Select Voxet, SGrid, or General commands > Geostatistics > Unconditional SGS to open the Non Conditional Simulation dialog box.
2
In the Grid Object box, enter one or more Voxets or SGrids.
3
In the Region name box, enter the region in which the simulation will be performed. Property values outside the selected region will not be altered. Note By default, the simulation will be performed for the entire grid object (everywhere).
User Guide
4
In the Property class box, type the name of a new property class. (Property classes are used to set up a set of universal statistical parameters so that all the properties that you define as being in the same property class will be in the same statistical pool. For example, you can share color maps and their minimum and maximum settings.)
5
In the New property prefix box, type the prefix for the created properties.
5.3 Running Geostatistical Simulations
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6
If you want to use a user-specified histogram, do the following: a
Select the Use distribution object check box.
b
In the Distribution object box, enter the distribution that you want to use.
c
To view the distribution or to create a new one, click Manager appears.
d
Skip to step 10.
. The Distribution
Note By default, the input data histogram is used to transform the input and realizations into and out to a normal score space.
7
In the Distribution Type box, select the type of distribution function to use:
• • • 8
9
Tip Be conservative; each simulation can take a while, and each simulation creates a new property.
Normal. The mean is 0, and the sigma is 1/3 of the constant. Log-normal. The logarithm of the Normal distribution. Uniform. The min is -constant, and the max is +constant.
If you selected Normal or Log-normal in step 7, do the following: a
type the Mean of the distribution function in the Mean box (enter a reasonable number).
b
In the Sigma box, type the standard deviation of the distribution function (enter a reasonable number).
If you selected Uniform in step 7, do the following: a
In the Min box, type the low-cut value of the simulation value range (enter a reasonable number).
b
In the Max box, type the high-cut value of the simulation value range (enter a reasonable number).
10 In the Number of realizations box, type a positive integer specifying the number of simulations to be performed. 11 In the Seed box, type any number. (It will be used to start the random number generation process.) 12 To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either:
•
In the GS file box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
13 Note If the file is not in the default directory, you need to include the proper path in the file name. 14 To perform the simulation recursively, select the Multi-grid simulation check box. (For large grids, this speeds up the operation and produces realizations that are truer to the variogram.) 15 Click OK or Apply.
5.3.3
Running Collocated Cokriging Simulations You can perform collocated cokriging simulations, based on the selected property source and user-provided variogram data, to fill the selected SGrid or Voxet with property values (to assign property values to all the Nodes in the SGrid or Voxet).
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Part VI: Velocity Modeling
You need an ASCII file containing the variogram data and an object that can serve as the property source (it should lie at least partially inside the SGrid or Voxet). The SGrid or Voxet should have a property that will be used as the soft data (see step 12).
To run collocated cokriging simulations to create SGrid or Voxet properties
1
Display the SGrid or Voxet and the property source object in the 3D Viewer.
2
Select Voxet, SGrid, or General commands > Geostatistics > Collocated Cokriging SGS to open the Collocated Cokriging Simulation dialog box.
3
In the Grid Object box, enter one or more Voxets or SGrids.
4
In the Region name box, enter the region in which the simulation will be performed. Property values outside the selected region will not be altered. Note By default, the simulation will be performed for the entire grid object (everywhere).
User Guide
5
In the Discrete property server by box, enter the object whose property will be the source for the simulation.
6
In the By region box, enter the input data region.
7
In the Property box, select the object property to be used as the source for the simulation.
8
If you want to use a user-specified histogram, do the following: a
Select the Use external histogram check box.
b
In the External histogram box, enter the distribution that you want to use.
5.3 Running Geostatistical Simulations
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c
To view the distribution or to create a new one, click Manager appears.
. The Distribution
Note By default, the input data histogram is used to transform the input and realizations into and out to a normal score space.
9
In the New property prefix box, type the prefix for the created properties.
10 In the Min box, type the low-cut value of the simulation value range (enter a reasonable number). 11 In the Max box, type the high-cut value of the simulation value range (enter a reasonable number). 12 To specify soft data information, do the following:
•
In the Soft data box, enter the name of the SGrid or Voxet property that will be used as the soft data in the cokriging.
•
Select the option indicating whether you want to use soft data from the entire grid or from the region only.
13 In the Correlation coefficient box, type a positive number between 0 and 1, specifying the scale factor of the variogram data for the soft data. Tip Be conservative; each simulation can take a while, and each simulation creates a new property.
14 In the Number of realizations box, type a positive integer specifying the number of simulations to be performed. Tip Be conservative; each simulation can take a while, and each simulation creates a new property.
15 In the Seed box, type any number. (It will be used to start the random number generation process.) 16 To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either:
•
In the GS file box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
Note The variogram is used by the hard data, then scaled by the factor specified in step 13 and used by the soft data. If the file is not in the default directory, you need to include the proper path in the file name.
17 To perform the simulation recursively, select the Multi-grid simulation check box. (For large grids, this speeds up the operation and produces realizations that are truer to the variogram.) 18 Click OK or Apply.
5.3.4
Running Sequential Indicator Simulations (SIS) You can perform sequential indicator simulations, based on the selected property source and user-provided variogram data, to fill the selected SGrid or Voxet with property values (to assign property values to all the Nodes in the SGrid or Voxet). You need an ASCII file containing the variogram data and an object that can serve as the property source (it should lie at least partially inside the SGrid or Voxet).
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Part VI: Velocity Modeling
To run an SIS to create SGrid or Voxet properties
1
Select Voxet, SGrid, or General commands > Geostatistics > Sequential Indicator Simulation (SIS) to open the Sequential Indicator Simulation dialog box.
2
In the Grid Object box, enter one or more Voxets or SGrids.
3
In the Region name box, enter the region in which the simulation will be performed. Property values outside the selected region will not be altered. Note By default, the simulation will be performed for the entire grid object (everywhere).
4
In the Discrete property server by box, enter the object whose property will be the source for the simulation.
5
In the By region box, enter the input data region.
6
In the Property box, select the object property to be used as the source for the simulation.
7
In the New property prefix box, type the prefix for the created properties.
8
In the Distribution Type box, select the type of distribution function to be used. Your selection determines how the cutoff value given in the variogram files are used to define the indicator kriging (IK) stages and how the input property values are interpreted in each stage.
•
User Guide
PDF (Probability Density Function). In each threshold value kriging, a data point equal to that value is considered 1 and a data point not equal to that value is considered 0. For discrete properties only.
5.3 Running Geostatistical Simulations
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•
9
CDF (Cumulative Distribution function). In each interval kriging, a data point within that interval is considered 1 and a data point outside of that range is considered 0. For continuous and discrete properties.
In the Min box, type the low-cut value of the simulation value range (enter a reasonable number).
10 In the Max box, type the high-cut value of the simulation value range (enter a reasonable number). Tip Be conservative; each simulation can take a while, and each simulation creates a new property.
11 In the Number of realizations box, type a positive integer specifying the number of simulations to be performed. 12 In the Seed box, type any number. (It will be used to start the random number generation process.) 13 To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either:
•
In the GS file box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
Note If the file is not in the default directory, you need to include the proper path in the file name.
14 To perform the simulation recursively, select the Multi-grid simulation check box. (For large grids, this speeds up the operation and produces realizations that are truer to the variogram.) 15 To allow for the possibility that the result at a cell containing data points is not kriged, but rather directly assigned from input data in that cell, select one of the following to assign data values to cells:
•
Assign most dominant value to cell. Computes the most dominant value in the cell, using all the volumes falling in that cell, and assigns that data value.
•
Assign nearest data to cell. Finds the closest value to the center of the cell and assigns that data value.
16 Click OK or Apply.
5.3.5
Running Annealing Simulations You can perform annealing simulations to populate the grid with property values. Original property data are carried by another object. You need the following to perform this function:
5-26
•
An SGrid or Voxet
•
An object that carries a discrete property (it should at least partially overlap the SGrid or Voxet spatially)
•
An ASCII file containing the variogram data
•
An annealing schedule file
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
To run an annealing simulation
1
Select Voxet, SGrid, or General commands > Geostatistics > Simulated Annealing to open the Annealing Simulation dialog box.
2
In the Grid Object box, enter one or more Voxets or SGrids.
3
In the Region name box, enter the region in which the simulation will be performed. Property values outside the selected region will not be altered. Note By default, the simulation will be performed for the entire grid object (everywhere).
User Guide
4
In the Discrete property server by box, enter the object whose property will be the source for the simulation.
5
In the By region box, enter the input data region.
6
In the Property box, select the object property to be used as the source for the simulation.
7
In the New property prefix box, type the prefix for the created properties.
8
In the Min box, type the low-cut value of the simulation value range (enter a reasonable number).
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9
In the Max box, type the high-cut value of the simulation value range (enter a reasonable number).
10 To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), do either:
•
In the GS file box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
Note If the file is not in the default directory, you need to include the proper path in the file name.
11 To specify the ASCII file that contains the annealing schedule (see "Annealing_Schedule File" on page 5-5), do either:
•
In the Schedule box, enter the path to the file.
•
Click to open the Select Text File dialog box, find and select the file, and then click OK.
12 In the Nlags box, type a positive integer specifying the number of variogram lags to be honored in the Annealing. (The default is 250.) 13 If you want to specify soft data information, do the following: a
Select the Honor correlation coefficient check box
b
In the Soft data box, enter the name of the SGrid or Voxet property that will be used as the soft data.
c
In the Correlation coefficient box, type the correlation coefficient between the property and the soft data.
14 If you want to specify the map containing column averages, do the following: a
Select the Honor column average map check box.
b
In the Map file box, enter the path to the map file (see "Column_Average_Map File" on page 5-4). Or, click to open the Select Text File dialog box, find and select the file, and then click OK.
15 If you want to use an external histogram stored in an ASCII file, do the following: a
Select the Honor external histogram check box.
b
In the Hist file box, enter the path to the file (see "External_Histogram File" on page 5-5). Or, click to open the Select Text File dialog box, find and select the file, and then click OK.
Tip Be conservative; each simulation can take a while, and each simulation creates a new property.
16 In the Number of realizations box, type a positive integer specifying the number of simulations to be performed. 17 In the Seed box, type any number. (It will be used to start the random number generation process.) 18 Click OK or Apply.
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5.3.6
Running Cloud Transform Simulations with P-Fields Performs cloud transform simulations in the selected region of an SGrid. You need a text file containing variogram information and a text file that contains the calibration (scattergram) information.
To run a cloud transform simulation
1
Select Voxet, SGrid, or General commands > Geostatistics > Cloud Transform (with P-Field) to open the Pfield Simulation dialog box.
2
In the Grid Object box, enter one or more Voxets or SGrids.
3
In the Region name box, enter the region in which the simulation will be performed. Property values outside the selected region will not be altered. Note By default, the simulation will be performed for the entire grid object (everywhere).
4
User Guide
In the Grid input property box, select the property to be used as the input data.
5.3 Running Geostatistical Simulations
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5
If you set an input property as a constraint on the cloud transform, select the Conditional pfield check box, and then do the following:
•
In the Discrete property server by box, enter the object that carries the conditioning data.
•
In the By region box, enter the input data region.
•
In the Property box, select the object property to be used as the conditioning data.
6
In the Property class box, type the name of a new property class. (Property classes are used to set up a set of universal statistical parameters so that all the properties that you define as being in the same property class will be in the same statistical pool. For example, you can share color maps and their minimum and maximum settings.)
7
In the New property prefix box, type the prefix for the created properties.
8
To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), in the GS file box, enter the path to the file. Or, click dialog box, find and select the file, and then click OK.
to open the Select Text File
Note If the file is not in the default directory, you need to include the proper path in the file name.
9
Select one of the following kriging options:
• •
Simple. Residuals are computed from the mean of the data and kriged. Ordinary. Input data values are used directly for the kriging.
10 To specify the ASCII file that contains the calibration data (see "Scattergram File" on page 5-4), in the Cloud file box, enter the path to the file. Or, click Select Text File dialog box, find and select the file, and then click OK.
to open the
11 In the Null data value in cloud file box, type the value used to represent null value in the scattergram. 12 In the Cloud transform binning box, select the type of binning to use in the cloud transform.
Tip Be conservative; each simulation can take a while, and each simulation creates a new property.
•
Number of bins. If you select this option, also type a positive integer specifying the fixed number of bins in the Num bins box.
•
Data points per bin. If you select this option, also type a positive integer specifying the fixed number of data points per bin in the Data per bin box.
•
Discrete Indep. Var. Indicators will be treated as discrete values.
13 In the Number of realizations box, type a positive integer specifying the number of simulations to be performed. (The default is 1.) Tip Be conservative; each simulation can take a while, and each simulation creates a new property.
14 In the Seed box, type any number. (It will be used to start the random number generation process. The default is 101.) 15 To perform the simulation recursively, select the Multi-grid simulation check box. (For large grids, this speeds up the operation and produces realizations that are truer to the variogram.) 16 Click OK or Apply.
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5.3.7
Performing Categorical Histogram Corrections You can transform an existing SIS PDF (categorical) realization to honor a user-specified PDF exactly. You need a text file containing variogram information and a property that contains the kriging variance information
To perform a categorical histogram correction
1
Select Voxet, SGrid, or General commands > Geostatistics > Categorical Histogram Correction to open the Categorical Histogram Correction dialog box.
2
In the Grid Object box, enter one or more Voxets or SGrids.
3
In the Region name box, enter the region in which the simulation will be performed. Property values outside the selected region will not be altered. Note By default, the simulation will be performed for the entire grid object (everywhere).
4
In the New property prefix box, type the prefix for the created properties.
5
In the Realization to be corrected box, select the property (realization) to be corrected.
6
If you want to specify how much the realization point can be modified, select the Use kriging Variance check box, and then select the variance in the Kriging variance box.
7
In the Seed box, type any number. (It will be used to start the random number generation process.)
8
To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), in the GS file box, enter the path to the file. Or, click dialog box, find and select the file, and then click OK.
to open the Select Text File
Note The PDF specified in this file is used to correct the input realization.
9
User Guide
Click OK or Apply.
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5.3.8
Performing Continuous Histogram Corrections You can condition the result of a simulation to fit an external histogram. The histogram can be an existing distribution, a single-column ASCII data file, or a property on an userspecified object. To perform this function, you need a text file containing variogram information and a property that contains the kriging variance information.
To perform a continuous histogram correction
1
Select Voxet, SGrid, or General commands > Geostatistics > Continuous Histogram Correction to open the Continuous Histogram Correction dialog box.
2
In the Grid Object box, enter one or more Voxets or SGrids.
3
In the Region name box, enter the region in which the simulation will be performed. Property values outside the selected region will not be altered. Note By default, the simulation will be performed for the entire grid object (everywhere).
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4
In the Realization to be corrected box, select the property (realization) to be corrected.
5
In the New property name box, type the name of the new grid object property that will store the result of the realization. (By creating a new property, you avoid modifying the input property.)
6
If you want to specify how much the realization point can be modified, select the Use kriging Variance check box, and then select the variance in the Kriging variance box.
7
If you want to use a histogram created from a property on an object, do the following:
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
8
9
•
In the Discrete property server by box, enter the object that will be used to construct the histogram.
•
In the By region box, enter the object region that will be used to build the histogram.
•
In the Property box, select the object property that will be used to build the histogram.
If you want to use an external histogram, do the following:
•
Click Histogram from parametric distribution.
•
In the External histogram box, enter the distribution that you want to use.
c
To view the distribution or to create a new one, click Manager appears.
. The Distribution
If you want to use a histogram stored in an ASCII file, do the following:
•
Click Histogram from ASCII file.
•
In the Hist file box, enter the path to the file (see "External_Histogram File" on page 5-5). Or, click to open the Select Text File dialog box, find and select the file, and then click OK.
10 fudging factor: A positive number (keyboard-entry), specifying how much the input realization can be changed. The larger the number, the more the input realization is allowed to change. Default=0.5. 11 x window size: The u-dimension of the search window used to find neighboring cells for calculating the average at any given cell. 12 y window size: The v-dimension of the search window used to find neighboring cells for calculating the average at any given cell. 13 z window size: The w-dimension of the search window used to find neighboring cells for calculating the average at any given cell. 14 Click OK or Apply.
User Guide
5.3 Running Geostatistical Simulations
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5.3.9
Filling Grids with Facies Map Data You can partially fill a grid with data from a facies map, then fill in the rest with property values generated by SIS. You need a text file containing variogram information and a text file that contains the facies map information.
To fill a grid with facies map data
1
Select Voxet, SGrid, or General commands > Geostatistics > Fill from Facies Maps to open the FaciesMap Simulation dialog box.
2
In the Grid Object box, enter one or more Voxets or SGrids.
3
In the Region name box, enter the region in which the simulation will be performed. Property values outside the selected region will not be altered. Note By default, the simulation will be performed for the entire grid object (everywhere).
5-34
4
In the New property prefix box, type the prefix for the created properties.
5
In the Discrete property server by box, enter the object that carries the existing property values.
6
In the By region box, enter the input data region.
7
In the Property box, select the object property to be used as the input data.
Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
8
In the Map file box, enter the path to the ASCII facies map file (see "Facies_Map File" on page 5-5). Or, click to open the Select Text File dialog box, find and select the file, and then click OK. Note The facies map contains X, Y and facies values in each line.
9
In the Map sampling rate box, type a positive number between 0 and 100, indicating the percentage of the SGrid region space that should be filled with a vertical projection of the facies map data. (The rest of the space will be filled with simulated values.)
10 To specify the ASCII file that contains the variogram data (see "GS File" on page 5-2), in the GS file box, enter the path to the file. Or, click dialog box, find and select the file, and then click OK.
to open the Select Text File
11 In the Map weight box, type a positive number between 0 and 100, specifying the weight percentage assigned to the map data. (The weight percentage of the property specified in step 7 will be 100 - the map weight.) 12 In the Well weight box, type a positive number between 0 and 100, specifying the weight percentage assigned to the well facies proportions. 13 In the Variogram file weight box, type a positive number between 0 and 100, specifying the weight percentage assigned to the variogram file facies proportions. 14 In the Seed box, type any number. (It will be used to start the random number generation process. The default is 101.) 15 Click OK or Apply.
User Guide
5.3 Running Geostatistical Simulations
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Creating Grid Properties with Geostatistical Functions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
6 Performing Velocity Conversions In this chapter
Overview
•
"Converting the Velocity Type in One Domain," page 6-2
•
"Converting the Velocity Type in Different Domains," page 6-3
•
"Converting the Velocity Type of Velocity Functions," page 6-5
The Velocity commands consist of a series of functions that perform velocity conversions and time-to-depth conversions (or depth-to-time conversions). Velocity can originate from different sources. The Velocity cube can be directly imported, computed from regional data within Paradigm™ SKUA ® and Paradigm™ GOCAD® using mathematical functions, or computed from field data (such as well logs, checkshots, stacking velocity, or VRMS) using geostatistical operations and/or interpolation methods. You can convert velocity from the following source types:
• •
Average, interval, RMS, or depth velocity (time domain) Average, interval, RMS, or time velocity (depth domain)
6-1
6.1
Converting the Velocity Type in One Domain Use this function to convert velocity within the same domain (time or depth). (For example, if the velocity is in time, the converted velocity should also be in time.) Note If you have a license that enables the use of multiple processors, you can take advantage of parallel processing for this command by ensuring that you enable the settings in Edit > Preferences > Multicore and GPU Processing. For more information, see Part I: Getting Started, "Setting Multicore and GPU Processing Preferences" on page 2-10.
To convert velocity in one domain
1
Select Velocity commands > Velocity Conversion > Voxet and Seismic Lines: In One Domain to open the Convert Velocity Type dialog box.
2
In the Seismic Grid box, enter the name of the Voxet or Seismic Line object that contains the velocity you want to convert.
3
In the Input Velocity Property box, enter the velocity property you want to convert.
4
In the Velocity Type box, select the type of the velocity. Note The voxet or seismic line can be in either the time domain (choose a type from the first four choices) or the depth domain (choose from the last four choices). RMS types are for stacking velocity.
5
In the Velocity Unit box, enter the unit of the input velocity property that you are converting.
6
In the Output Velocity Property box, enter the name of the velocity property obtained by conversion of the input velocity.
7
In the Velocity Type box, select the type of the velocity obtained by the conversion. Important If you selected a two-way time velocity in step 4, you need to select another two-way time velocity type here. If the conversion to be performed is from one domain (time or depth) to another, use the function described in "Converting the Velocity Type in Different Domains" on page 6-3.
8
6-2
Click OK or Apply.
Performing Velocity Conversions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
6.2
Converting the Velocity Type in Different Domains Use this function to convert velocity from one domain to another (time to depth or depth to time). The command creates a seismic grid (Voxet or Seismic Lines object) to contain the converted velocity. Afterward, the seismic grid is in the final domain space (if the initial velocity is in time, the seismic grid will be in the depth domain). Note If you have a license suite that enables the use of multiple processors, you can take advantage of parallel processing for this command by ensuring that you enable the settings in Edit > Preferences > Multicore and GPU Processing. For more information, see Part I: Getting Started, "Setting Multicore and GPU Processing Preferences" on page 2-10.
To convert velocity in different domains
1
Select Velocity commands > Velocity Conversion > Voxet and Seismic Lines: In Different Domains to open the Convert Velocity Type dialog box.
2
In the Seismic Grid box, select the name of the Voxet or Seismic Lines object that carries the velocity to be converted.
3
In the Input velocity property box, enter the velocity property to be converted.
4
In the Velocity type box, select the type of the velocity to be converted. Note The seismic grid can be in either the time domain (choose from the first four types) or the depth domain (choose from the last four types).
User Guide
6.2 Converting the Velocity Type in Different Domains
6-3
5
In the Velocity unit box, select the units in which the velocity is measured:
•
m/s (two-way time). For a seismic grid that is in the time domain, the time required, measured in meters per second, to go from the datum to a given point and back.
•
ft/s (two-way time). For a seismic grid that is in the time domain, the time required, measured in feet per second, to go from the datum to a given point and back.
•
m/s (one-way time). For a seismic grid that is in the time domain, the time required, measured in meters per second, to go from the datum to a given point.
•
ft/s (one-way time). For a seismic grid that is in the time domain, the time required, measured in feet per second, to go from the datum to a given point.
Note For seismic grids in the depth domain, the unit describes the nature of the velocity. Tip In the example in step 6, the depth cube will be between 0 and 7500 m, but you may not want the full cube for the current stage of the modeling. You might only want the subvolume included between 0 and 5000.
Tip In the example in step 6 (sub-volume from 0 to 5000m), the value entered is 5000.
6
In the Output voxet name box, type the name of the Voxet or Seismic Lines object to be created. Since the domain is changing, the converted velocity should be in a different Voxet or Seismic Lines object. Example In the case of conversion from time to depth, if the time cube is between 0 and 6 s and the maximum average velocity is 2500m/s, the depth cube will be between 0 and 7500m (with a conversion factor of 2). Therefore, if the same input Voxet or Seismic Lines obj ect had been used, most of the converted velocity would have fallen outside the input cube.
7
In the Starting Z box, type the starting z-value for the voxet or seismic lines in the final domain.
8
In the Ending Z box, type the final z-value for the voxet or seismic lines in the final domain.
9
In the Number of W steps box, type the number of samples along the depth/time axis.
10 In the Output velocity property box, enter the name of the velocity obtained by conversion. 11 In the Velocity type box, select the type of the velocity obtained by the conversion. Note You need to select a different domain than the one selected in step 4. If you selected a two-way time average velocity in step 4, you need to select a depth type velocity here. If the conversion to be performed is from one domain to another, use the function described in "Converting the Velocity Type in Different Domains" on page 6-3.
12 Select the option that indicates whether the new converted velocity will be stored in memory or on disk: Store in memory or Store on disk. 13 Click OK or Apply.
6-4
Performing Velocity Conversions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
6.3
Converting the Velocity Type of Velocity Functions Use this function to convert the velocity type of a velocity function within one domain (time or depth).
To convert the velocity type of a velocity function
1
Select Velocity commands > Velocity Conversion > Velocity Functions: In One Domain to open the Convert Velocity Type dialog box.
2
In the Velocity functions box, select the velocity function that you want to convert.
3
In the Input velocity property box, select the velocity of the velocity function.
4
In the Output velocity property box, enter the new velocity property.
5
In the Output type box, select the new velocity type.
6
Do one of the following:
7
User Guide
•
If the seismic reference datum (SRD) is constant for the velocity function, then select the Constant SRD check box, and then in the SRD value box, enter the SRD.
•
If the SRD varies, deselect the Constant SRD check box, and then in the 2D-Grid SRD surface box, enter a 2D-grid that represents the SRD value.
Click OK or Apply.
6.3 Converting the Velocity Type of Velocity Functions
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Performing Velocity Conversions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
7 Interpolating Velocity
In this chapter
Overview
•
"Smoothing a Voxet Property," page 7-2
•
"Extracting the Velocity Trend From a Voxet," page 7-4
•
"Interpolating Velocity Linearly Between Surfaces," page 7-3
•
"Extracting the Velocity Trend From a Well Property," page 7-5
The Velocity Interpolation commands enable you to interpolate velocity data. The velocity data can be a property on a voxet, a property on a grid, or a well log.
7-1
7.1
Smoothing a Voxet Property You can use Velocity commands > Apply Median Window/Average Filter to smooth a voxet, stratigraphic, or geologic grid property, such as average velocity, for example. For more information, see Part IV: Foundation Modeling, "To compute a grid property as a median or average of existing property values" on page 10-15.
7-2
Interpolating Velocity
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
7.2
Interpolating Velocity Linearly Between Surfaces You can interpolate the velocity linearly between selected surfaces and store the interpolated velocity as a property of the voxet. The surfaces you select can be horizons or faults that have a velocity property of the same name.
To interpolate velocity linearly between surfaces
1
Select Velocity commands > Velocity Interpolation > Between Surfaces to open the Interpolate Velocity Linearly Between Surfaces (Store in Voxet) dialog box.
2
In the Voxet Velocity Cube box, enter the voxet that carries the velocity.
3
In the Output Velocity Property box, type the name of the new property that will hold the interpolated velocity and will be associated with the voxet.
4
In the Surface List box, enter the horizons or faults between which you want to linearly interpolate the velocity.
5
In the Surface Velocity box, enter the property of the voxet that represents the velocity.
6
Choose one of the following options for the voxet property you create:
• •
User Guide
Stored on memory Stored on disk
7
If you want to extrapolate the values beyond the surfaces you select, select the Extrapolate Values check box.
8
Click OK or Apply.
7.2 Interpolating Velocity Linearly Between Surfaces
7-3
7.3
Extracting the Velocity Trend From a Voxet You can use the Extract Trend from Voxet command to extract a velocity property from a voxet and use it to create a map that contains the velocity trend, which can help you create a velocity model that better represents local variations. The command computes a least squares regression between depth and velocity and creates a map of the regression properties.
To extract velocity from a Voxet
1
Select Velocity commands > Velocity Interpolation > Extract Trend from Voxet to open the Create a Least Squares Coefficients Map dialog box.
2
In the Map name box, type the name of the map that you want to create.
3
In the Voxet box, enter the voxet that has the velocity property.
4
If you want to extract the velocity trend in only a specific region within the voxet, select the Region check box, and then select the region.
5
In the X Property (Z) box, enter the voxet property that represents depth.
6
In the Y Property (Velocity) box, enter the voxet property that represents velocity.
7
In the Least squares Regression Type box, select the regression type, linear or quadratic.
8
If you want to create a property that contains the error between the velocity property and the regression function, select the Create local error check box.
9
The voxet property that contains the error is local_error. To change the property name, in the Error box, type a new name.
10 Click OK or Apply.
7-4
Interpolating Velocity
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
7.4
Extracting the Velocity Trend From a Well Property You can use the Extract Trend from Well(s) command to extract the velocity from one or more well logs and use it to create a PointsSet object that contains the velocity trend, which can help you create a velocity model that better represents local variations. The command computes, for reach well log, a least squares regression between well depth and the well log velocity and creates a PointsSet object that contains the regression properties.
To extract velocity from wells
User Guide
1
Select Velocity commands > Velocity Interpolation > Extract Trend from Well(s) to open the Create a Point Set Holding Velocity Trend dialog box.
2
In the PointSet name box, type the name of the PointsSet object that you want to create to hold the velocity trend properties.
3
In the Well box, enter the wells for which you want to extract the velocity trend.
4
If you want to extract the velocity trend in only a specific region, select the Region check box, and then select the region.
5
In the Y Property (Velocity) box, enter the well log property that represents velocity.
6
In the Least squares Regression Type box, select the regression type, linear or quadratic.
7
Click OK or Apply.
7.4 Extracting the Velocity Trend From a Well Property
7-5
7-6
Interpolating Velocity
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
8 Performing Time and Depth Domain Conversions In this chapter
Overview
•
"Converting Objects Using a Velocity Cube," page 8-2
•
"Converting a Seismic Cube," page 8-4
•
"Reassigning an Object to the Correct Domain," page 8-7
•
"Converting Seismic Lines," page 8-8
•
"Converting a SKUA Model," page 8-10
•
"Rescaling Objects in the Same Domain," page 8-12
The Velocity commands consist of a series of functions that perform velocity conversions and time-to-depth conversions (or depth-to-time conversions). The time-to depth conversion functions in Paradigm™ SKUA ® and Paradigm™ GOCAD ® convert modeling objects from the time domain to the depth domain and vice versa. Velocity can originate from different sources. The Velocity cube can be directly imported, computed from regional data within SKUA or GOCAD by using mathematical functions, or computed from field data (such as well logs, checkshots, stacking velocity, or VRMS) by using geostatistical operations and/or interpolation methods.
8-1
8.1
Converting Objects Using a Velocity Cube Use this function to convert objects (except cross sections, well sections, maps, or SKUA models), from the time domain to the depth domain (or vice versa) by using an average velocity cube. Use the function described in "Converting the Velocity Type in One Domain" on page 6-2 to convert any type of velocity to the required average velocity. The object conversion is a simple vertical stretch using the equation Z = time * velocity.
To convert from one domain to another domain using velocity cube
1
Select Velocity commands > Time-Depth Conversion > Convert Object Using Velocity to open the Convert Objects dialog box.
2
In the Domain Type box, select the domain of the objects that you want to convert.
3
In the Object list box, enter one or more objects to be converted (excluding seismic cubes; see "Converting a Seismic Cube" on page 8-4).
4
If you want to create copies of the objects before converting them, select the Copy the Objects Before Conversion check box. If you want to prefix the names of the copied objects, select the Using Prefix check box, and then in the Prefix box, type the prefix.
5
In the Point property server Velocity volume box, enter the name of the object (voxet, velocity function, stratigraphic grid, or geologic grid) carrying the average velocity. Note The velocity cube should be in same domain as the objects to be converted.
6
8-2
In the Average velocity box, enter the name of the average velocity.
Performing Time and Depth Domain Conversions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
7
8
In the Velocity unit box, select the units in which the velocity is measured:
•
m/s (two-way time). The time required, measured in meters per second, to go from the datum to a given point and back.
•
ft/s (two-way time). The time required, measured in feet per second, to go from the datum to a given point and back.
•
m/s (one-way time). The time required, measured in meters per second, to go from the datum to a given point.
•
ft/s (one-way time). The time required, measured in feet per second, to go from the datum to a given point.
Select the type of seismic reference datum:
• •
User Guide
Constant datum. Equal to a constant. In the Value box, enter the constant. Datum surface. Defined by a Surface or 2D-Grid object. In the 2D-Grid Surface box, enter the Surface or 2D-Grid object to which the seismic is referenced.
8.1 Converting Objects Using a Velocity Cube
8-3
8.2
Converting a Seismic Cube Use this function to convert any attribute of a seismic cube from the time domain to the depth domain (or vice versa) by using an average velocity. Usually, the amplitude is the attribute to be converted. Use the function described in "Converting the Velocity Type in One Domain" on page 6-2 to convert any type of velocity to the required average velocity. This command creates a new seismic cube because the vertical sampling needs to be regular. When the seismic amplitude is converted, the vertical wavelet is resampled between the time and depth domains. Note If you have a license that enables the use of multiple processors, you can take advantage of parallel processing for this command by ensuring that you enable the settings in Edit > Preferences > Multicore and GPU Processing. For more information, see Part I: Getting Started, "Setting Multicore and GPU Processing Preferences" on page 2-10.
To convert Seismic cube to time or to depth using average velocity
8-4
1
Select Velocity commands > Time-Depth Conversion > Seismic Cube Conversion to open the Convert Seismic Cube dialog box.
2
In the Voxet seismic box, enter the name of the Voxet that contains the seismic attribute to be converted.
3
In the Seismic properties box, enter one or more seismic properties to be converted. (Amplitude is the default, but you can choose any other attribute(s).)
Performing Time and Depth Domain Conversions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
Tip In the example in step 8, the depth cube will be between 0 and 7500 m, but you may not want the full cube for the current stage of the modeling. You might only want the subvolume included between 0 and 5000.
4
Select the option indicating the type of conversion to be performed: Time to depth conversion or Depth to time conversion.
5
In the Voxet velocity cube box, enter the name of the Voxet that contains the average velocity. The velocity cube can be in the same domain as the seismic cube, or it can be in another domain.
6
In the Average velocity box, enter the name of the average velocity used during the seismic attribute conversion.
7
In the Velocity unit box, select the units in which the velocity is measured:
8
•
m/s (two-way time). The time required, measured in meters per second, to go from the datum to a given point and back.
•
ft/s (two-way time). The time required, measured in feet per second, to go from the datum to a given point and back.
•
m/s (one-way time). The time required, measured in meters per second, to go from the datum to a given point.
•
ft/s (one-way time). The time required, measured in feet per second, to go from the datum to a given point.
The command creates another voxet to define the degree of deformation (stretching) of the resampled wavelet. Under Output Voxet, specify information about the new voxet as follows: a
In the Output Voxet Name box, type a name for the voxet.
Example In the case of conversion from time to depth, if the time cube is between 0 and 6 s and the maximum average velocity is 2500m/s, the depth cube will be between 0 and 7500m (with a conversion factor of 2). Therefore, if the same input Voxet had been used, most of the converted velocity would have fallen outside the input cube.
Tip In the example in step 8 (sub-volume from 0 to 5000m), the value entered is 5000.
b
In the Starting depth/time box, type the starting z-value for the voxet in the final domain.
c
In the Ending depth/time box, type the final z-value for the voxet in the final domain.
d
In the Number of depth/time steps box, type the number of samples along the depth/time axis. This value corresponds to the number of nodes in the vertical direction in the destination voxet. The command uses this value, the Starting Z value, and the Ending Z value to determine the vertical step of the destination voxet.
User Guide
8.2 Converting a Seismic Cube
8-5
9
Under the Seismic Output Property, specify how you want to create the new property:
a
Click the option that indicates the property size of the voxet: Create as 32 bits, Create as 16 bits, or Create as 8 bits. Note If the property is created as 8 bits, the command reduces the memory used for the display without sacrificing visual accuracy.
b
If you chose Create as 8 bits in step a and you want to define the data spread of the converted property as -127 to 127, select the Is signed check box. Otherwise, the data spread is assumed to be 0 to 255.
c
Select the option that indicates whether the new converted velocity will be stored in memory or on disk: Store in memory or Store on disk. Note If you select Store in memory and the system does not have enough memory, then it puts the properties on disk automatically.
d
In the Interpolation method box, select the interpolation method to use in the conversion that is appropriate for the property type you are using:
• • •
Wavelet. To convert a seismic cube with an amplitude property. Linear. To convert a seismic cube with a velocity property. Closest value. To convert a seismic cube with a facies property.
Note Because voxets have a fixed sampling in each domain, when the position of the values are converted from one domain to another, they do not fall exactly on a node in the destination voxet. Therefore, the command uses the selected interpolation method to estimate the value in the destination voxet.
10 Select the type of seismic reference datum:
• •
Constant datum. Equal to a constant. In the Value box, enter the constant. Datum surface. Defined by a Surface or 2D-Grid object. In the 2D-Grid Surface box, enter the Surface or 2D-Grid object to which the seismic is referenced.
11 Click OK or Apply.
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Performing Time and Depth Domain Conversions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
8.3
Reassigning an Object to the Correct Domain If data objects are loaded, imported, or created in the wrong domain (time or depth), you can reassign the data to the correct domain. Objects in the time domain can be reassigned to the depth domain, and vice versa. For more information, see Part I: Getting Started, "Checking and Correcting Object Units and Domain" on page 3-45.
User Guide
8.3 Reassigning an Object to the Correct Domain
8-7
8.4
Converting Seismic Lines You can convert any attribute of a Seismic Lines object (typically, the amplitude) from the time domain to the depth domain (or vice versa) by using an average velocity. To convert any type of velocity to the required average velocity, use the function described in "Converting the Velocity Type in One Domain" on page 6-2. This command creates a new seismic line because the vertical sampling needs to be regular. Note If you have a license that enables the use of multiple processors, you can take advantage of parallel processing for this command by ensuring that you enable the settings in Edit > Preferences > Multicore and GPU Processing. For more information, see Part I: Getting Started, "Setting Multicore and GPU Processing Preferences" on page 2-10.
To convert Seismic Lines domain using average velocity
1
Select Velocity commands > Time-Depth Conversion > SeismicLines Conversion to open the Convert Seismic Survey dialog box.
2
In the SeismicLine Lines box, enter the name of the Seismic Lines object that contain the seismic attribute to be converted. Note The type of conversion depends of the domain of the Seismic Lines. If the Seismic Lines are in time, SKUA or GOCAD performs a Time-to-Depth conversion. If the Seismic Lines are in depth, SKUA or GOCAD performs a Depth-to-Time conversion.
3
In the Seismic properties box, enter one or more seismic properties to be converted. Amplitude is preselected, but you can choose any other attributes.
4
In the Average velocity box, enter the name of the average velocity used during the seismic attribute conversion. Note The Seismic Line to be converted contains the average velocity properties and the properties to be converted (no other source of velocity data can be used).
5
8-8
In the Velocity unit box, select the units in which the average velocity is measured:
Performing Time and Depth Domain Conversions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
6
•
m/s (two-way time). The time required, measured in meters per second, to go from the datum to a given point and back.
•
ft/s (two-way time). The time required, measured in feet per second, to go from the datum to a given point and back.
•
m/s (one-way time). The time required, measured in meters per second, to go from the datum to a given point.
•
ft/s (one-way time). The time required, measured in feet per second, to go from the datum to a given point.
The command creates another survey to store the data. Specify information to create the new survey as follows: a
In the Output Survey Name box, type the name of the SeismicLines to create. The new SeismicLines defines the extent of either the deformation or stretching of the resampled wavelet.
7
b
In the Starting Z box, type the starting z-value for the SeismicLines in the final domain.
c
In the Ending Z box, type the final z-value for the SeismicLines in the final domain.
d
In the Number of depth/time steps box, type the number of samples along the depth/time axis.
In the Interpolation method box, select the interpolation method to use in the conversion:
• • • 8
User Guide
Wavelet. A sync interpolation used for amplitude-like properties. Linear. Used for velocity-type properties. Closest value. Used for facies-like properties.
Click OK or Apply.
8.4 Converting Seismic Lines
8-9
8.5
Converting a SKUA Model You can convert a SKUA model and related objects (faults, horizons, geologic grid) from the time domain to the depth domain (or vice versa) by using an average velocity. The command creates a copy of the SKUA model. The copy retains all object relationships, such as fault contacts and horizons. The object conversion is a vertical stretch using the Z = time * velocity equation.
To convert the domain of a SKUA model
1
Select Velocity commands > Time-Depth Conversion > Convert SKUA Model and al. to open the Convert SKUA model dialog box.
2
In the SKUA Model box, select the SKUA model to convert.
3
In the Point property server Velocity Cube box, enter the name of the geologic grid, voxet, or velocity function that carries the average velocity. The domain of thee geologic grid, voxet, or the velocity function and the SKUA model you are converting need to be in the same domain.
4
In the Average Velocity box, enter the name of the average velocity property.
5
In the Velocity unit box, select the units in which the velocity is measured:
6
•
m/s (two-way time). The time required, measured in meters per second, to go from the datum to a given point and back.
•
ft/s (two-way time). The time required, measured in feet per second, to go from the datum to a given point and back.
•
m/s (one-way time). The time required, measured in meters per second, to go from the datum to a given point.
•
ft/s (one-way time). The time required, measured in feet per second, to go from the datum to a given point.
Select the type of seismic reference datum:
• •
8-10
Constant. Equal to a constant. In the Value box, enter the constant. Varying. Defined by a Surface or 2D-Grid object. In the 2D-Grid Surface box, enter the Surface or 2D-Grid object to which the seismic is referenced.
Performing Time and Depth Domain Conversions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
7
If you want to convert the SKUA model (with faults), the horizon grids, and the geologic grid, select the Transform attached objects check box. If not checked, the command convert only the structural models (with faults).
8
User Guide
Click OK or Apply.
8.5 Converting a SKUA Model
8-11
8.6
Rescaling Objects in the Same Domain With the Conversion Correction menu commands, you can rescale objects or sesimic cubes in the same domain. For example, you might want to rescale objects and seismic from migrated depth to true depth. From the new information provided by the depth markers, you can create a correction factor property that SKUA or GOCAD uses to rescale your objects. The workflow for rescaling objects is as follows:
8.6.1
1
Create a correction factor from the well marker information.
2
Perform object rescaling.
3
Perform seismic cube rescaling.
Rescaling Objects in Same Domain You can use the following command to rescale an object in the same domain. The object rescaling is a Z conversion:
Z new = Correction Factor Z old where:
Z new Z old
= rescaled depth = initial depth
Correction Factor To rescale objects in same domain
= a correction factor that you calculate from depth markers
1
Select Velocity commands > Conversion Correction > Rescale Objects in Same Domain to open the Rescale Objects dialog box.
2
In the Object List box, enter the objects (any object other than seismic cubes) to be rescaled. Note To rescale a seismic cube, see "To rescale a seismic cube in same domain" on page 8-13.
8-12
Performing Time and Depth Domain Conversions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
3
If you want to create copies of the objects before you rescale them, select the Copy Objects Before Rescaling check box. Note SKUA or GOCAD keeps a copy of the initial objects and creates rescaled objects prefixed with scaled_.
4
In the Point Property server Cube box, enter the name of the voxet, velocity function, or grid that carries the correction factor property that is in the same domain as the objects to be rescaled. Note The Property server cube should be in same domain as the objects to be rescaled.
8.6.2
5
In the Scaling Property box, enter the name of the correction factor property. This property should unitless.
6
Click OK or Apply.
Rescaling a Seismic Cube in Same Domain You can use the following command to rescale a seismic cube in the same domain. Note If you have a license that enables the use of multiple processors, you can take advantage of parallel processing for this command by ensuring that you enable the settings in Edit > Preferences > Multicore and GPU Processing. For more information, see Part I: Getting Started, "Setting Multicore and GPU Processing Preferences" on page 2-10.
To rescale a seismic cube in same domain
User Guide
1
Select Velocity commands > Conversion Correction and then click Seismic Cube Rescaling-Resampling to open the Rescale Seismic Cube dialog box.
2
In the Voxet seismic box, enter the name of the voxet that contains the seismic attribute to be rescaled.
3
In the Seismic properties box, enter one or more seismic properties to be rescaled.
8.6 Rescaling Objects in the Same Domain
8-13
Amplitude is preselected, but you can choose any other attributes. 4
In the Voxet rescaling cube box, enter the name of the voxet that contains the correction factor property. The voxet rescaling cube can be in the same domain as the seismic cube, or it can be in another domain; usually it will be in the same domain.
5
In the Scaling property box, enter the name of the scaling property used to rescale the seismic cube.
6
In the Output voxet name box, type the name of the voxet to create.
7
In the Starting Z box, type the starting z-value for the rescaled voxet (usually it should be the same starting z as the initial voxet).
8
In the Ending Z box, type the final z-value for the rescaled Voxet in the final domain. (usually it should be the same ending z as the initial voxet).
9
In the Number of depth/time steps box, type the number of samples along the depth/time axis (usually it should be the same vertical samples z as the initial voxet).
10 Select whether to store the newly converted velocity in memory or on disk. 11 In the Interpolation method box, select the interpolation method to use in the conversion:
• • •
Wavelet. A sync interpolation used for amplitude-like properties. Linear. Used for velocity-type properties. Closest value. Used for facies-like properties.
12 Click OK or Apply.
8-14
Performing Time and Depth Domain Conversions
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Index
A Add Function menu 4-19 Add Region to Layer dialog box 2-15 add Surface (to Model) 2-7 add surfaces (to VoxetModel) 2-19 Add Surfaces in Model3d dialog box 2-7 Add Surfaces to Voxet Model dialog box 2-20 Annealing Simulation dialog box 5-27 attributes of Model common 2-2
B Bayesian kriging 5-12 Bayesian Kriging dialog box 5-12 Block Velocity Functions on Grid dialog box 4-26 build (Model3d) 2-8 build (Voxet Model) 2-21 Build 3D-Model dialog box 2-8 Build Voxet Model dialog box 2-21
C categorical histogram correction 5-31
Categorical Histogram Correction dialog box 5-31 Change Model Layer name dialog box 2-14 Change Model Region name dialog box 2-17 cloud transform (w/ P-field) 5-29 collocated cokriging estimation 5-14 simulation 5-22 Collocated Cokriging dialog box 5-14 Collocated Cokriging Simulation dialog box 5-23 constant 4-9 constant property variable 4-9 continuous histogram correction 5-32 Continuous Histogram Correction dialog box 5-32 Convert Objects dialog box 8-2 Convert Seismic Cube dialog box 8-4, 8-8 Convert SKUA model dialog box 8-10 Convert Velocity Type dialog box 6-2, 6-3, 6-5 create property function 4-19 Create Curve from Curves dialog box 3-4, 3-6, 3-9 create default LayerSet
Model3d 2-13 Create Default LayerSet inside Model dialog box 2-13 Create Model3d From Surfaces dialog box 2-4 Create new Layer inside Model from an existing Region dialog box 2-13 Create Velocity Functions from Time/Depth Logs dialog box 3-8 CreateModel3d from SKUA Model Horizons, Faults and Boundaries dialog box 2-5
D define property function dir_Z 4-6 direction shoot 4-6
4-19
F FaciesMap Simulation dialog box 5-34 fill grid from facies map 5-34 Filter/Collapse Small Voxet Model Regions dialog box 2-22 from_inside 4-7, 4-17 from_outside 4-7 function
Index-1
property function
4-19
G geostatistics estimation method Bayesian kriging 5-12 collocated cokriging 5-14 indicator kriging 5-16 kriging 5-6 kriging with external drift 5-10 kriging with trend 5-8 simulation methods collocated cokriging 5-22 nonconditional SGS 5-21 SCloud transform 5-29 sequential gaussian simulation 5-18 sequential indicator simulation 5-24 simulated annealing 5-26 tools categorical histogram correction 5-31 continuous histogram correction 5-32 fill grid from facies map 5-34
I impact point 4-8 on bounding surfaces 4-18 on bounding surfaces, Fig. 4-18 on Surfaces for interpolation, Fig. 4-11 indicator kriging 5-16 in Voxet 5-16 Indicator kriging dialog box 5-16
K Kill Surfaces in Model3d dialog box 2-8 kriging 5-6 Kriging dialog box 5-6 Kriging menu in SGrid 5-6
Index-2
kriging with external drift 5-10 Kriging With External Drift dialog box 5-10 kriging with trend 5-8 Kriging With Trend dialog box 5-8
L layer 2-18 display 2-3 linear property function
4-20
M Make Surfaces and Regions Geologically consistent dialog box 2-10 Menu Add Function, see Add Function menu merging fault throws 2-5
N name of a variable in Property Function 4-6 New menu Model 2-2 Non Conditional Simulation dialog box 5-21 nonconditional SGS Voxet simulation 5-21
P painting velocity model 4-25 parameters shoot parameters 4-6 Pfield Simulation dialog box 5-29 property
function 4-19 linear function 4-20 script function 4-23 script function components 4-23 script function examples 4-24 syntax 4-23 Property Model Editor 4-9, 4-27 property variable constant 4-9 from a Surface 4-13 from a Voxet 4-12
R Rebuild 3D-Model dialog box 2-9 Remove Free Horizon Extremities from Model3d dialog box 2-12 Remove Free Horizon Extremities in a given region from Model3d dialog box 2-11 Remove Layer dialog box 2-14 remove Surface (from Model) 2-8 remove surfaces (from VoxetModel) 2-20 Remove Surfaces from Voxet Model dialog box 2-20 Rescale Objects dialog box 8-12 Rescale Seismic Cube dialog box 8-13
S script of property functions 4-23 Select Text File dialog box 5-9, 5-11, 5-15, 5-17, 5-20, 5-22, 5-24, 5-26, 5-28 sequential gaussian simulation 5-18 nonconditional 5-21 Sequential Gaussian Simulation dialog box 5-19 sequential indicator simulation 5-24 Sequential Indicator Simulation dialog box 5-25 shoot direction 4-6
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
Part VI: Velocity Modeling
direction (Fig) 4-7 impact point 4-8 position 4-7 position(Fig) 4-7 shoot parameters 4-6 shooting point 4-7 simulated annealing 5-26 Simulation menu in Voxet 5-18
User Guide
Surface property variable in Model
4-13
V variable name 4-6 Variable Name dialog box variogram
4-5
ASCII file examples 5-3 velocity function, painting on grid 4-26 velocity functions, visualizing 3-5 velocity modeling, painting on grid 4-25 Voxet property variable in Model 4-12
Index-3
Index-4
SKUA® and GOCAD® – Paradigm™ 2011 With Epos® 4.1 Data Management
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